scene: cone prepass for pass 1, opt-in steps/pixel readout #12
2026-11-04
scene README: createScene needs either float colour-buffer extension
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
scene: half-float prepass start target where EXT_color_buffer_float is missing; say why createScene is null
Phone Chrome without EXT_color_buffer_float returned null with one message. Rendering to RGBA16F only needs EXT_color_buffer_half_float, and every other target is already a half, so only the prepass start (RGBA32F) needed a fallback. In half mode the prepass writes t*(1-2^-10) - 2^-15, which stays below t after the half rounds to nearest, so pass 1 still starts at or before the true distance. W_FAR stays exact. onUnavailable names no-webgl2 vs neither float extension; Scene.startFormat and options.halfStart (force, for tests and the harness). The standalone page shows the reason, renderer, vendor, UA and extension list. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
harness: demo page keeps hold of the canvas it swaps in, so the prepass switch works twice
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
scene: pack step bytes tightly; keep the hit tolerance clear at the far end of a prepass step
Soul pass on 87c9ca60: the R8 steps read used the default PACK_ALIGNMENT of 4, so
at widths not divisible by 4 the buffer was too small (readPixels fails) and padding
would be summed. Portrait runs read 0 steps/pixel. The prepass step now divides by
1.0006 so pass 1's tolerance, which grows with t, stays clear at the end of the step.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
harness: trace and diff modes, standalone demo page with steps/pixel readout
trace: steps per pixel and pass ms at three fixed camera poses, PREPASS=0,1 arms. diff: one frozen frame with and without the prepass, against a 512-step render. bundle.cjs demo: full-window page with a prepass switch and the readout. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
scene: cone prepass starts pass-1 rays past empty space; opt-in steps/pixel readout
Pass 0 marches one ray per 8x8 tile of pass 1, each step shrunk by the widest any ray of the tile strays from it, and stores the distance no ray of the tile can have hit before (W_FAR when the whole tile climbs out above the highest geometry). Pass 1 starts from it. The distance bound moves to sdf.glsl so both passes step by the same function. onTraceStats adds a step-count render target to pass 1 and reads it back every 8th frame through a pixel-pack buffer and fence, outside the timed span. Unset, neither the output nor the target exists. prepass:false is the baseline. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>