VkDescriptorMappingSourceShaderRecordIndexEXT

The VkDescriptorMappingSourceShaderRecordIndexEXT structure is defined as:

typedef struct VkDescriptorMappingSourceShaderRecordIndexEXT {
    uint32_t heapOffset;
    uint32_t shaderRecordOffset;
    uint32_t heapIndexStride;
    uint32_t heapArrayStride;
    const VkSamplerCreateInfo* pEmbeddedSampler;
    VkBool32 useCombinedImageSamplerIndex;
    uint32_t samplerHeapOffset;
    uint32_t samplerShaderRecordOffset;
    uint32_t samplerHeapIndexStride;
    uint32_t samplerHeapArrayStride;
} VkDescriptorMappingSourceShaderRecordIndexEXT;

pub struct DescriptorMappingSourceShaderRecordIndexEXT {
    heap_offset: u32,
    shader_record_offset: u32,
    heap_index_stride: u32,
    heap_array_stride: u32,
    p_embedded_sampler: *const vk::SamplerCreateInfo,
    use_combined_image_sampler_index: vk::Bool32,
    sampler_heap_offset: u32,
    sampler_shader_record_offset: u32,
    sampler_heap_index_stride: u32,
    sampler_heap_array_stride: u32,
}

• heapOffset is a constant byte offset added to the heap address for the mapped resource or sampler.
• shaderRecordOffset is an index into shader record data where an index into the heap for the mapped resource will be retrieved.
• heapIndexStride is a constant byte stride that multiplies the index in shader record data.
• heapArrayStride is a constant byte stride that multiplies the shader binding and array index.
• pEmbeddedSampler is an optional VkSamplerCreateInfo structure specifying a sampler to embed into the shader, in place of looking the sampler up in a heap.
• useCombinedImageSamplerIndex specifies whether the generated index value will be decoded as two packed indices if the mapped resource is an OpTypeSampledImage.
• samplerHeapOffset is used only when mapping a combined image sampler, used in place of heapOffset to retrieve the sampler.
• samplerShaderRecordOffset is used only when mapping a combined image sampler, used in place of shaderRecordOffset to retrieve the sampler.
• samplerHeapIndexStride is used only when mapping a combined image sampler, used in place of heapIndexStride to retrieve the sampler.
• samplerHeapArrayStride is used only when mapping a combined image sampler, used in place of heapArrayStride to retrieve the sampler.

Resources using this mapping will be backed by a descriptor in the heap, at an offset calculated as

• shaderRecordIndex = ((uint32_t*)pShaderRecordData)[shaderRecordOffset/4]
• shaderIndex = (Binding - firstBinding) + arrayIndex
• offset = heapOffset + (shaderRecordIndex × heapIndexStride) + (shaderIndex × heapArrayStride)

where Binding is the binding value in the shader, arrayIndex is the index into the array if the shader binding is declared as an array, and pShaderRecordData is the set of shader record data accessible to the shader.

If the mapped resource is a OpTypeSampledImage, offset is instead calculated for the sampler as

• samplerShaderRecordIndex = ((uint32_t*)pShaderRecordData)[samplerShaderRecordOffset/4]
• offset = samplerHeapOffset + (samplerShaderRecordIndex × samplerHeapIndexStride) + (shaderIndex × samplerHeapArrayStride)

If useCombinedImageSamplerIndex is VK_TRUE, and the mapped resource is a OpTypeSampledImage, shaderRecordIndex and samplerShaderRecordIndex in the above equations are instead calculated as

• shaderRecordIndex = ((uint32_t*)pShaderRecordData)[shaderRecordOffset/4] & 0xFFFFF
• samplerShaderRecordIndex = (((uint32_t*)pShaderRecordData)[shaderRecordOffset/4] >> 20) & 0xFFF

If the mapped resource is a OpTypeSampler or OpTypeSampledImage, and pEmbeddedSampler is not NULL, the specified embedded sampler will be used rather than accessing the sampler heap.