cdak (webgl port)

A JavaScript / WebGL2 / WebAudio port of cdak by quite & orange (4k intro, Chaos Constructions 2010 — shader: unc, audio: brothomstates, code: ized), reconstructed by disassembling the 4 KB executables.

Two releases exist and both are ported:

• party (cdak_1024x768.exe, the compo version) — the default.
• final (cdak_final_*.exe, 19 Sep 2010) — the well known bright blue/white version, 252 s; different synth, different scene/tone mapping. #final.

Files:

file	what
index.html	launcher (version picker over a live frame of the intro) · space pauses · ← / → skip 5 s (jumping ahead of what the synth has generated waits for it) · f fullscreen · esc stops and returns to it
cdak.js	the pixel shaders of both versions (HLSL → GLSL ES 3.00), WebGL2 two-pass renderer, worker-based audio streaming
cdak_synth_final.js	the final's software synth, transliterated from the x87 code; bit-exact with the original
cdak_synth.js	the party version's synth; bit-exact with the original
h_table_final.js, h_table.js	optional: precomputed shader constants every 0.1 s, used for the launcher's background frame and ?t= debugging; imported on demand, only for the selected version

Version: the dropdown on the start screen, or #final / #party in the URL. Other URL parameters: ?w=1024&h=768 fixed render size (letterboxed), ?dpr=2 render at device pixels, ?t=120 render one frame at that time without audio. The sources are ES modules, so the page has to be served over http(s) — python3 -m http.server in this directory, then http://localhost:8000/ — rather than opened from file://. Needs WebGL2 with EXT_color_buffer_float (falls back to an 8-bit render target otherwise).

How the originals work

The executables are packed with Crinkler 1.2. The PE header doubles as the decompressor stub and as the table of import hashes (Crinkler 1.x stores each import's name hash in the dwords of the header; header fields that are forced by the PE format become unused IAT slots). The stub decompresses ~8 KB of code+data to 0x420000 and returns into an import loader that walks the PEB for kernel32 and resolves everything by rol 6 / xor name hash:

• kernel32: CreateThread ExitProcess LoadLibraryA Sleep (+lstrlenA party, SuspendThread ResumeThread final)
• user32: CreateWindowExA GetAsyncKeyState (+SetFocus ShowWindow party, ShowCursor final)
• d3d9: Direct3DCreate9 — d3dx9_37: D3DXCompileShader
• winmm: waveOutOpen waveOutPrepareHeader waveOutWrite waveOutGetPosition

Main thread: CreateWindowExA("edit", WS_POPUP|WS_VISIBLE, 1024×768), Direct3DCreate9(32), full-screen CreateDevice (X8R8G8B8, vsync), compiles one HLSL source twice with D3DXCompileShader(..., "p0"/"p1", "ps_3_0"), creates an A16B16G16R16F 1024×768 render-target texture (linear filtering, wrap), SetFVF(D3DFVF_XYZRHW), fills a 65536-entry noise table with an LCG, opens a 44.1 kHz 16-bit stereo waveOut with one looping buffer (party: 4 chunks of 2000 frames; final: 8 chunks of 1024 frames) and starts the synth thread. Per frame: shader constants (c0 = resolution, c1 = h = (level, t, ..); final adds c2 = m camera rotation, c3 = q camera position/fov, copied from the synth thread while it is suspended), pass 0 draws one big XYZRHW triangle with p0 into the float texture, pass 1 draws it with p1 into the back buffer, Present, GetAsyncKeyState(VK_ESCAPE). The final exits by itself at t = 252 s; the party version runs until ESC (the port returns to the launcher at 300 s, when its soundtrack has died out).

Synth thread: polls waveOutGetPosition and refills the chunk that just finished playing.

• party: 16 voices, each a Hann-windowed note whose length is random (11-octave fractal noise over the LCG table, lacunarity φ); when a voice's envelope wraps it re-triggers and advances a shared sequencer (52-step delta pattern, modulus 24→36→…→84→48→…, pitch lerped from random to the pattern over the first 29 s). 4 oscillators per voice with phase modulation, self- and cross-voice feedback, soft clipping; a 22-tap delay network with slow triangle modulation and band-pass feedback; voices fade out at 240–260 s.
• final: 31 additive automation segments (A[i] += a + (b-a)·smoothstep(t0,t1,t)^e) evaluated every 32 samples drive everything (note lengths, pitch-lerp, levels, delay feed, camera scale); 32 voices built from 6 "oscStep" units (phase accumulator with wrap flag, pulse/cosine shape, tanh Padé approximant x(27+x²)/(27+9x²)), Catmull-Rom interpolated noise for the per-voice parameters (updated every 32 samples), a 180-step delta pattern limited to its first 4 entries until 98 s, FM with an integer modulator ratio, a 24-tap modulated delay with band-pass feedback. The camera (m,q) is 8 noise-driven values scaled by automation.

Port notes

• The synths mirror the x87 code instruction for instruction: every fstp dword is a Math.fround, every fistp rounds half-to-even, the exact float32 constants are used (the final's constants have 16-bit mantissas — e.g. 2π = 6.28125, 1/44100 = 2.2649765e-05 — so its clock runs 0.1 % slow, as in the original). Validated against a Unicorn emulation of the original thread (x87 control word 0x027F as on Windows): per-sample state identical for the first 3000–6000 samples, note-on events identical (144k events), and the 16-bit PCM identical sample for sample for every second compared (party: 47 s, final: 33 s at the time of writing; the background emulations are slow).
• Shader translation: HLSL mul(v, M) → GLSL M * v (same constructor order); D3D9 pow uses |x|; HLSL smoothstep with reversed edges is spelled out; D3D9 VPOS is an integer pixel coordinate with y down; HLSL implicit truncations (float z *= float3, x + e with float2 + float4, x + e.x scalar broadcast) and the for(;;i++,a=...,b=...) loops whose increment expressions run with i = 1,2,3 are reproduced literally — see the comments in cdak.js.
• The original reads the synth's current position for t, which runs a few tens of ms ahead of what is audible; the port uses the audio clock.
• One quirk kept on purpose: in the final the 24th delay tap's LFO phase lives at the address of the h.x shader constant, so the level the shader sees is the tap phase (level + 2.3e-5).

This port was made with Claude Fable 5.