VkDescriptorMappingSourcePushIndexEXT

The VkDescriptorMappingSourcePushIndexEXT structure is defined as:

typedef struct VkDescriptorMappingSourcePushIndexEXT {
    uint32_t heapOffset;
    uint32_t pushOffset;
    uint32_t heapIndexStride;
    uint32_t heapArrayStride;
    const VkSamplerCreateInfo* pEmbeddedSampler;
    VkBool32 useCombinedImageSamplerIndex;
    uint32_t samplerHeapOffset;
    uint32_t samplerPushOffset;
    uint32_t samplerHeapIndexStride;
    uint32_t samplerHeapArrayStride;
} VkDescriptorMappingSourcePushIndexEXT;

pub struct DescriptorMappingSourcePushIndexEXT {
    heap_offset: u32,
    push_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_push_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.
• pushOffset is an index into push 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 push 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.
• samplerPushOffset is used only when mapping a combined image sampler, used in place of pushOffset 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

• pushIndex = ((uint32_t*)pPushData)[pushOffset/4]
• shaderIndex = (Binding - firstBinding) + arrayIndex
• offset = heapOffset + (pushIndex × 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 pPushData is the total set of push data specified by vkCmdPushDataEXT.

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

• samplerPushIndex = ((uint32_t*)pPushData)[samplerPushOffset/4]
• offset = samplerHeapOffset + (samplerPushIndex × samplerHeapIndexStride) + (shaderIndex × samplerHeapArrayStride)

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

• pushIndex = ((uint32_t*)pPushData)[pushOffset/4] & 0xFFFFF
• samplerPushIndex = (((uint32_t*)pPushData)[pushOffset/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.