vkUpdateDescriptorSets in case of instancing

Vulkan
1

Hello guys! Could you please explain why in case of instancing in Sascha Willems VULKAN examples we are not calling vkUpdateDescriptorSets for buffer(instanceBuffer.buffer) which contains instance rotate/translation/scale?

If I try to do it the I am getting error

vkUpdateDescriptorSets(): pDescriptorWrites[0].pBufferInfo[0].buffer was created with VK_BUFFER_USAGE_2_TRANSFER_DST_BIT_KHR|VK_BUFFER_USAGE_2_VERTEX_BUFFER_BIT_KHR, but descriptorType is VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER. The Vulkan spec states: If descriptorType is VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER or VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC, the buffer member of each element of pBufferInfo must have been created with VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT set

2

I’m not familiar with the tutorial in question, but given the usage flags, this buffer is intended for use with vertex data. It’s not a uniform buffer; it’s not access directly by the shader as a shader resource, so it is not a descriptor. You bind it with vkCmdBindVertexBuffers.

1 Like
3

This buffer is not VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT. It is created as VK_BUFFER_USAGE_VERTEX_BUFFER_BIT. And it means that I do not need to link this buffer to VkDescriptorSet? And at the same time I can get buffer data in shader through location which I define in VkVertexInputBindingDescription and VkVertexInputAttributeDescription for my VkPipeline?

4

Exactly. Per-instance data as passed a vertex data in that sample (with per-instance rate). And you don’t need descriptors for vertex buffers.

1 Like
5

Great! Thanks a lot ))))) Your examples are very helpfull

6

This topic was automatically closed 183 days after the last reply. New replies are no longer allowed.