triangle-object-positions-without-allow-data-access-flag

Status: shipped (Phase 8) — see CHANGELOG.

What it detects

Every call site of TriangleObjectPositions() (SM 6.10 ray-tracing intrinsic). Project-side state (the BLAS-build flag) is invisible from shader source, so the rule fires on every call site as a reminder.

Why it matters on a GPU

TriangleObjectPositions() requires the underlying acceleration structure to have been built with D3D12_RAYTRACING_GEOMETRY_FLAG_USE_ORIENTED_BOUNDING_BOX (D3D12) or VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DATA_ACCESS_BIT_KHR (Vulkan). Without the flag, the call is undefined behaviour: drivers may return garbage positions, segfault, or silently fall back to an older BVH layout.

Examples

Bad

[shader("closesthit")]
void ch(inout Payload p, in Attribs a) {
    float3 v[3] = TriangleObjectPositions(); // verify BLAS flag
}

Good

CPU-side: ensure the BLAS build sets the USE_ORIENTED_BOUNDING_BOX / ALLOW_DATA_ACCESS flag. Once verified, this rule's diagnostic can be suppressed inline.

Options

none

Fix availability

none — Project-side configuration cannot be inspected from shader source.

See also

• Vulkan: VK_KHR_ray_tracing_position_fetch
• DirectX SM 6.10 preview blog