Fix instance data stride.#1691
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bkaradzic-microsoft merged 3 commits intoBabylonJS:masterfrom May 9, 2026
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bgfx exposes instance data as a sequence of float4 registers (TEXCOORD7..0), and the D3D11 input layout binds each one at a hard-coded offset of slotIdx*16, so stride must be a multiple of 16 and each attribute must be 16-byte-padded. The previous code summed ElementSize directly, which both tripped bgfx's 'Stride must be multiple of 16' assert and placed sub-vec4 attributes at the wrong offsets within their slots. Now each instance attribute occupies one 16-byte slot, the buffer is zeroed first, and we early-return on empty/zero instance counts. Lifts 36 of the 58 affected particle/instance tests from crash to pass; the remaining 22 still render but fail pixel-diff for unrelated reasons. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
…stride fix. After the bgfx instance-data stride fix in this branch, 36 of the 58 previously-affected particle/instance tests now pass and are re-enabled so CI can verify the fix. The remaining 22 tests no longer crash but still fail pixel-diff for reasons unrelated to stride alignment (likely shader-side packing of vec3+float into shared vec4 instance slots); their exclusion reason is updated to reflect the post-fix state and to flag the follow-up work. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR updates BabylonNative’s bgfx instance-data packing to use 16-byte slots per instance attribute (matching bgfx’s expected i_dataN layout), addressing stride/alignment assertions and stabilizing instanced rendering across backends. It also adjusts Playground validation configuration to re-enable tests that were previously excluded due to the stride issue and to update exclusion reasons for remaining problematic scenes.
Changes:
- Align instance data stride/padding to fixed 16-byte slots per instance attribute and zero-fill unused bytes.
- Make instance-data buffer construction robust to empty inputs and inferred instance counts.
- Re-enable several Playground validation tests previously disabled due to bgfx stride assertions; update exclusion reasons for others.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| Plugins/NativeEngine/Source/VertexBuffer.cpp | Packs instance attributes into fixed 16-byte slots, zero-fills padding, and adjusts stride computation to satisfy bgfx alignment expectations. |
| Apps/Playground/Scripts/config.json | Re-enables previously excluded tests tied to the stride issue and updates remaining exclusion reasons. |
bghgary
approved these changes
May 8, 2026
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