C Specification
To get the offset of a binding within a descriptor set layout in memory, call:
// Provided by VK_EXT_descriptor_buffer
void vkGetDescriptorSetLayoutBindingOffsetEXT(
VkDevice device,
VkDescriptorSetLayout layout,
uint32_t binding,
VkDeviceSize* pOffset);
Parameters
-
device
is the logical device that gets the offset. -
layout
is the descriptor set layout being queried. -
binding
is the binding number being queried. -
pOffset
is a pointer to VkDeviceSize where the byte offset of the binding will be written.
Description
Each binding in a descriptor set layout is assigned an offset in memory by the implementation. When a shader accesses a resource with that binding, it will access the bound descriptor buffer from that offset to look for its descriptor. This command provides an application with that offset, so that descriptors can be placed in the correct locations. The precise location accessed by a shader for a given descriptor is as follows:
-
location = bufferAddress + setOffset + descriptorOffset + (arrayElement × descriptorSize)
where bufferAddress and setOffset are the base address and
offset for the identified descriptor set as specified by
vkCmdBindDescriptorBuffersEXT and
vkCmdSetDescriptorBufferOffsetsEXT, descriptorOffset is the
offset for the binding returned by this command, arrayElement is the
index into the array specified in the shader, and descriptorSize is
the size of the relevant descriptor as obtained from
VkPhysicalDeviceDescriptorBufferPropertiesEXT.
Applications are responsible for placing valid descriptors at the expected
location in order for a shader to access it.
The overall offset added to bufferAddress to calculate location
must be less than
VkPhysicalDeviceDescriptorBufferPropertiesEXT::maxSamplerDescriptorBufferRange
for samplers and
VkPhysicalDeviceDescriptorBufferPropertiesEXT::maxResourceDescriptorBufferRange
for resources.
If any binding
in layout
is
VK_DESCRIPTOR_BINDING_VARIABLE_DESCRIPTOR_COUNT_BIT
, that
binding
must have the largest offset of any binding
.
A descriptor binding
with type VK_DESCRIPTOR_TYPE_MUTABLE_VALVE
can be used.
Any potential types in
VkMutableDescriptorTypeCreateInfoVALVE::pDescriptorTypes
for
binding
share the same offset.
If the size of the mutable descriptor is larger
than the size of a concrete descriptor type being accessed, the padding area
is ignored by the implementation.
Document Notes
For more information, see the Vulkan Specification
This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.