EBB Render Mode
Summary
Designed and implemented a "render mode" feature for Emoji Ball Battles that captures a deterministic weapon-vs-weapon battle as a video file with audio, without requiring interactive play.
Feature Design and Planning:
- Explored the existing engine architecture: headless mode (no window, no rendering), arena's seed/weapon support, the 120Hz physics / 60Hz render split, layer FBO system, and sound_play API
- Discussed two rendering approaches: (A) visible window with frame capture vs (B) offscreen/hidden window. Chose A (simpler, existing rendering code works as-is)
- Decided on YueScript monkey-patching for sound logging (over C-level hooks) — wraps
an.sound_play,an.sound_play_handle,an.sound_handle_set_pitch,an.sound_handle_set_volume - For dynamic-pitch sounds (thrust weapon uses
sound_play_handlewith per-frame pitch changes), chose piecewise constant approximation: split the sound into ~10 time chunks, apply average pitch per chunk via ffmpegasetrate, concatenate into a single baked .ogg file - Named the feature
--render(discussed alternatives:--capture,--record,--replay) - Added 3 seconds of post-battle capture to avoid abrupt video endings
Engine C Changes (anchor.c):
- Added
stb_image_write.htoAnchor/engine/include/stb/(downloaded from stb GitHub repo) - Added render mode globals:
render_mode,capture_fbo,capture_texture,capture_buffer,capture_frame_number,capture_output_dir - Added
--renderCLI flag parsing alongside--headless - Disabled vsync in render mode for max speed
- Added 3 new Lua bindings:
engine_get_render_mode(),engine_render_setup(dir),engine_render_save_frame() - Created a new deterministic render loop: 2 physics steps per frame, automatic capture pass (composite layers to FBO at native 480x270 → glReadPixels → vertical flip → stbi_write_png), then screen pass for visual feedback
- Capture FBO renders at native 480x270 resolution (not the scaled window size), using the same layer_draw_queue compositing as the normal screen pass
Framework Changes (anchor/init.yue):
- Exposed
an.render_mode = engine_get_render_mode! - Added
an.sound_paths = {}table, populated byan.sound()to store name→path mappings for sound file lookup during audio assembly
Game Logic (main.yue):
- New
if an.render_mode ... elseif an.headlessblock - Sound monkey-patching: intercepts all sound_play/sound_play_handle/sound_handle_set_pitch/sound_handle_set_volume calls, logs events with frame numbers
- Arena creation with seed/weapons from CLI args
- Battle watcher with 3-second post-battle delay (180 frames)
- Sound log written as
sounds.lua
Audio Assembly (ffmpeg):
- Phase 1: Pre-processes handle-based sounds (dynamic pitch) into baked .ogg files using piecewise ffmpeg
atrim→asetrate→aresample→concat - Phase 2: Mixes all sounds via ffmpeg
amixwith batching (groups of 50 streams → intermediate WAVs → final mix) - Fixed a critical bug: batch filter scripts referenced global input indices (e.g.,
[50:a]) instead of local (0-based per batch), causing all batches except the first to produce empty WAVs - Fixed
amixvolume normalization: addednormalize=0to prevent automatic volume division by input count (was making sounds extremely quiet and causing volume drift as sounds finished)
ffmpeg % Escaping Issue:
frame_%06d.pngin Luaos.executewas failing because YueScript string interpolation (#{}) processed the%character- Fix: used raw Lua string concatenation (
..) instead of YueScript interpolation for strings containing%, bypassing the escaping issue entirely
Video Encoding:
- Frames encoded at 1920x1080 (4x nearest-neighbor upscale via
scale=1920:1080:flags=neighbor) - libx264, CRF 18, AAC audio at 192k
- Typical output: ~10MB for a 77-second battle
Generated File Organization:
- Render intermediates (PNGs, WAVs, filter scripts, sounds.lua, video_only.mp4) moved to
E:/a327ex/emoji-ball-battles-generated/renders/{matchup}/ - Only
battle.mp4stays in the localrenders/directory - Headless results:
.dat,.luafiles moved toemoji-ball-battles-generated/results/, only.htmlreports remain in localresults/ - Manual initial cleanup: moved existing
.dat/.luafiles from results/ to generated mirror
Invocation:
bash
cd E:/a327ex/emoji-ball-battles
./anchor.exe . --render --matchup=saw,boomerang --seed=7
Let's work on a feature for Emoji Ball Battles where we'll render a specific weapon vs. weapon seed as a video without having to run the game. This feature will capture every frame of the battle as a picture, log every sound that happens every frame, along with its pitch and volume, then use ffmpeg to create a video of the battle. We'll use 480x270 resolution for the pictures, and then increase that in the end to 1920x1080 when generating the final video, a simple 4x integer scale. Any questions?
Opus 4.6
[Think]
The user wants to build a feature for Emoji Ball Battles that renders a specific weapon vs. weapon battle as a video without running the game interactively. Let me break down what they're describing:
1. Run a battle simulation with a specific seed (deterministic)
2. Capture every frame as an image (480x270)
3. Log every sound event per frame (sound name, pitch, volume)
4. Use ffmpeg to combine frames into a video at 1920x1080 (4x upscale)
5. Mix in the audio based on the logged sound events
I have several questions about this. Let me think about what I need to understand:
- How the engine works, the rendering pipeline, how battles work with seeds, and whether it supports headless frame capture
- Where sounds are triggered in the code so I can intercept and log them
- How to reconstruct audio from the logged sound events using FFmpeg
I should read through the codebase first to ask informed questions rather than guessing.Good idea — let me read the relevant files first so I can ask informed questions.
Read (E:\a327ex\website\notes\Anchor Engine Overview.md)
File does not exist. Note: your current working directory is E:\a327ex.
Read (E:\a327ex\emoji-ball-battles\docs\FRAMEWORK_API_QUICK.md)
<tool_use_error>Sibling tool call errored</tool_use_error>
Read (E:\a327ex\emoji-ball-battles\main.yue)
<tool_use_error>Sibling tool call errored</tool_use_error>Let me find the correct paths.
Glob (*/Anchor Engine Overview)
E:\a327ex\anchor.blot.im\notes\Anchor Engine Overview.md
Glob (*/emoji-ball-battles/docs/)
E:\a327ex\emoji-ball-battles\docs\PHASE2_WEAPONS.md
E:\a327ex\emoji-ball-battles\docs\ENGINE_API_QUICK.md
E:\a327ex\emoji-ball-battles\docs\ENGINE_API.md
E:\a327ex\emoji-ball-battles\docs\FRAMEWORK_API_QUICK.md
E:\a327ex\emoji-ball-battles\docs\FRAMEWORK_API.md
E:\a327ex\emoji-ball-battles\docs\WEAPON_DESIGN.md
E:\a327ex\emoji-ball-battles\docs\ATTACK_REFERENCE.md
Glob (**/emoji-ball-battles/main.yue)
E:\a327ex\emoji-ball-battles\main.yue
Read (E:\a327ex\anchor.blot.im\notes\Anchor Engine Overview.md)
1→Generated by Claude (Opus 4.5)
2→
3→---
4→
5→# Anchor Engine Overview
6→
7→Anchor is a 2D game engine for solo indie developers. It combines a C core with YueScript (a language that compiles to Lua) for game logic. The engine handles rendering, physics, audio, and input while the framework provides high-level abstractions for building games quickly.
8→
9→---
10→
11→## Core Philosophy
12→
13→**Locality** — Everything about a game object lives in one place. No scattered configuration files, no registering components in separate systems. A class definition contains its properties, behaviors, children, and cleanup logic together.
14→
15→**No bureaucracy** — No imports, no dependency injection, no boilerplate. Resources are registered once and accessed globally. Things work without setup.
16→
17→**YueScript** — A clean syntax that compiles to Lua. Classes, `@` for self-reference, significant whitespace, operator overloading. Pleasant to read and write.
18→
19→---
20→
21→## Architecture
22→
23→```
24→┌─────────────────────────────────────────┐
25→│ Game Code (YueScript) │
26→│ - Your game objects and logic │
27→├─────────────────────────────────────────┤
28→│ Framework (YueScript) │
29→│ - object, layer, timer, collider, etc. │
30→├─────────────────────────────────────────┤
... [601 more lines]
Read (E:\a327ex\emoji-ball-battles\docs\FRAMEWORK_API_QUICK.md)
1→# Framework API Quick Reference
2→
3→Function signatures for YueScript framework classes. See `FRAMEWORK_API.md` for detailed documentation with examples.
4→
5→## Initialization
6→
7→```
8→require('anchor')
9→ width: 640 -- game resolution width (default: 480)
10→ height: 360 -- game resolution height (default: 270)
11→ title: "My Game" -- window title (default: "Anchor")
12→ scale: 2 -- initial window scale (default: 3)
13→ vsync: true -- vertical sync (default: true)
14→ fullscreen: false -- start fullscreen (default: false)
15→ resizable: true -- window resizable (default: true)
16→ filter: "rough" -- "rough" or "smooth" (default: "rough")
17→```
18→
19→## Root Object (an)
20→
21→### Engine State (Static)
22→```
23→an.width -> int -- game resolution width
24→an.height -> int -- game resolution height
25→an.dt -> number -- fixed delta time (1/120)
26→an.platform -> string -- "web" or "windows"
27→```
28→
29→### Engine State (Dynamic - updated every frame)
30→```
... [622 more lines]
Read (E:\a327ex\emoji-ball-battles\main.yue)
File content (68672 tokens) exceeds maximum allowed tokens (25000). Please use offset and limit parameters to read specific portions of the file, or use the GrepTool to search for specific content.The main.yue file is too large to read at once. Let me look at key parts — how battles work, how sound is played, and the rendering pipeline.
Grep (sound_play)
680: an\sound_play 'ball_ball', 0.4, an.random\float(0.95, 1.05)
767: an\sound_play 'dagger_wall', 0.54, an.random\float(0.95, 1.05)
798: an\sound_play 'ball_wall', 0.4, pitch*an.random\float(0.95, 1.05)
811: an\sound_play "grass_impact_#{an.random\int(1, 3)}", 0.5, an.random\float(0.95, 1.05)
824: an\sound_play "concrete_#{an.random\int(1, 3)}", 0.7, an.random\float(0.95, 1.05)
825: -- an\sound_play "arrow_hit_wall_#{an.random\int(1, 2)}", 0.35, an.random\float(0.95, 1.05)
899: an\sound_play "weapon_projectile_#{an.random\int(1, 2)}", 1.0, an.random\float(0.95, 1.05)
979: an\sound_play "concrete_#{an.random\int(1, 3)}", 0.7, an.random\float(0.95, 1.05)
996: an\sound_play "wood_heavy_#{an.random\int(1, 3)}", an.random\float(0.46, 0.74), an.random\float(0.95, 1.05)
1024: an\sound_play "weapon_projectile_#{an.random\int(1, 2)}", 0.85, an.random\float(0.85, 0.9)
1067: an\sound_play 'sword_impact_dirt', 0.78, an.random\float(0.95, 1.05)
1139: an\sound_play "saw_hit#{an.random\int(1, 2)}", an.random\float(0.61, 0.87), an.random\float(0.95, 1.05)
1161: an\sound_play "grass_land_#{an.random\int(1, 3)}", 0.75, an.random\float(0.95, 1.05)
1173: an\sound_play "grass_land_#{an.random\int(1, 3)}", 0.75, an.random\float(0.95, 1.05)
1182: an\sound_play "grass_land_#{an.random\int(1, 3)}", 0.75, an.random\float(0.95, 1.05)
1189: an\sound_play "grass_land_#{an.random\int(1, 3)}", 0.75, an.random\float(0.95, 1.05)
1722: an\sound_play "sword_swing_#{an.random\int(1, 4)}", 0.7, an.random\float(0.95, 1.05)
1778: an\sound_play "bow_draw_#{an.random\int(1, 3)}", 1.0, an.random\float(0.95, 1.05)
1805: an\sound_play "dagger_swing_#{an.random\int(1, 5)}", 0.7, an.random\float(0.95, 1.05)
1821: an\sound_play 'hop', 0.5, an.random\float(0.95, 1.05)
1985: an\sound_play 'dagger_ball', 0.88, an.random\float(0.95, 1.05)
2005: an\sound_play 'player_death', 0.44, an.random\float(0.95, 1.05)
2053: an\sound_play "gun_fire_#{an.random\int(1, 3)}", 0.63, an.random\float(0.95, 1.05)
2122: @thrust_sound_handle = an\sound_play_handle 'wind_small_impact_1', 0.65, @thrust_sound_start_pitch
2207: an\sound_play "arrow_hit_wall_2", 0.9, an.random\float(0.85, 1.15)
3292: an\sound_play "dagger_swing_#{an.random\int(1, 5)}", volume, an.random\float(0.95, 1.05)
3713: an\sound_play "grass_land_#{an.random\int(1, 3)}", 0.75, an.random\float(1.3, 1.4)
[Showing results with pagination = limit: 30, offset: 0]
Grep (class arena|class battle|class fight)
330-
331-
332--- Arena class (contains walls, manages fight state)
333:class arena extends object
334- new: (args={}) =>
335- super 'arena'
336-
Grep (seed)
91:an\image 'seedling', 'assets/seedling.png'
337: -- headless: seed RNG for deterministic battles
338: if args.seed
339: an.random\set_seed args.seed
1249: seedling: {
1274: {left: -10, right: 12} -- Group 1: seedling 12 + sheaf 16
1275: {left: -10, right: 12} -- Group 2: seedling 12 + seedling 16
1276: {left: -14, right: 16} -- Group 3: sheaf 12 + seedling 22 + sheaf 16
1277: {left: -17, right: 14} -- Group 4: blossom 22 + seedling 12
1278: {left: -21, right: 19} -- Group 5: sheaf 18 + tulip 22 + seedling 14
1279: {left: -24, right: 19} -- Group 6: sheaf 16 + four_leaf_clover 19 + seedling 14
1280: {left: -24, right: 38} -- Group 7: sheaf 16 + blossom 22 + seedlings + sheaf 16
1366: -- Group 1: seedling 12 at x-4, sheaf 16 at x+4
1368: @plants\add plant x - 4, y + 0, {image: 'seedling', w: 12, h: 12, layer: front}
1370: -- Group 2: seedling 12 at x-4 (back), seedling 16 at x+4 (front)
1372: @plants\add plant x - 4, y + 0, {image: 'seedling', w: 12, h: 12, layer: back}
1373: @plants\add plant x + 4, y + 0, {image: 'seedling', w: 16, h: 16, layer: front}
1374: -- Group 3: sheaf 12 at x-8 (back), seedling 22 at x (back), sheaf 16 at x+8 (back)
1377: @plants\add plant x + 0, y + 0, {image: 'seedling', w: 22, h: 22, layer: back}
1379: -- Group 4: blossom 22 at x-6 (front), seedling 12 at x+8 (back)
1382: @plants\add plant x + 8, y + 0, {image: 'seedling', w: 12, h: 12, layer: back}
1383: -- Group 5: sheaf 18 at x-12 (back), tulip 22 at x (front), seedling 14 at x+12 (front)
1387: @plants\add plant x + 12, y + 0, {image: 'seedling', w: 14, h: 14, layer: front}
1388: -- Group 6: sheaf 16 at x-16 (front), four_leaf_clover 19 at x (back), seedling 14 at x+12 (front)
1392: @plants\add plant x + 12, y + 0, {image: 'seedling', w: 14, h: 14, layer: front}
1393: -- Group 7: sheaf 16 at x-16 (front), blossom 22 at x (back), seedling 12 at x+4 (front), seedling 12 at x+14 (front), sheaf 16 at x+30 (front)
1397: @plants\add plant x + 4, y + 0, {image: 'seedling', w: 12, h: 12, layer: front}
1398: @plants\add plant x + 14, y + 0, {image: 'seedling', w: 12, h: 12, layer: front}
3607: @image = an.images[args.image or 'seedling']
3872: f\write " seed=#{r.seed}, winner='#{r.winner}',\n"
... [2 more lines]
Grep (\render|\draw!)
265: bg\render!
266: back\render!
267: game\render!
268: front\render!
269: cover\render!
270: weapons\render!
271: outline_only\render!
272: effects\render!
273: recolor_blue\render!
274: recolor_yellow\render!
275: ui\render!
276: debug_draw\render!
311: bg\draw!
313: back_outline\draw!
314: back\draw!
315: game_outline\draw!
316: game\draw!
317: front_outline\draw!
318: front\draw!
319: cover\draw!
320: weapons_outline\draw!
321: weapons\draw!
322: actual_outline_only\draw!
324: effects_outline\draw!
325: effects\draw!
326: ui_outline\draw!
327: ui\draw!
328: debug_draw\draw!
[Showing results with pagination = limit: 30, offset: 0]
Read (E:\a327ex\emoji-ball-battles\main.yue)
330→
331→
332→-- Arena class (contains walls, manages fight state)
333→class arena extends object
334→ new: (args={}) =>
335→ super 'arena'
336→
337→ -- headless: seed RNG for deterministic battles
338→ if args.seed
339→ an.random\set_seed args.seed
340→
341→ @\add object 'effects'
342→ @\add object 'projectiles'
343→ @\add timer!
344→
345→ -- Play area dimensions (200x200, centered)
346→ @w, @h = 200, 200
347→ @x = (gw - @w)/2
348→ @y = (gh - @h)/2
349→ wall_thickness = 200
350→
351→ -- Create walls as children (top, bottom/floor, left, right)
352→ -- Create walls as children (top, bottom/floor, left, right)
353→ -- Floor is only arena width; side walls extend down to cover the rest
354→ @\add wall @x + @w/2, @y - wall_thickness/2, @w + wall_thickness*2, wall_thickness
355→ @\add wall @x + @w/2, @y + @h + wall_thickness/2, @w, wall_thickness, nil, true
356→ @\add wall @x - wall_thickness/2, @y + @h/2 + wall_thickness/2, wall_thickness, @h + wall_thickness
357→ @\add wall @x + wall_thickness/2 + @w, @y + @h/2 + wall_thickness/2, wall_thickness, @h + wall_thickness
358→
359→ -- Create balls
... [70 more lines]
Read (E:\a327ex\emoji-ball-battles\main.yue)
230→an\music 'bgm', 'assets/batoru_umi_to_mamono_no_kodomo_tachi.ogg'
231→an\music 'enbudai', 'assets/enbudai.ogg'
232→an\music_set_volume 0.8
233→
234→an\physics_init!
235→an\physics_set_gravity 0, 384
236→an\physics_tag 'wall'
237→an\physics_tag 'ball'
238→an\physics_tag 'weapon'
239→an\physics_tag 'weapon_hitbox'
240→an\physics_tag 'plant_ghost'
241→an\physics_tag 'projectile'
242→an\physics_collision 'ball', 'wall'
243→an\physics_collision 'ball', 'ball'
244→an\physics_collision 'weapon', 'weapon'
245→an\physics_tag 'projectile_sensor'
246→an\physics_collision 'projectile', 'wall'
247→an\physics_collision 'projectile', 'weapon'
248→an\physics_sensor 'projectile_sensor', 'ball'
249→an\physics_sensor 'projectile_sensor', 'plant_ghost'
250→an\physics_tag 'spiral_projectile'
251→an\physics_collision 'spiral_projectile', 'wall'
252→an\physics_tag 'spiral_weapon_sensor'
253→an\physics_sensor 'spiral_weapon_sensor', 'weapon'
254→an\physics_tag 'boomerang_projectile'
255→an\physics_collision 'boomerang_projectile', 'wall'
256→an\physics_tag 'boomerang_sensor'
257→an\physics_sensor 'boomerang_sensor', 'ball'
258→an\physics_sensor 'boomerang_sensor', 'plant_ghost'
259→an\physics_sensor 'weapon_hitbox', 'ball'
... [80 more lines]
Grep (headless|capture|screenshot|frame_capture)
<persisted-output>
Output too large (23.7KB). Full output saved to: C:\Users\adn\.claude\projects\E--a327ex\2fb57fa1-2576-400f-8ba2-06dc889756ad\tool-results\toolu_0149GzEcWnMRdVxLWUVArYBM.txt
Preview (first 2KB):
334- new: (args={}) =>
335- super 'arena'
336-
337: -- headless: seed RNG for deterministic battles
338- if args.seed
339- an.random\set_seed args.seed
340-
--
357- @\add wall @x + wall_thickness/2 + @w, @y + @h/2 + wall_thickness/2, wall_thickness, @h + wall_thickness
358-
359- -- Create balls
360: headless_player_weapon = args.player_weapon or 'saw'
361: headless_enemy_weapon = args.enemy_weapon or 'boomerang'
362: @player_ball = ball @x + @w*0.25, @y + @h/2, 'player', headless_player_weapon
363: @enemy_ball = ball @x + @w*0.75, @y + @h/2, 'enemy', headless_enemy_weapon
364- @\add @player_ball
365- @\add @enemy_ball
366-
--
388-
389- @paused = false
390-
391: -- headless: battle tracking
392: @headless_battle_over = false
393: @headless_winner = nil
394: @headless_winner_hp = 0
... [24 more lines]
Grep (headless|screenshot|save_image|write_png|save_png|capture_frame)
E:\a327ex\Anchor\engine\src\anchor.c:81:static bool headless_mode = false; // Headless mode: no window, no rendering, max speed
E:\a327ex\Anchor\engine\src\anchor.c:764: // Decode image from memory (needed for width/height even in headless)
E:\a327ex\Anchor\engine\src\anchor.c:781: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:1086: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:1189: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:1294: if (!audio_initialized || !sound || headless_mode) return -1;
E:\a327ex\Anchor\engine\src\anchor.c:1387: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:1444: if (!audio_initialized || !music || !music->initialized || headless_mode) return;
E:\a327ex\Anchor\engine\src\anchor.c:1598: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:1720: if (!headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:5085: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:5104: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:5222: if (headless_mode) return 0;
E:\a327ex\Anchor\engine\src\anchor.c:5230: if (headless_mode) return 0;
E:\a327ex\Anchor\engine\src\anchor.c:5253: if (headless_mode) return 0;
E:\a327ex\Anchor\engine\src\anchor.c:5270: if (headless_mode) return 0;
E:\a327ex\Anchor\engine\src\anchor.c:5302: if (headless_mode) return 0;
E:\a327ex\Anchor\engine\src\anchor.c:7802:static int l_engine_set_headless(lua_State* L) {
E:\a327ex\Anchor\engine\src\anchor.c:7804: return luaL_error(L, "engine_set_headless must be called before engine_init");
E:\a327ex\Anchor\engine\src\anchor.c:7806: headless_mode = lua_toboolean(L, 1);
E:\a327ex\Anchor\engine\src\anchor.c:7810:static int l_engine_get_headless(lua_State* L) {
E:\a327ex\Anchor\engine\src\anchor.c:7811: lua_pushboolean(L, headless_mode);
E:\a327ex\Anchor\engine\src\anchor.c:7837: if (headless_mode) {
E:\a327ex\Anchor\engine\src\anchor.c:7841: printf("Engine initialized (headless): %dx%d\n", game_width, game_height);
E:\a327ex\Anchor\engine\src\anchor.c:8218: lua_register(L, "engine_set_headless", l_engine_set_headless);
E:\a327ex\Anchor\engine\src\anchor.c:8219: lua_register(L, "engine_get_headless", l_engine_get_headless);
E:\a327ex\Anchor\engine\src\anchor.c:8226:// Note: 'running' is declared at file scope (near headless_mode) so engine_quit() can access it
E:\a327ex\Anchor\engine\src\anchor.c:9175: if (strcmp(argv[i], "--headless") == 0) {
E:\a327ex\Anchor\engine\src\anchor.c:9176: headless_mode = true;
E:\a327ex\Anchor\engine\src\anchor.c:9212: // Initialize SDL (headless only needs timer, not video/audio/gamepad)
... [12 more lines]Good — the engine already has a headless mode and the arena already supports seed/weapon parameters. Now let me look at what the headless mode actually does and how the current battle tracking works, plus check for any existing frame capture capability.
Read (E:\a327ex\Anchor\engine\src\anchor.c)
7795→ if (engine_initialized) {
7796→ return luaL_error(L, "engine_set_resizable must be called before engine_init");
7797→ }
7798→ window_resizable = lua_toboolean(L, 1);
7799→ return 0;
7800→}
7801→
7802→static int l_engine_set_headless(lua_State* L) {
7803→ if (engine_initialized) {
7804→ return luaL_error(L, "engine_set_headless must be called before engine_init");
7805→ }
7806→ headless_mode = lua_toboolean(L, 1);
7807→ return 0;
7808→}
7809→
7810→static int l_engine_get_headless(lua_State* L) {
7811→ lua_pushboolean(L, headless_mode);
7812→ return 1;
7813→}
7814→
7815→static int l_engine_get_args(lua_State* L) {
7816→ lua_newtable(L);
7817→ for (int i = 0; i < cli_arg_count; i++) {
7818→ lua_pushstring(L, cli_args[i].value);
7819→ lua_setfield(L, -2, cli_args[i].key);
7820→ }
7821→ return 1;
7822→}
7823→
7824→static int l_engine_quit(lua_State* L) {
... [50 more lines]
Grep (headless_battle_over|headless_step|headless_winner)
389- @paused = false
390-
391- -- headless: battle tracking
392: @headless_battle_over = false
393: @headless_winner = nil
394: @headless_winner_hp = 0
395- @headless_events = {}
396: @headless_step_count = 0
397-
398- -- Clouds (background decoration) using Poisson disk sampling
399- cloud_image = an.images.cloud
--
749- ball_b.collider\set_angular_velocity math.sign(av_b)*ball_b.max_angular_velocity
750-
751- -- headless: log parry event
752: @headless_events[] = {step: @headless_step_count, type: 'parry', ball_a: ball_a.team, ball_b: ball_b.team, weapon_a: ball_a.weapon_type, weapon_b: ball_b.weapon_type}
753-
754- -- Flash both weapons
755- ball_a\flash_weapon!
--
870-
871- -- headless: log projectile parry
872- headless_projectile_owner = if projectile_object.team == 'player' then @player_ball else @enemy_ball
873: @headless_events[] = {step: @headless_step_count, type: 'parry', ball_a: ball_object.team, ball_b: headless_projectile_owner.team, weapon_a: ball_object.weapon_type, weapon_b: headless_projectile_owner.weapon_type}
874-
875- -- Flash and spring pull on weapon (same as weapon-weapon)
876- ball_object\flash_weapon!
--
924- owner.weapon_ui\landed_hit! if owner.weapon_ui
925-
... [84 more lines]Interesting — there's already a headless mode in the engine, and the arena already accepts seed/weapon args for headless battles. Let me look deeper at the existing headless infrastructure and what it currently does vs. what we'd need.
Grep (headless)
<persisted-output>
Output too large (23.5KB). Full output saved to: C:\Users\adn\.claude\projects\E--a327ex\2fb57fa1-2576-400f-8ba2-06dc889756ad\tool-results\toolu_01PQVE1Tw9XgWHMKaa4qrDhr.txt
Preview (first 2KB):
334- new: (args={}) =>
335- super 'arena'
336-
337: -- headless: seed RNG for deterministic battles
338- if args.seed
339- an.random\set_seed args.seed
340-
--
357- @\add wall @x + wall_thickness/2 + @w, @y + @h/2 + wall_thickness/2, wall_thickness, @h + wall_thickness
358-
359- -- Create balls
360: headless_player_weapon = args.player_weapon or 'saw'
361: headless_enemy_weapon = args.enemy_weapon or 'boomerang'
362: @player_ball = ball @x + @w*0.25, @y + @h/2, 'player', headless_player_weapon
363: @enemy_ball = ball @x + @w*0.75, @y + @h/2, 'enemy', headless_enemy_weapon
364- @\add @player_ball
365- @\add @enemy_ball
366-
--
388-
389- @paused = false
390-
391: -- headless: battle tracking
392: @headless_battle_over = false
393: @headless_winner = nil
394: @headless_winner_hp = 0
... [24 more lines]
Read (E:\a327ex\Anchor\engine\src\anchor.c)
7795→ if (engine_initialized) {
7796→ return luaL_error(L, "engine_set_resizable must be called before engine_init");
7797→ }
7798→ window_resizable = lua_toboolean(L, 1);
7799→ return 0;
7800→}
7801→
7802→static int l_engine_set_headless(lua_State* L) {
7803→ if (engine_initialized) {
7804→ return luaL_error(L, "engine_set_headless must be called before engine_init");
7805→ }
7806→ headless_mode = lua_toboolean(L, 1);
7807→ return 0;
7808→}
7809→
7810→static int l_engine_get_headless(lua_State* L) {
7811→ lua_pushboolean(L, headless_mode);
7812→ return 1;
7813→}
7814→
7815→static int l_engine_get_args(lua_State* L) {
7816→ lua_newtable(L);
7817→ for (int i = 0; i < cli_arg_count; i++) {
7818→ lua_pushstring(L, cli_args[i].value);
7819→ lua_setfield(L, -2, cli_args[i].key);
7820→ }
7821→ return 1;
7822→}
7823→
7824→static int l_engine_quit(lua_State* L) {
... [30 more lines]
Grep (save_screenshot|write_pixels|read_pixels|glReadPixels|screenshot)
No matches found
Read (C:\Users\adn.claude\projects\E--a327ex\2fb57fa1-2576-400f-8ba2-06dc889756ad\tool-results\toolu_01PQVE1Tw9XgWHMKaa4qrDhr.txt)
1→334- new: (args={}) =>
2→335- super 'arena'
3→336-
4→337: -- headless: seed RNG for deterministic battles
5→338- if args.seed
6→339- an.random\set_seed args.seed
7→340-
8→--
9→357- @\add wall @x + wall_thickness/2 + @w, @y + @h/2 + wall_thickness/2, wall_thickness, @h + wall_thickness
10→358-
11→359- -- Create balls
12→360: headless_player_weapon = args.player_weapon or 'saw'
13→361: headless_enemy_weapon = args.enemy_weapon or 'boomerang'
14→362: @player_ball = ball @x + @w*0.25, @y + @h/2, 'player', headless_player_weapon
15→363: @enemy_ball = ball @x + @w*0.75, @y + @h/2, 'enemy', headless_enemy_weapon
16→364- @\add @player_ball
17→365- @\add @enemy_ball
18→366-
19→--
20→388-
21→389- @paused = false
22→390-
23→391: -- headless: battle tracking
24→392: @headless_battle_over = false
25→393: @headless_winner = nil
26→394: @headless_winner_hp = 0
27→395: @headless_events = {}
28→396: @headless_step_count = 0
29→397-
30→398- -- Clouds (background decoration) using Poisson disk sampling
... [474 more lines]Now let me look at the end of the file to see how the visual (non-headless) mode starts, and check what the engine's rendering mode actually does in headless (it skips all rendering):
Read (E:\a327ex\emoji-ball-battles\main.yue)
4527→else
4528→ visual_args = {}
4529→ if an.args
4530→ visual_args.seed = tonumber(an.args.seed) if an.args.seed
4531→ if an.args.matchup
4532→ visual_args.player_weapon, visual_args.enemy_weapon = an.args.matchup\match('(%w+),(%w+)')
4533→ an\add arena {seed: 7} -- visual_args
4534→
Read (E:\a327ex\Anchor\engine\src\anchor.c)
5080→ return 0;
5081→}
5082→
5083→// Effect shader Lua bindings
5084→static int l_shader_load_file(lua_State* L) {
5085→ if (headless_mode) {
5086→ // Headless: return dummy shader ID (1) so Lua code doesn't get nil
5087→ lua_pushinteger(L, 1);
5088→ return 1;
5089→ }
5090→ const char* path = luaL_checkstring(L, 1);
5091→ GLuint shader = effect_shader_load_file(path);
5092→ if (!shader) {
5093→ return luaL_error(L, "Failed to load effect shader: %s", path);
5094→ }
5095→ // Register for cleanup on shutdown
5096→ if (effect_shader_count < MAX_EFFECT_SHADERS) {
5097→ effect_shader_registry[effect_shader_count++] = shader;
5098→ }
5099→ lua_pushinteger(L, (lua_Integer)shader);
5100→ return 1;
5101→}
5102→
5103→static int l_shader_load_string(lua_State* L) {
5104→ if (headless_mode) {
5105→ lua_pushinteger(L, 1);
5106→ return 1;
5107→ }
5108→ const char* source = luaL_checkstring(L, 1);
5109→ GLuint shader = effect_shader_load_string(source);
... [10 more lines]
Read (E:\a327ex\Anchor\engine\src\anchor.c)
1080→ if (glyph_h > row_height) row_height = glyph_h;
1081→ }
1082→
1083→ FT_Done_Face(face);
1084→ free(font_data); // Font data no longer needed after face processing
1085→
1086→ if (headless_mode) {
1087→ // Headless: glyph metrics are loaded, skip GL atlas upload
1088→ font->atlas_texture = 0;
1089→ free(rgba_bitmap);
1090→ } else {
1091→ // Create OpenGL texture from RGBA atlas
1092→ // Use appropriate filtering based on mode
1093→ GLint tex_filter = (filter_mode == FILTER_ROUGH) ? GL_NEAREST : GL_LINEAR;
1094→ glGenTextures(1, &font->atlas_texture);
1095→ glBindTexture(GL_TEXTURE_2D, font->atlas_texture);
1096→ glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, FONT_ATLAS_SIZE, FONT_ATLAS_SIZE, 0,
1097→ GL_RGBA, GL_UNSIGNED_BYTE, rgba_bitmap);
1098→ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, tex_filter);
1099→ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, tex_filter);Now let me check the game's init and resolution setup, and understand the layer/FBO system to see what we'd need for frame capture:
Read (E:\a327ex\emoji-ball-battles\main.yue)
1→global *
2→
3→require('anchor')
4→ width: 480
5→ height: 270
6→ scale: 3
7→
8→-- Game dimensions
9→gw, gh = an.width, an.height
10→
11→
12→-- Twitter emoji color palette
13→white = color 255, 255, 255
14→black = color 0, 0, 0
15→gray = color 128, 128, 128
16→bg_color = color 48, 49, 50
17→fg = color 231, 232, 233
18→fg_dark = color 201, 202, 203
19→yellow = color 253, 205, 86
20→star_yellow = color 255, 172, 51
21→orange = color 244, 146, 0
22→blue = color 83, 175, 239
23→green = color 122, 179, 87
24→red = color 223, 37, 64
25→purple = color 172, 144, 216
26→brown = color 193, 105, 79
27→bowstring = color 217, 158, 130
28→debug_draw_enabled = false
29→wall_color = fg\clone!\mix yellow, 0.1
30→
... [20 more lines]
Grep (l_layer_render|l_engine_present|engine_present|swap_window|glReadPixels|fbo_read)
5266-
5267-// Render a layer's queued commands to its FBO (with clear)
5268-// This is called explicitly from Lua draw() instead of automatically
5269:static int l_layer_render(lua_State* L) {
5270- if (headless_mode) return 0;
5271- Layer* layer = (Layer*)lua_touserdata(L, 1);
5272-
--
8064- lua_register(L, "layer_get_texture", l_layer_get_texture);
8065- lua_register(L, "layer_reset_effects", l_layer_reset_effects);
8066- lua_register(L, "layer_clear", l_layer_clear);
8067: lua_register(L, "layer_render", l_layer_render);
8068- lua_register(L, "layer_draw_from", l_layer_draw_from);
8069- \ --- Physics: World & Bodies ---
8070- lua_register(L, "physics_init", l_physics_init);
[Showing results with pagination = limit: 60, offset: 0]
Grep (engine_present|engine_frame|swap|SDL_GL_Swap)
405- int height;
406-
407- // Effect ping-pong buffers (created on first use)
408- GLuint effect_fbo;
409- GLuint effect_texture;
410: bool textures_swapped; // Which buffer is current result
411-
412- \ Transform stack (mat3 stored as 9 floats: row-major)
413- \ Each mat3: [m00 m01 m02 m10 m11 m12 m20 m21 m22]
414- // Represents 2D affine transform (2x3 used, bottom row is 0,0,1)
415- float transform_stack[MAX_TRANSFORM_DEPTH * 9];
--
1688- glBindTexture(GL_TEXTURE_2D, 0);
1689-}
1690-
1691-// Get the current result texture (accounts for ping-pong state)
1692-static GLuint layer_get_texture(Layer* layer) {
1693: return layer->textures_swapped ? layer->effect_texture : layer->color_texture;
1694-}
1695-
1696-// Reset effect state for start of frame (call after layer_flush, before new frame)
1697-static void layer_reset_effects(Layer* layer) {
1698: layer->textures_swapped = false;
1699-}
1700-
1701-// Get pointer to current transform (mat3 at current depth)
1702-static float* layer_get_transform(Layer* layer) {
1703- return &layer->transform_stack[layer->transform_depth * 9];
--
3538- // Ensure effect buffer exists
... [71 more lines]Now let me look at the main loop to understand frame timing:
Read (E:\a327ex\Anchor\engine\src\anchor.c)
9080→ int offset_y = (window_h - scaled_h) / 2;
9081→
9082→ // Clear screen to black (letterbox color)
9083→ glViewport(0, 0, window_w, window_h);
9084→ glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
9085→ glClear(GL_COLOR_BUFFER_BIT);
9086→
9087→ // Set viewport for game area
9088→ glViewport(offset_x, offset_y, scaled_w, scaled_h);
9089→ glUseProgram(screen_shader);
9090→
9091→ // Use premultiplied alpha blend for compositing layers to screen
9092→ // FBO contents are already blended, so we don't multiply by src alpha again
9093→ glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
9094→
9095→ // Get offset uniform location
9096→ GLint offset_loc = glGetUniformLocation(screen_shader, "u_offset");
9097→
9098→ if (layer_draw_count > 0) {
9099→ // Manual compositing: use layer_draw queue
9100→ for (int i = 0; i < layer_draw_count; i++) {
9101→ LayerDrawCommand* cmd = &layer_draw_queue[i];
9102→ Layer* layer = cmd->layer;
9103→
9104→ // Convert game coordinates to NDC offset
9105→ // Game coords: (0,0) top-left, positive Y down
9106→ // NDC: (-1,-1) bottom-left, positive Y up
9107→ // Offset in NDC = (game_offset / game_size) * 2
9108→ float ndc_x = (cmd->x / game_width) * 2.0f;
9109→ float ndc_y = -(cmd->y / game_height) * 2.0f; // Flip Y
... [50 more lines]Let me see the main loop structure more broadly — where the headless path diverges and how update/draw are called:
Read (E:\a327ex\Anchor\engine\src\anchor.c)
8990→ lua_pop(L, 2); // error + traceback
8991→ error_state = true;
8992→ } else {
8993→ lua_pop(L, 1); // traceback
8994→ }
8995→ } else {
8996→ lua_pop(L, 2); // nil + traceback
8997→ }
8998→ }
8999→
9000→ step++;
9001→ game_time += PHYSICS_RATE;
9002→ physics_lag -= PHYSICS_RATE;
9003→
9004→ // Copy current input state to previous for next frame's edge detection
9005→ input_post_update();
9006→ chords_post_update();
9007→ }
9008→
9009→ // Render at 60Hz (for chunky pixel movement on high-refresh monitors)
9010→ if (render_lag >= RENDER_RATE) {
9011→ render_lag -= RENDER_RATE;
9012→ frame++;
9013→ draw_calls = 0; // Reset draw call counter for this frame
9014→
9015→ // Calculate FPS from dt_history average
9016→ if (dt_history_filled) {
9017→ double avg_dt = 0;
9018→ for (int i = 0; i < DT_HISTORY_COUNT; i++) avg_dt += dt_history[i];
9019→ avg_dt /= DT_HISTORY_COUNT;
... [70 more lines]
Read (E:\a327ex\Anchor\engine\src\anchor.c)
9316→ if (!headless_mode) {
9317→ // Initialize vsync snap frequencies based on display refresh rate
9318→ int display_hz = 60; // Default fallback
9319→ SDL_DisplayMode mode;
9320→ if (SDL_GetCurrentDisplayMode(0, &mode) == 0 && mode.refresh_rate > 0) {
9321→ display_hz = mode.refresh_rate;
9322→ }
9323→ printf("Display refresh rate: %dHz\n", display_hz);
9324→
9325→ // Compute snap frequencies for this refresh rate and its multiples
9326→ // (handles 1x, 2x, 3x... of the base frame time for missed frames)
9327→ double base_frametime = 1.0 / (double)display_hz;
9328→ snap_frequency_count = 0;
9329→ for (int i = 1; i <= 8 && snap_frequency_count < 8; i++) {
9330→ snap_frequencies[snap_frequency_count++] = base_frametime * i;
9331→ }
9332→ }
9333→
9334→ #ifdef __EMSCRIPTEN__
9335→ // Use browser's requestAnimationFrame
9336→ // 0 = use RAF, 1 = simulate infinite loop (blocking)
9337→ emscripten_set_main_loop(main_loop_iteration, 0, 1);
9338→ #else
9339→ if (headless_mode) {
9340→ // Headless: tight update loop — no timing, no rendering, max speed
9341→ printf("Headless loop starting...\n");
9342→ lua_pushcfunction(L, traceback);
9343→ int err_handler = lua_gettop(L);
9344→ while (running && !error_state) {
9345→ // Clear layer commands (update code may call draw functions)
... [10 more lines]
Read (E:\a327ex\Anchor\engine\src\anchor.c)
9355→ physics_process_events();
9356→ }
9357→ // Call Lua update(dt)
9358→ lua_getglobal(L, "update");
9359→ if (lua_isfunction(L, -1)) {
9360→ lua_pushnumber(L, PHYSICS_RATE);
9361→ if (lua_pcall(L, 1, 0, err_handler) != LUA_OK) {
9362→ snprintf(error_message, sizeof(error_message), "%s", lua_tostring(L, -1));
9363→ fprintf(stderr, "ERROR: %s\n", error_message);
9364→ lua_pop(L, 1);
9365→ error_state = true;
9366→ }
9367→ } else {
9368→ lua_pop(L, 1);
9369→ }
9370→ step++;
9371→ game_time += PHYSICS_RATE;
9372→ // Post-update input state (needed for edge detection even if no real input)
9373→ input_post_update();
9374→ }
9375→ lua_pop(L, 1); // traceback
9376→ } else {
9377→ // Desktop: traditional blocking loop
9378→ while (running) {
9379→ main_loop_iteration();
9380→ }
9381→ }
9382→
9383→ printf("Shutting down...\n");
9384→ engine_shutdown();
... [9 more lines]Now I have a solid understanding of the architecture. Let me check one more thing — the sound_play_handle function to understand the full audio API:
Grep (sound_play_handle)
2120- @thrust_sound_start_pitch = an.random\float(0.7, 1.1)
2121- @thrust_sound_end_pitch = an.random\float(2.0, 2.8)
2122: @thrust_sound_handle = an\sound_play_handle 'wind_small_impact_1', 0.65, @thrust_sound_start_pitch
2123- @thrust_hit_this_thrust = false
2124- @thrust_progress = 0Okay. I now have a thorough understanding. Here are my questions:
AskUserQuestion (The current headless mode skips all rendering (no window, no OpenGL, no FBOs). F...)
User has answered your questions: "The current headless mode skips all rendering (no window, no OpenGL, no FBOs). For frame capture, we need actual rendering to happen. Two broad approaches:
**A) New "capture" mode** — Run the game normally with a window and OpenGL, but instead of displaying to screen, read back each frame's pixels via glReadPixels after the layer compositing step and save to PNG. The game would run at full speed (not real-time), stepping deterministically. This is simpler since all the rendering code already works.
**B) Offscreen rendering** — Create an OpenGL context without a visible window (or with a hidden window), render to an FBO at 480x270, and read back pixels. More elegant (no window flash) but requires ensuring SDL can create a hidden window with a valid GL context.
Which approach do you prefer?"="A: Visible window (Recommended)", "For sound logging: the game calls `an\sound_play` with name, volume, and pitch. We need to intercept these. Should I:
A) Add a C-level hook that logs every sound_play call to a Lua table when in capture mode
B) Wrap it in YueScript — replace/monkey-patch `an\sound_play` to both play (or not play) the sound AND log it
Option B is simpler and doesn't touch the engine. The logged data would be: {frame, sound_name, volume, pitch}. For the final video, we'd use ffmpeg to layer the actual .ogg sound files at the right timestamps with the right pitch/volume."="YueScript wrapper (Recommended)", "For the final video assembly with ffmpeg: a 120Hz physics step battle could produce thousands of frames. The game updates at 120Hz but renders at 60Hz. Should the capture save frames at 60fps (matching visual render rate) or 120fps (every physics step)?"="60fps (Recommended)", "How should this feature be invoked? The existing headless mode uses CLI args like `--headless --matchup=dagger,sword --seed=42`. I'm thinking a new mode like `--capture --matchup=dagger,sword --seed=42` that runs with rendering enabled, captures frames to a temp directory, then runs ffmpeg at the end. Does that work, or do you have a different invocation in mind?"="Yes, the flag, except I don't know if it should be called Capture Mode or something else, let's discuss this." user notes: Yes, the flag, except I don't know if it should be called Capture Mode or something else, let's discuss this.. You can now continue with the user's answers in mind.Good — all the technical choices are settled. On naming, here are some options:
AskUserQuestion (What should the mode/flag be called? Some options based on what it does (render ...)
User has answered your questions: "What should the mode/flag be called? Some options based on what it does (render a battle to video):"="--render". You can now continue with the user's answers in mind.--render it is. Let me plan the implementation.
EnterPlanMode
Entered plan mode. You should now focus on exploring the codebase and designing an implementation approach.
In plan mode, you should:
1. Thoroughly explore the codebase to understand existing patterns
2. Identify similar features and architectural approaches
3. Consider multiple approaches and their trade-offs
4. Use AskUserQuestion if you need to clarify the approach
5. Design a concrete implementation strategy
6. When ready, use ExitPlanMode to present your plan for approval
Remember: DO NOT write or edit any files yet. This is a read-only exploration and planning phase.I've already done extensive exploration of the codebase in the pre-plan conversation. Let me now look at a few remaining details I need for the plan — specifically around how the engine handles the main loop timing to understand how to make it step deterministically without vsync/timing constraints, and how to add a glReadPixels capture step.
Task (Explore render loop details)
[
{
"type": "text",
"text": "Perfect! Now I have comprehensive information. Let me compile the findings into a clear report for the user.\n\n## Engine Exploration Report: \"Render Mode\" Feature for PNG Frame Capture\n\nI've thoroughly explored the Anchor engine codebase and gathered all the specific details you need for planning a render mode feature. Here are the findings organized by your requested areas:\n\n---\n\n### 1. Main Loop Timing & Deterministic Stepping\n\n**File:** `E:/a327ex/Anchor/engine/src/anchor.c`\n\n**Key Constants (Lines 94-96):**\n```c\n#define PHYSICS_RATE (1.0 / 120.0) // 120 Hz physics/input timestep\n#define RENDER_RATE (1.0 / 60.0) // 60 Hz render cap (for chunky pixel movement)\n#define MAX_UPDATES 10 // Cap on fixed steps per frame (prevents spiral of death)\n```\n\n**Timing Variables (Lines 8228-8233):**\n```c\nstatic double physics_lag = 0.0;\nstatic double render_lag = 0.0;\nstatic Uint64 step = 0;\nstatic double game_time = 0.0;\nstatic Uint64 frame = 0;\n```\n\n**Main Loop Structure** (`main_loop_iteration()` at **line 8778**):\n- Reads real delta time from SDL performance counter (line 8779-8780)\n- Clamps and smooths delta time with VSync snapping and averaging (lines 8786-8827)\n- **Accumulates to `physics_lag` and `render_lag`** (lines 8830-8839)\n- **Fixed timestep loop:** `while (physics_lag >= PHYSICS_RATE)` advances one 120Hz physics step (line 8958)\n- **Fixed render check:** `if (render_lag >= RENDER_RATE)` triggers one 60Hz render frame (line 9010)\n\n**Desktop Main Loop** (lines 9376-9381):\n```c\n} else {\n // Desktop: traditional blocking loop\n while (running) {\n main_loop_iteration();\n }\n}\n```\n\n**Critical Insight for Deterministic Mode:** The engine **is already deterministic if you bypass the real-time delta time reading.** The accumulators `physics_lag` and `render_lag` control stepping. You could inject a fixed `dt` value (e.g., `1.0/60.0` per iteration) to make each iteration advance exactly one physics step + one render step. This would be much simpler than refactoring the entire loop.\n\n---\n\n### 2. CLI Argument Parsing\n\n**File:** `E:/a327ex/Anchor/engine/src/anchor.c`\n\n**CLI Argument Storage** (Lines 84-89):\n```c\n#define MAX_CLI_ARGS 32\n#define MAX_CLI_KEY 64\n#define MAX_CLI_VALUE 256\nstatic struct { char key[MAX_CLI_KEY]; char value[MAX_CLI_VALUE]; } cli_args[MAX_CLI_ARGS];\nstatic int cli_arg_count = 0;\n```\n\n**Parsing Logic** (Lines 9171-9208):\n- `--headless` flag sets `headless_mode = true` (line 9175-9177)\n- `--key=value` pairs are parsed and stored in `cli_args` array (lines 9178-9195)\n- Key extraction uses `strchr(arg, '=')` to split on `=` (line 9181)\n- If no `=`, defaults to value `\"true\"` (line 9193)\n\n**Lua Access** (`engine_get_args()` at **line 7815**):\n```c\nstatic int l_engine_get_args(lua_State* L) {\n lua_newtable(L);\n for (int i = 0; i < cli_arg_count; i++) {\n lua_pushstring(L, cli_args[i].value);\n lua_setfield(L, -2, cli_args[i].key); // table[key] = value\n }\n return 1;\n}\n```\n\n**How to use from YueScript:**\n```lua\nlocal args = engine_get_args()\nif args.render_mode then\n -- capture frames\nend\n```\n\n**Headless Mode Access** (Lines 7787-7803):\n```c\nstatic int l_engine_get_headless(lua_State* L) {\n lua_pushboolean(L, headless_mode);\n return 1;\n}\n```\n\n---\n\n### 3. Image Writing Capability (stb_image_write)\n\n**File:** `E:/a327ex/Anchor/engine/src/anchor.c`\n\n**Status: NOT INCLUDED**\n\nThe engine includes several stb libraries:\n- **Line 45-46:** `stb_image.h` (for loading)\n- **Line 48-49:** `stb_perlin.h` (for noise)\n- **Line 51-52:** `stb_vorbis.c` (for audio)\n\n**But NO `stb_image_write.h` is included.** This is a gap you'll need to fill. The good news: stb_image_write is a single-header library, so you can:\n1. Add `#define STB_IMAGE_WRITE_IMPLEMENTATION` before the include\n2. Include it at the top with the other stb headers\n3. Use `stbi_write_png(filename, width, height, channels, data, stride)` to write PNG files\n\nThe header should be added around **line 45-52** where the other stb includes live.\n\n---\n\n### 4. The `sound_play()` C Function Signature\n\n**File:** `E:/a327ex/Anchor/engine/src/anchor.c`, Lines 1293-1351\n\n```c\nstatic int sound_play(Sound* sound, float volume, float pitch) {\n // Returns: slot index (0+) or -1 if no free slots\n```\n\n**Full Implementation (1293-1351):**\n- Takes `Sound*` pointer, `volume` (0-1 perceptual), `pitch` (1.0 = normal)\n- Finds a free slot in `playing_sounds[]` array\n- Initializes miniaudio decoder and sound object\n- Applies volume: `linear_to_perceptual(volume * sound_master_volume)` (line 1342)\n- Applies pitch: `pitch * audio_master_pitch` (line 1345)\n- Marks slot as in-use and starts playback\n- **Returns**: slot index (int) or -1 on failure\n\n**Lua Binding** (Lines 4933-4939):\n```c\nstatic int l_sound_play(lua_State* L) {\n Sound* sound = (Sound*)lua_touserdata(L, 1);\n float volume = (float)luaL_optnumber(L, 2, 1.0);\n float pitch = (float)luaL_optnumber(L, 3, 1.0);\n sound_play(sound, volume, pitch);\n return 0; // Returns nothing to Lua\n}\n\nstatic int l_sound_play_handle(lua_State* L) {\n // Same as above but RETURNS the handle (encoded slot + generation)\n int slot = sound_play(sound, volume, pitch);\n lua_pushinteger(L, sound_handle_encode(slot, playing_sounds[slot].generation));\n return 1; // Returns handle to Lua\n}\n```\n\n**For a Monkey-Patch:** You'd need to intercept the Lua call and record when sounds are played. Since the C function doesn't return the slot to regular `sound_play()`, you'd use `sound_play_handle()` as the basis for your wrapper, or add a new engine function specifically for render mode.\n\n---\n\n### 5. Frame Capture Hook Point (glReadPixels)\n\n**File:** `E:/a327ex/Anchor/engine/src/anchor.c`\n\n**The Render Pipeline** (Lines 9041-9149):\n\n**PASS 1: Lua draw() executes (lines 9041-9060)**\n- Unbinds any active texture (line 9043)\n- Calls `lua_getglobal(L, \"draw\")` and executes it (lines 9046-9059)\n- At this point, all layers are rendered to their FBOs but nothing is composited to screen yet\n\n**PASS 2: Composite layers to screen (lines 9062-9149)**\n- `glBindFramebuffer(GL_FRAMEBUFFER, 0)` \u2014 **switches to default framebuffer** (line 9063)\n- Clears window to black (lines 9083-9085)\n- Sets up viewport and projection for game coordinates (lines 9087-9088)\n- Loops through `layer_draw_queue` (lines 9100-9118) or all layers (lines 9131-9142)\n- Each layer texture is bound and rendered as a full-screen quad (lines 9113-9117 or 9134-9138)\n- **After the compositing loop (line 9143), before `SDL_GL_SwapWindow()`** is the ideal hook point\n- `glBlendFuncSeparate` is reset to standard alpha blending (lines 9146-9147)\n- **`SDL_GL_SwapWindow(window)` swaps buffers (line 9149)**\n\n**Optimal Insertion Point for PNG Capture:**\n\nBetween **line 9143** (end of compositing) and **line 9149** (buffer swap):\n```c\n// After all compositing to FBO 0 (default framebuffer), before swap:\nif (should_capture_this_frame) {\n // At this point, FBO 0 (default framebuffer) contains the composited frame\n // glReadPixels reads from the currently bound read framebuffer\n glReadPixels(0, 0, game_width, game_height, GL_RGBA, GL_UNSIGNED_BYTE, pixel_buffer);\n // Write pixel_buffer to PNG via stbi_write_png()\n}\n\nSDL_GL_SwapWindow(window);\n```\n\n**Critical FBO State at This Point:**\n- `GL_FRAMEBUFFER` is **bound to 0** (the default/screen framebuffer) (line 9063)\n- All layer compositing has drawn to this framebuffer\n- The **viewport is set to the game area** within the window (line 9088: `game_width, game_height`)\n- You should read the **game_width \u00d7 game_height** region, not the full window\n\n**Layer Structure** (Lines 400-425):\n```c\ntypedef struct {\n GLuint fbo; // Main FBO\n GLuint color_texture; // Main color render target\n GLuint effect_fbo; // Effect/shader ping-pong\n GLuint effect_texture; // Effect target\n bool textures_swapped; // Which buffer is current\n // ... transform stack, command queue ...\n} Layer;\n```\n\n**Getting Texture from Layer** (Line 1692-1693):\n```c\nstatic GLuint layer_get_texture(Layer* layer) {\n return layer->textures_swapped ? layer->effect_texture : layer->color_texture;\n}\n```\n\nThis shows layers are FBO-based with dual-buffer effects support.\n\n---\n\n## Summary & Actionable Insights\n\n| Aspect | Finding |\n|--------|---------|\n| **Determinism** | Engine is already fixed-timestep; just inject fixed `dt` (~1/60s) to make it deterministic. Accumulators handle the rest. |\n| **CLI Args** | Accessible via `engine_get_args()` Lua function; returns table `{key = value}`. |\n| **Image Writing** | **Not included**; need to add `stb_image_write.h` header and link. |\n| **Sound Interception** | `sound_play()` returns slot index; need to wrap `sound_play_handle()` for render mode tracking. |\n| **Frame Capture** | Insert `glReadPixels()` between line 9143\u20139149 in `main_loop_iteration()`. FBO 0 is bound; viewport is correctly set to game area. |\n| **Pixel Format** | Read as `GL_RGBA` + `GL_UNSIGNED_BYTE` (4 bytes per pixel, standard). |\n\nThe engine is well-structured for this feature. The main work is adding stb_image_write and creating a deterministic mode with frame capture hooks."
},
{
"type": "text",
"text": "agentId: a006ef94d80cd5717 (for resuming to continue this agent's work if needed)\n<usage>total_tokens: 43569\ntool_uses: 22\nduration_ms: 87280</usage>"
}
]Excellent. Now let me look at one more critical detail — the viewport setup when reading pixels, because the compositing happens at a scaled viewport within the window, not at 480x270 directly:
Read (E:\a327ex\Anchor\engine\src\anchor.c)
9062→ // === PASS 2: Composite all layers to screen ===
9063→ glBindFramebuffer(GL_FRAMEBUFFER, 0);
9064→
9065→ // Get current window size
9066→ int window_w, window_h;
9067→ SDL_GetWindowSize(window, &window_w, &window_h);
9068→
9069→ // Calculate scale to fit window while maintaining aspect ratio
9070→ // Calculate scale to fit window while maintaining aspect ratio
9071→ float scale_x = (float)window_w / game_width;
9072→ float scale_y = (float)window_h / game_height;
9073→ float scale = (scale_x < scale_y) ? scale_x : scale_y;
9074→ if (scale < 1.0f) scale = 1.0f;
9075→
9076→ // Calculate centered position with letterboxing
9077→ int scaled_w = (int)(game_width * scale);
9078→ int scaled_h = (int)(game_height * scale);
9079→ int offset_x = (window_w - scaled_w) / 2;
9080→ int offset_y = (window_h - scaled_h) / 2;
9081→
9082→ // Clear screen to black (letterbox color)
9083→ glViewport(0, 0, window_w, window_h);
9084→ glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
9085→ glClear(GL_COLOR_BUFFER_BIT);
9086→
9087→ // Set viewport for game area
9088→ glViewport(offset_x, offset_y, scaled_w, scaled_h);
9089→ glUseProgram(screen_shader);
9090→
9091→ // Use premultiplied alpha blend for compositing layers to screenI see — the compositing is done at the scaled viewport (e.g., 480x270 * 3 = 1440x810), not at the native 480x270. For frame capture we'd want to read the pixels from the layer FBOs directly at their native 480x270 resolution, or read from the default framebuffer at the scaled region.
Actually, the cleaner approach is to render to a dedicated capture FBO at 480x270 instead of reading from the default framebuffer. But let me check if we can just use glReadPixels on the game area of the default framebuffer. The issue is the layers are composited at the scaled size, so reading at that region would give us scaled_w x scaled_h pixels — which would be 1440x810 at scale=3. We want 480x270 native.
Better approach: create a dedicated capture FBO at 480x270, composite layers to that instead of (or in addition to) the default framebuffer, then read pixels from there. Or, since the layer FBOs are already at 480x270, we can composite them to a capture FBO at native resolution.
Let me check how layers are created to confirm their resolution:
Grep (layer_create|Layer* layer.*malloc)
1574- }
1575-}
1576-#endif
1577-
1578-// ============================================================================
1579-// LAYER SYSTEM
1580-// FBO management, transform stack, command queue, drawing primitives
1581-// ============================================================================
1582-
1583-// Create a layer with FBO at specified resolution
1584:static Layer* layer_create(int width, int height) {
1585- Layer* layer = (Layer*)calloc(1, sizeof(Layer));
1586- if (!layer) return NULL;
1587-
1588- layer->width = width;
1589- layer->height = height;
1590-
1591- // Initialize transform stack with identity matrix at depth 0
1592- layer->transform_depth = 0;
1593- float* m = layer->transform_stack;
1594- m[0] = 1.0f; m[1] = 0.0f; m[2] = 0.0f; // row 0
--
4403- return layer_registry[i];
4404- }
4405- }
4406-
4407- // Create new layer
4408- if (layer_count >= MAX_LAYERS) {
4409- fprintf(stderr, "Error: Maximum number of layers (%d) reached\n", MAX_LAYERS);
4410- return NULL;
... [57 more lines]Good — layers are created at game_width x game_height (480x270). So the layer FBOs are already at native resolution. The compositing to screen just happens at a scaled viewport. For frame capture, the cleanest approach is:
- Create a dedicated capture FBO at 480x270
- After the normal draw() call, composite layers to this capture FBO (same as the screen compositing but at native resolution)
glReadPixelsfrom the capture FBO- Write to PNG
This avoids reading from the scaled default framebuffer entirely.
Now let me also think about the timing. For render mode, we don't want real-time — we want to step the simulation deterministically and capture every render frame. The key is controlling physics_lag and render_lag. If we inject exactly RENDER_RATE (1/60) as the delta time each iteration, then each iteration will do 2 physics steps (120Hz/60Hz = 2) and 1 render.
Let me now check one more thing — how to make the engine not use real-time timing:
Read (E:\a327ex\Anchor\engine\src\anchor.c)
8778→static void main_loop_iteration(void) {
8779→ Uint64 current_time = SDL_GetPerformanceCounter();
8780→ double dt = (double)(current_time - last_time) / (double)perf_freq;
8781→ last_time = current_time;
8782→
8783→ // Clean up finished sounds (must be done from main thread)
8784→ sound_cleanup_finished();
8785→
8786→ // Clamp delta time to handle anomalies (pauses, debugger, sleep resume)
8787→ if (dt > PHYSICS_RATE * MAX_UPDATES) {
8788→ dt = PHYSICS_RATE;
8789→ }
8790→ if (dt < 0) {
8791→ dt = 0;
8792→ }
8793→
8794→ // VSync snapping: if dt is close to a known refresh rate, snap to it exactly
8795→ // This prevents accumulator drift from timer jitter
8796→ for (int i = 0; i < snap_frequency_count; i++) {
8797→ double diff = dt - snap_frequencies[i];
8798→ if (diff < 0) diff = -diff;
8799→ if (diff < VSYNC_SNAP_TOLERANCE) {
8800→ dt = snap_frequencies[i];
8801→ break;
8802→ }
8803→ }
8804→
8805→ // Delta time averaging: smooth out OS scheduling jitter
8806→ // A single slow frame gets spread across multiple frames instead of spiking
8807→ dt_history[dt_history_index] = dt;
... [40 more lines]Now I have a complete picture. For render mode, the simplest approach is to add a new loop (similar to headless) that's like the normal loop but without timing — force-inject RENDER_RATE each iteration so it always steps 2 physics + 1 render per iteration, capturing the frame after compositing.
Let me also check if there are stb_image_write headers already available nearby:
Glob (*/stb_image_write)
No files found
Read (E:\a327ex\Anchor\engine\src\anchor.c)
40→
41→#include <lua.h>
42→#include <lualib.h>
43→#include <lauxlib.h>
44→
45→#define STB_IMAGE_IMPLEMENTATION
46→#include <stb_image.h>
47→
48→#define STB_PERLIN_IMPLEMENTATION
49→#include <stb_perlin.h>
50→
51→#define STB_VORBIS_HEADER_ONLY
52→#include <stb_vorbis.c>
53→
54→#include <ft2build.h>
55→#include <freetype/freetype.h>
56→
57→#define MA_ENABLE_VORBIS
58→#define MINIAUDIO_IMPLEMENTATION
59→#include <miniaudio.h>No stb_image_write.h in the project. We'll need to download it. Let me check the include path to know where to put it:
Glob (**/stb_image.h)
E:\a327ex\Anchor\engine\include\stb\stb_image.hGood — stb headers live in Anchor/engine/include/stb/. We'll put stb_image_write.h there.
Now let me check the build system to see if we need to update anything:
Read (E:\a327ex\Anchor\engine\build.bat)
1→@echo off
2→setlocal
3→
4→cd /d "%~dp0"
5→
6→:: Find and run vcvarsall.bat for Visual Studio
7→if exist "C:\Program Files\Microsoft Visual Studio\18\Community\VC\Auxiliary\Build\vcvarsall.bat" (
8→ call "C:\Program Files\Microsoft Visual Studio\18\Community\VC\Auxiliary\Build\vcvarsall.bat" x64 >nul 2>&1
9→) else if exist "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsall.bat" (
10→ call "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvarsall.bat" x64 >nul 2>&1
11→) else if exist "C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Auxiliary\Build\vcvarsall.bat" (
12→ call "C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Auxiliary\Build\vcvarsall.bat" x64 >nul 2>&1
13→) else if exist "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" (
14→ call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" x64 >nul 2>&1
15→) else (
16→ echo ERROR: Could not find Visual Studio
17→ exit /b 1
18→)
19→
20→if not exist build mkdir build
21→
22→:: Build Lua library if it doesn't exist
23→if not exist lib\lua.lib (
24→ echo Building Lua library...
25→ if not exist build\lua_obj mkdir build\lua_obj
26→ cl.exe /nologo /O2 /W3 /c /I"include/lua" ^
27→ include/lua/lapi.c include/lua/lauxlib.c include/lua/lbaselib.c ^
28→ include/lua/lcode.c include/lua/lcorolib.c include/lua/lctype.c ^
29→ include/lua/ldblib.c include/lua/ldebug.c include/lua/ldo.c ^
30→ include/lua/ldump.c include/lua/lfunc.c include/lua/lgc.c ^
... [76 more lines]The include path already has /I"include/stb", so we just need to drop stb_image_write.h into Anchor/engine/include/stb/ and include it in anchor.c. No build changes needed.
Now let me check how the framework wraps sound_play to understand what we'd monkey-patch:
Grep (sound_play)
E:\a327ex\Anchor\framework\anchor\init.lua-243-
E:\a327ex\Anchor\framework\anchor\init.lua-244-
E:\a327ex\Anchor\framework\anchor\init.lua-245-
E:\a327ex\Anchor\framework\anchor\init.lua-246-
E:\a327ex\Anchor\framework\anchor\init.lua-247-
E:\a327ex\Anchor\framework\anchor\init.lua:248:an.sound_play = function(self, name, volume, pitch)if volume == nil then volume = 1 end;if pitch == nil then pitch = 1 end;return
E:\a327ex\Anchor\framework\anchor\init.lua:249:sound_play(self.sounds[name], volume, pitch)end
E:\a327ex\Anchor\framework\anchor\init.lua-250-
E:\a327ex\Anchor\framework\anchor\init.lua:251:an.sound_play_handle = function(self, name, volume, pitch)if volume == nil then volume = 1 end;if pitch == nil then pitch = 1 end;return
E:\a327ex\Anchor\framework\anchor\init.lua:252:sound_play_handle(self.sounds[name], volume, pitch)end
E:\a327ex\Anchor\framework\anchor\init.lua-253-
E:\a327ex\Anchor\framework\anchor\init.lua-254-an.sound_handle_set_pitch = function(self, handle, pitch)return
E:\a327ex\Anchor\framework\anchor\init.lua-255-sound_handle_set_pitch(handle, pitch)end
E:\a327ex\Anchor\framework\anchor\init.lua-256-
E:\a327ex\Anchor\framework\anchor\init.lua-257-an.sound_handle_set_volume = function(self, handle, volume)return
--
E:\a327ex\Anchor\framework\anchor\init.yue-234-
E:\a327ex\Anchor\framework\anchor\init.yue-235- --[[
E:\a327ex\Anchor\framework\anchor\init.yue-236- Plays a sound effect by name.
E:\a327ex\Anchor\framework\anchor\init.yue-237-
E:\a327ex\Anchor\framework\anchor\init.yue-238- Usage:
E:\a327ex\Anchor\framework\anchor\init.yue:239: an\sound_play 'hit'
E:\a327ex\Anchor\framework\anchor\init.yue:240: an\sound_play 'hit', 0.5 -- half volume
E:\a327ex\Anchor\framework\anchor\init.yue:241: an\sound_play 'hit', 1, 1.2 -- normal volume, higher pitch
E:\a327ex\Anchor\framework\anchor\init.yue-242-
E:\a327ex\Anchor\framework\anchor\init.yue-243- Parameters:
E:\a327ex\Anchor\framework\anchor\init.yue-244- name - sound name (registered via an\sound)
E:\a327ex\Anchor\framework\anchor\init.yue-245- volume - (optional) volume 0-1, default 1
E:\a327ex\Anchor\framework\anchor\init.yue-246- pitch - (optional) pitch multiplier, default 1
E:\a327ex\Anchor\framework\anchor\init.yue-247- ]]
... [10 more lines]Good — an.sound_play is a method on the an table that takes name, volume, pitch. Easy to monkey-patch in the game's YueScript.
Now let me also understand where the framework checks an.headless and an.args, so we know how to add an.render_mode:
Grep (an.headless|an.args)
No matches found
Grep (headless|get_args)
No matches found
Grep (headless|get_args)
No matches found
Grep (an.headless|an.args)
4374-
4375--- headless: simulation runner (replaces normal arena creation)
4376:if an.headless
4377: headless_battles = tonumber(an.args.battles) or 1
4378: headless_matchup = an.args.matchup or 'dagger,sword'
4379- headless_weapon_a, headless_weapon_b = headless_matchup\match('(%w+),(%w+)')
4380: headless_base_seed = tonumber(an.args.seed) or 1
4381-
4382- os.execute "mkdir results 2>nul"
4383-
4384: if an.args.report
4385- -- Report-only mode: regenerate HTML from existing .dat file
4386- timestamp = os.date '%Y-%m-%d_%H%M%S'
--
4393- engine_quit!
4394-
4395: elseif an.args.balance
4396- -- Balance mode: run all weapon matchups and generate unified report
4397: headless_parallel = tonumber(an.args.parallel) or 8
4398: headless_filter = an.args.weapon
[Showing results with pagination = limit: 20, offset: 0]So an.headless and an.args are set somewhere — likely in the framework's compiled init. Let me check:
Grep (.headless|.args)
No matches found
[Showing results with pagination = limit: 20, offset: 0]
Grep (headless)
No matches found
Grep (engine_get_headless|engine_get_args)
E:\a327ex\Anchor\engine\src\anchor.c-7807- return 0;
E:\a327ex\Anchor\engine\src\anchor.c-7808-}
E:\a327ex\Anchor\engine\src\anchor.c-7809-
E:\a327ex\Anchor\engine\src\anchor.c:7810:static int l_engine_get_headless(lua_State* L) {
E:\a327ex\Anchor\engine\src\anchor.c-7811- lua_pushboolean(L, headless_mode);
E:\a327ex\Anchor\engine\src\anchor.c-7812- return 1;
E:\a327ex\Anchor\engine\src\anchor.c-7813-}
E:\a327ex\Anchor\engine\src\anchor.c-7814-
E:\a327ex\Anchor\engine\src\anchor.c:7815:static int l_engine_get_args(lua_State* L) {
E:\a327ex\Anchor\engine\src\anchor.c-7816- lua_newtable(L);
E:\a327ex\Anchor\engine\src\anchor.c-7817- for (int i = 0; i < cli_arg_count; i++) {
E:\a327ex\Anchor\engine\src\anchor.c-7818- lua_pushstring(L, cli_args[i].value);
--
E:\a327ex\Anchor\engine\src\anchor.c-8216- lua_register(L, "engine_set_fullscreen", l_engine_set_fullscreen);
E:\a327ex\Anchor\engine\src\anchor.c-8217- lua_register(L, "engine_set_resizable", l_engine_set_resizable);
E:\a327ex\Anchor\engine\src\anchor.c-8218- lua_register(L, "engine_set_headless", l_engine_set_headless);
E:\a327ex\Anchor\engine\src\anchor.c:8219: lua_register(L, "engine_get_headless", l_engine_get_headless);
E:\a327ex\Anchor\engine\src\anchor.c:8220: lua_register(L, "engine_get_args", l_engine_get_args);
E:\a327ex\Anchor\engine\src\anchor.c-8221- lua_register(L, "engine_quit", l_engine_quit);
E:\a327ex\Anchor\engine\src\anchor.c-8222- lua_register(L, "engine_init", l_engine_init);
E:\a327ex\Anchor\engine\src\anchor.c-8223-}
Grep (engine_get_headless|engine_get_args)
No matches foundThe an.headless and an.args must be set in the game's main.yue itself. Let me check:
Grep (an.headless\s=|an.args\s=)
No matches found
Grep (an.headless|an.args)
No matches found
Grep (headless|args)
No matches found
[Showing results with pagination = limit: 20, offset: 0]
Grep (engine_get_headless|engine_get_args)
Found 5 files
emoji-ball-battles\anchor\init.lua
Anchor\engine\src\anchor.c
anchor.blot.im\logs\ebb-headless-mode.md
emoji-ball-battles\anchor\init.yue
emoji-ball-battles\reference\headless-playthrough-plan.mdThe game has its own copy of the framework. Let me check:
Grep (engine_get_headless|engine_get_args)
90- -- Engine state: static values (don't change during runtime)
91- an.width = engine_get_width!
92- an.height = engine_get_height!
93- an.unscaled_dt = engine_get_unscaled_dt!
94- an.platform = engine_get_platform!
95: an.headless = engine_get_headless!
96: an.args = engine_get_args!
97-
98- -- Time scale state
99- an.time_scale = 1.0 -- Current time scale multiplier
100- an.dt = an.unscaled_dt -- Scaled dt (updated each frame)
101- an.hit_stop_active = false -- True during hitstopFound it — the game has its own framework copy at emoji-ball-battles/anchor/init.yue. an.headless and an.args are set at framework init from C functions. For render mode, we don't use --headless (we need full rendering), so an.headless will be false. We'll check an.args.render instead.
Now I have everything I need. Let me write the plan.
Write (C:\Users\adn.claude\plans\sorted-leaping-shamir.md)
File created successfully at: C:\Users\adn\.claude\plans\sorted-leaping-shamir.mdNow let me check how an.frame gets updated in the framework, since that's critical for sound-to-frame synchronization:
Grep (an.frame|an.step)
1487- ]]
1488- update = (dt) ->
1489- -- Update engine state: dynamic values
1490: an.frame = engine_get_frame!
1491: an.step = engine_get_step!
1492- an.time = engine_get_time!
1493- an.window_width, an.window_height = engine_get_window_size!
1494- an.scale = engine_get_scale!an.frame is updated at the start of each update() call from the C engine's frame counter. But in render mode, frame is only incremented once per render (after the 2 physics steps). During the 2 physics steps, an.frame will be the same value for both update() calls — but an.step will differ. This is actually perfect for our sound logging: sounds from both physics steps of the same render frame will correctly have the same frame number.
Wait — actually, an.frame is read from engine_get_frame() which reads the C frame variable. In the render mode loop, frame++ happens before the render, but after the 2 physics steps. So during the physics steps, frame hasn't been incremented yet for this iteration. Sounds during those 2 steps will see the previous frame's an.frame value.
Let me verify by looking at the C loop more carefully:
Read (E:\a327ex\Anchor\engine\src\anchor.c)
8955→ gamepad_update();
8956→
8957→ // Fixed timestep physics/input loop (120Hz)
8958→ while (physics_lag >= PHYSICS_RATE) {
8959→ // Clear commands on all layers at start of update
8960→ for (int i = 0; i < layer_count; i++) {
8961→ layer_clear_commands(layer_registry[i]);
8962→ }
8963→
8964→ // Update sequences (clear just_fired from last frame, check timeouts)
8965→ sequences_update((float)game_time);
8966→
8967→ // Check which actions were pressed and notify sequences
8968→ sequences_check_actions((float)game_time);
8969→
8970→ // Update holds (track how long actions have been held)
8971→ holds_update((float)PHYSICS_RATE);
8972→
8973→ // Step physics world (uses time_scale, so 0 during hitstop)
8974→ if (physics_initialized && physics_enabled) {
8975→ physics_clear_events(); // Clear event buffers before step
8976→ b2World_Step(physics_world, (float)(PHYSICS_RATE * time_scale), 4); // 4 sub-steps recommended
8977→ physics_process_events(); // Buffer events for Lua queries
8978→ }
8979→
8980→ // Call Lua update (skip if in error state)
8981→ if (!error_state) {
8982→ lua_pushcfunction(L, traceback);
8983→ int err_handler = lua_gettop(L);
8984→ lua_getglobal(L, "update");
... [30 more lines]I see: in the normal loop, frame++ happens before draw() but after all the physics steps. So an.frame in update() shows the previous frame's number. Draw commands from update() are for the frame that will be rendered when frame has been incremented.
For our render mode loop, the same pattern applies. The key is: sounds happen during update(), and the frame value at that point identifies which render frame they'll appear in. We should increment frame before the physics steps (or use frame+1 in sound logging).
Actually, looking more carefully: an.frame = engine_get_frame! is called at the start of each update(). In the normal loop, physics steps happen before frame++. So during both update calls, an.frame = old frame number. Then frame++ happens, then draw(). So sounds in update() for frame N are associated with render frame N+1 (the one that's about to be drawn). This is consistent — we just need to account for this offset in the sound log (subtract 1, or adjust the mapping when building audio).
Actually, the simplest approach: in the render mode loop, increment frame before the physics steps, so an.frame during update matches the frame being captured. This is a minor change to the render loop ordering.
Let me now refine and finalize the plan:
Write (C:\Users\adn.claude\plans\sorted-leaping-shamir.md)
The file C:\Users\adn\.claude\plans\sorted-leaping-shamir.md has been updated successfully.
ExitPlanMode ({"allowedPrompts": [{"tool": "Bash", "prompt": "build engine with build.bat"}, {"tool": "Bash", "prompt": "download s...)
The user doesn't want to proceed with this tool use. The tool use was rejected (eg. if it was a file edit, the new_string was NOT written to the file). To tell you how to proceed, the user said:
How are you capturing sound logs?Good question. The plan monkey-patches an.sound_play in YueScript — replacing it with a wrapper that logs {frame, sound_name, volume, pitch} to a table instead of actually playing the sound. Here's the specific mechanism:
At the start of render mode in main.yue:
render_sound_log = {}
original_sound_play = an.sound_play
an.sound_play = (name, volume=1, pitch=1) =>
render_sound_log[] = {frame: an.frame, sound: name, :volume, :pitch}
-- Don't call original — silent capture
Every call to an\sound_play 'hit', 0.5, 1.2 throughout the game code gets intercepted. Instead of playing audio through miniaudio, it appends {frame: 42, sound: 'hit', volume: 0.5, pitch: 1.2} to the render_sound_log table.
When the battle ends, the log is written to sounds.txt — one line per event:
42 hit 0.5 1.2
43 sword_swing_1 0.7 0.98
Then the ffmpeg audio assembly function reads this log and for each entry:
- Takes the corresponding
assets/{sound_name}.oggas an ffmpeg input - Applies pitch via
asetrate(resamples to change playback speed) - Applies volume via
volumefilter - Delays to the correct timestamp via
adelay(frame / 60fps * 1000 = milliseconds) - Mixes all streams together into a single
audio.wav
There's one thing I'm not covering though — sound_play_handle (used by the thrust weapon, line 2122). That function returns a handle used to later modify pitch/volume dynamically. The monkey-patch only covers sound_play.
AskUserQuestion (The thrust weapon uses an\sound_play_handle which returns a handle, then later...)
User has answered your questions: "The thrust weapon uses `an\sound_play_handle` which returns a handle, then later calls `sound_handle_set_pitch` to dynamically change the pitch over time. This is harder to capture in a sound log since the pitch changes frame-by-frame. Should we:
A) Log the initial play and ignore dynamic pitch changes (acceptable approximation — it's one weapon's thrust sound)
B) Also monkey-patch `sound_handle_set_pitch` and `sound_handle_set_volume` to track changes, then generate a more complex ffmpeg filter that changes pitch over time
C) Skip the monkey-patch approach and do sound capture at the C level instead"="Track handle changes too". You can now continue with the user's answers in mind.Got it — we'll track handle changes too. Let me think through the mechanism:
For sound_play_handle, we return a fake handle (just an incrementing ID), and store the association. Then sound_handle_set_pitch(handle, pitch) and sound_handle_set_volume(handle, volume) log pitch/volume changes per frame against that handle.
The sound log then has two types of entries:
- play:
{type: 'play', frame, sound, volume, pitch, handle} - set_pitch:
{type: 'set_pitch', frame, handle, pitch} - set_volume:
{type: 'set_volume', frame, handle, volume}
For ffmpeg, a handle-based sound with dynamic pitch becomes a series of short audio segments at different pitches, concatenated together. This is complex but doable.
Let me also check if there's a sound_handle_stop we need to handle:
Grep (sound_handle)
253- an.sound_play_handle = (name, volume=1, pitch=1) =>
254- sound_play_handle @sounds[name], volume, pitch
255-
256: an.sound_handle_set_pitch = (handle, pitch) =>
257: sound_handle_set_pitch handle, pitch
258-
259: an.sound_handle_set_volume = (handle, volume) =>
260: sound_handle_set_volume handle, volume
261-
262- --[[
263- Sets the master volume for all sound effects.
Grep (sound_handle)
1755- @thrust_progress = math.min(1, @thrust_progress + dt/@thrust_duration)
1756- speed = math.lerp(math.quad_out(@thrust_progress), @thrust_start_speed, @thrust_end_speed)
1757- @collider\set_velocity speed*math.cos(@thrust_angle), speed*math.sin(@thrust_angle)
1758: if @thrust_sound_handle
1759- t = @thrust_progress
1760- sp = @thrust_sound_start_pitch
1761- ep = @thrust_sound_end_pitch
1762- if t < 0.75
1763: an\sound_handle_set_pitch @thrust_sound_handle, sp + (ep - sp)*t/0.75
1764- else
1765- et = (t - 0.75)/0.25
1766: an\sound_handle_set_pitch @thrust_sound_handle, ep + ep*(math.exp(et*2) - 1)/(math.exp(2) - 1)
1767- elseif @weapon_type == 'bow'
1768- -- Auto-pull bow when cooldown reaches 75%
1769- bow_should_pull = @cooldown_bar.progress >= 0.75
--
2119- @thrusting = true
2120- @thrust_sound_start_pitch = an.random\float(0.7, 1.1)
2121- @thrust_sound_end_pitch = an.random\float(2.0, 2.8)
2122: @thrust_sound_handle = an\sound_play_handle 'wind_small_impact_1', 0.65, @thrust_sound_start_pitch
2123- @thrust_hit_this_thrust = false
2124- @thrust_progress = 0
2125- vx, vy = @collider\get_velocity!Good — it's used in exactly one place: the thrust weapon. sound_play_handle returns a handle, then sound_handle_set_pitch is called every physics step to ramp the pitch up from ~0.7 to ~2.8 over the thrust duration.
For the ffmpeg side, handling this properly means splitting the sound into segments at different pitches. But there's a much simpler approach that would work well: since we know the full pitch curve at the end (all the set_pitch log entries), we can generate the audio for a handle-based sound by:
- Computing the average pitch, or
- Generating a single pitch-varying audio file using sox or ffmpeg filters
Actually, the simplest correct approach: for handle-based sounds, we just record the complete pitch timeline, then in ffmpeg, use rubberband or just split into short segments with constant pitch. Given that this is a short wind sound (~0.5s), even just using the average pitch would sound close enough.
But since you said track all changes, let me update the plan with the full approach. Let me update the plan:
Write (C:\Users\adn.claude\plans\sorted-leaping-shamir.md)
The file C:\Users\adn\.claude\plans\sorted-leaping-shamir.md has been updated successfully.
ExitPlanMode ({"allowedPrompts": [{"tool": "Bash", "prompt": "build engine with build.bat"}, {"tool": "Bash", "prompt": "download s...)
The user doesn't want to proceed with this tool use. The tool use was rejected (eg. if it was a file edit, the new_string was NOT written to the file). To tell you how to proceed, the user said:
For the pitch sounds, isn't it easier to just create a sound file for that specific pitch progression instead of doing multiple segments? Like, take the original, modify it with ffmpeg with the pitch progression (whatever it happens to be), that's a new file. Do this for every different pitch progression in the battle, then just use those new ogg files directly.Yes, that's much cleaner. For each handle-based sound:
- Take the original
.oggfile - Apply the pitch curve as a single ffmpeg filter that changes pitch over time → write to a new
.oggin the render dir - Treat that new file as a simple one-shot sound with the correct start time, volume=original, pitch=1 (pitch already baked in)
The ffmpeg asetrate filter can't vary over time, but rubberband or atempo can't either in a single pass. However, we can use ffmpeg's aresample with a varying rate, or more practically: sox has a speed effect that can be applied with a "tempo map."
Actually, the simplest correct approach: since we have the full pitch timeline (e.g., pitch at every physics step), we can generate the waveform programmatically:
- Decode the original .ogg to raw samples (via ffmpeg)
- In Lua: resample/time-stretch according to the pitch curve — for each output sample, advance the read position by
pitch_at_timesamples. This is essentially variable-speed playback, which is just sample interpolation. - Write the result as a .wav
But writing a resampler in Lua is overkill. Simpler:
Piecewise constant approximation: Split the sound into N chunks (e.g., 5-10), each with a constant pitch (average pitch over that chunk's time span). Concatenate the pitch-shifted chunks into one file. With 10 chunks over a 0.5s sound, each chunk is 50ms — the pitch transitions will be inaudible.
ffmpeg -y -i original.ogg \
-filter_complex "
[0]atrim=0:0.05,asetrate=44100*0.9,aresample=44100[c0];
[0]atrim=0.05:0.10,asetrate=44100*1.1,aresample=44100[c1];
...
[c0][c1]...[cN]concat=n=N:v=0:a=1[out]
" -map "[out]" output.ogg
This is straightforward and each handle-based sound becomes one ffmpeg call producing one file, which then gets treated as a normal one-shot in the final mix.
AskUserQuestion (Does this piecewise approach work for you? Split the handle-based sound into ~10...)
User has answered your questions: "Does this piecewise approach work for you? Split the handle-based sound into ~10 time chunks, apply constant pitch per chunk, concatenate into a single new file. Then use that file as a simple one-shot in the final audio mix. The transitions between chunks would be imperceptible at 50ms granularity."="Piecewise chunks (Recommended)". You can now continue with the user's answers in mind.Let me update the plan with the finalized audio approach and submit for approval.
Edit (C:\Users\adn.claude\plans\sorted-leaping-shamir.md)
The file C:\Users\adn\.claude\plans\sorted-leaping-shamir.md has been updated successfully.
ExitPlanMode ({"allowedPrompts": [{"tool": "Bash", "prompt": "build engine with build.bat"}, {"tool": "Bash", "prompt": "download s...)
The user doesn't want to proceed with this tool use. The tool use was rejected (eg. if it was a file edit, the new_string was NOT written to the file). STOP what you are doing and wait for the user to tell you how to proceed.[Request interrupted by user for tool use]