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graphicsvulkan
rich.e
rich.e

Reputation: 3750

Understanding Vulkan uniform layout's 'set' index

I've been following along in the (very awesome) nvpro raytracing tutorial and have a question about the way the CameraProperties uniform buffer is bound using layout(binding = 0, set = 1) - I understand the binding = 0, but why set = 1?

The tutorial says "The set = 1 comes from the fact that it is the second descriptor set passed to pipelineLayoutCreateInfo.setPSetLayouts", but when I look at HelloVulkan::createGraphicsPipeline() I see the layout count is one, and this is where m_descSetLayout (what binds the camera uniform buffer) is used. What am I missing?

The related section of the tutorial is here.

Thanks!

Upvotes: 3

Views: 1521

Answers (1)

Sascha Willems
Sascha Willems

Reputation: 5828

See chapter 7.1:

  std::vector<vk::DescriptorSetLayout> rtDescSetLayouts = {m_rtDescSetLayout, m_descSetLayout};
  pipelineLayoutCreateInfo.setSetLayoutCount(static_cast<uint32_t>(rtDescSetLayouts.size()));
  pipelineLayoutCreateInfo.setPSetLayouts(rtDescSetLayouts.data());

The pipeline layout contains two descriptor set layouts, m_rtDescSetLayout for the acceleration structures at index 0 (set 0) and m_descSetLayout for the screne descriptors in index 1 (set 1). In Vulkan the set is automatically derived from a descriptor set layout's index in the pipeline layouts create info.

Upvotes: 4

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