Structure specifying an opacity micromap in a bottom-level acceleration structure.

Description

If VkAccelerationStructureTrianglesOpacityMicromapEXT is included in the pNext chain of a VkAccelerationStructureGeometryTrianglesDataKHR structure, that geometry will reference that micromap.

For each triangle in the geometry, the acceleration structure build fetches an index from indexBuffer using indexType and indexStride. If that value is the unsigned cast of one of the values from VkOpacityMicromapSpecialIndexEXT then that triangle behaves as described for that special value in Ray Opacity Micromap. Otherwise that triangle uses the opacity micromap information from micromap at that index plus baseTriangle.

Only one of pUsageCounts or ppUsageCounts can be a valid pointer, the other must be NULL. The elements of the non-NULL array describe the total count used to build this geometry. For a given format and subdivisionLevel the number of triangles in this geometry matching those values after indirection and special index handling must be equal to the sum of matching count provided.

If micromap is NULL_HANDLE, then every value read from indexBuffer must be one of the values in VkOpacityMicromapSpecialIndexEXT.

Valid Usage

• Only one of pUsageCounts or ppUsageCounts can be a valid pointer, the other must be NULL

Valid Usage (Implicit)

• sType must be STRUCTURE_TYPE_ACCELERATION_STRUCTURE_TRIANGLES_OPACITY_MICROMAP_EXT
• indexType must be a valid VkIndexType value
• If usageCountsCount is not 0, and pUsageCounts is not NULL, pUsageCounts must be a valid pointer to an array of usageCountsCount VkMicromapUsageEXT structures
• If usageCountsCount is not 0, and ppUsageCounts is not NULL, ppUsageCounts must be a valid pointer to an array of usageCountsCount valid pointers to VkMicromapUsageEXT structures
• If micromap is not NULL_HANDLE, micromap must be a valid VkMicromapEXT handle

See Also

VkDeviceOrHostAddressConstKHR, VkMicromapUsageEXT

Layout

struct VkAccelerationStructureTrianglesOpacityMicromapEXT {
    VkStructureType sType;
    void * pNext;
    VkIndexType indexType;
    VkDeviceOrHostAddressConstKHR indexBuffer;
    VkDeviceSize indexStride;
    uint32_t baseTriangle;
    uint32_t usageCountsCount;
    VkMicromapUsageEXT const * pUsageCounts;
    VkMicromapUsageEXT const * const * ppUsageCounts;
    VkMicromapEXT micromap;
}