b645746c8c
Adds an 8^3 = 512-instance TLAS pick test that shoots one analytically determined ray through a rayQuery=true PlainComputeShader and checks the read-back committed hit (customIndex 484, t 40.75). 512 instances sit in the < 8193 regime that the hardcoded 16384-leaf start used to miss, so the example fails fast if the shim regresses. Verified in Firefox/WebGPU: "[RayQueryPick] PASS". Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
35 lines
1.4 KiB
Markdown
35 lines
1.4 KiB
Markdown
# RayQueryPick
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Regression test for the WebGPU software **ray-query** shim
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(`additional/dom-webgpu.js`, `_rqTraverseTlas`).
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Builds an 8³ = 512-instance TLAS and shoots one fully-determined ray
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through a `rayQuery=true` `PlainComputeShader`. The committed hit is read
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back to the host and checked against the analytically-known answer
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(instance `customIndex = 484`, `t = 40.75`). On success the console prints:
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```
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[RayQueryPick] result: hit=1 customIndex=484 prim=6 t=40.75
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[RayQueryPick] PASS — rayQuery TLAS traversal hit the expected instance
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```
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## Why 512 instances
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The TLAS sweep tree is padded to `next_pow2(instanceCount)` leaves. The
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rayQuery shim used to detect BVH leaves with a hardcoded `16384 - 1` leaf
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start, so for any scene with fewer than 8193 instances **no node index
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ever reached a leaf** and every pick missed (issue #25). 512 sits squarely
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in that broken regime, so this example fails fast if the shim regresses to
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a static leaf start. The shim now derives the leaf start from a per-build
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`RqTlasMeta.nPadded` uniform, matching the megakernel `_rtwTraverseTlas`.
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The scene also renders through the wavefront RT pipeline (same as
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RTStress) so the run produces a visible frame, but the pass/fail signal is
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the console line above.
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```bash
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cd examples/RayQueryPick
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crafter-build -r --target=wasm32-wasip1
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```
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WebGPU/DOM only — the native path uses hardware ray queries.
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