VkAccelerationStructureTrianglesOpacityMicromapEXT

The VkAccelerationStructureTrianglesOpacityMicromapEXT structure is defined as:

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

• sType is a VkStructureType value identifying this structure.
• pNext is NULL or a pointer to a structure extending this structure.
• indexType is the type of triangle indices used when indexing this micromap
• indexBuffer is the address containing the triangle indices
• indexStride is the byte stride between triangle indices
• baseTriangle is the base value added to the non-negative triangle indices
• usageCountsCount specifies the number of usage counts structures that will be used to determine the size of this micromap.
• pUsageCounts is a pointer to an array of VkMicromapUsageEXT structures.
• ppUsageCounts is a pointer to an array of pointers to VkMicromapUsageEXT structures.
• micromap is the handle to the micromap object to include in this geometry

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 VK_NULL_HANDLE, then every value read from indexBuffer must be one of the values in VkOpacityMicromapSpecialIndexEXT.