ray_trace

Vulkan Raytracing Implementation

Overview

This sample demonstrates basic raytracing in Vulkan, featuring GGX shading, shadows, and reflections.

Descriptor Heap

Resources are bound bindless through VK_EXT_descriptor_heap via nvvk::DescriptorHeap, instead of descriptor sets. This is the reference for descriptor heaps on a ray-tracing pipeline: ray-tracing stages cannot be shader objects, so the VkRayTracingPipeline opts in with VK_PIPELINE_CREATE_2_DESCRIPTOR_HEAP_BIT_EXT and is created with layout == VK_NULL_HANDLE (no VkPipelineLayout); push data is sent with vkCmdPushDataEXT.

The output storage image and the scene-info buffer are written into the heap. The TLAS is not stored in the heap — it is passed by device address in the push data and turned into an acceleration structure in-shader via RaytracingAccelerationStructure(address). See the descriptor_heap sample for the concept in depth, and simple_polygons for the same idea on a raster pipeline.

Key Components

onAttach() Method

• Initializes utility classes for:
  • Top-Level Acceleration Structure (TLAS)
  • Bottom-Level Acceleration Structure (BLAS)
  • Shading Binding Table (SBT)
• Scene creation and buffer uploading
• Acceleration structure generation
• Ray tracing pipeline setup

onUIRender() Method

• UI rendering
• Full viewport image display

onRender(cmd) Method

• Frame information buffer updates
• vkCmdTraceRaysKHR invocation

Implementation Details

1. Scene Creation: createScene()
2. Vulkan Buffer Generation: createVkBuffers()
3. Acceleration Structures:
   • BLAS: createBottomLevelAS()
   • TLAS: createTopLevelAS()
4. Pipeline Creation: createRtPipeline()
   • Shader attachment (raygen, miss, closest-hit)

Technical Considerations

• Optimization of acceleration structure updates
• Efficient SBT management
• Performance tuning for real-time raytracing

Note

For global illumination implementations, refer to the gltf_viewer sample.