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Sample source

Browse the full sample on GitHub: raytrace_tutorial/02_basic

02 Basic Ray Tracing - Tutorial

02 Basic ray tracing result

This tutorial demonstrates the foundational ray tracing implementation by converting the raster foundation to use ray tracing pipelines. It introduces the core concepts of ray-based rendering with acceleration structures, ray generation, closest hit, and miss shaders. This serves as the essential foundation that all subsequent ray tracing tutorials build upon.

Key Features

  • Ray Tracing Pipeline: Multi-stage shader pipeline for ray-based rendering
  • Acceleration Structures: BLAS and TLAS for efficient ray-geometry intersection
  • Shader Binding Table: Management system for ray tracing shaders
  • Ray Generation: Camera ray creation and dispatch
  • Closest Hit Shading: Material shading at ray intersection points
  • Miss Shader: Background/sky rendering for rays that miss geometry

Architecture Overview

This implementation transforms the raster foundation by replacing the traditional graphics pipeline with a ray tracing pipeline. Instead of rasterizing triangles, rays are generated from the camera and traced through the scene using acceleration structures for efficient intersection testing.

Pipeline Type: Ray tracing pipeline vs graphics pipeline
Shader Types: Ray generation, closest hit, miss shaders
Geometry Handling: Acceleration structures (BLAS/TLAS)
Rendering Method: vkCmdTraceRaysKHR vs vkCmdDrawIndexed

Key Components

  • Acceleration Structures: BLAS for geometry, TLAS for instances
  • Shader Binding Table: Ray tracing shader management
  • Ray Tracing Pipeline: Multi-stage shader pipeline
  • Descriptor Bindings: TLAS and output image bindings

Shader Structure

Ray Generation Shader

[shader("raygeneration")]
void rgenMain()
{
    // Generate camera rays and trace them
    RayDesc ray;
    ray.Origin = cameraPosition;
    ray.Direction = normalize(rayDirection);
    TraceRay(topLevelAS, rayFlags, 0xff, 0, 0, 0, ray, payload);
}

Closest Hit Shader

[shader("closesthit")]
void rchitMain(inout HitPayload payload, in BuiltInTriangleIntersectionAttributes attr)
{
    // Basic material shading at intersection point
    payload.color = float3(1, 0, 0); // Simple red color
}

Miss Shader

[shader("miss")]
void rmissMain(inout HitPayload payload)
{
    // Sky/background color for rays that miss geometry
    payload.color = float3(1, 1, 1); // White background
}

Key Differences from Foundation

  1. Pipeline Type: Graphics pipeline → Ray tracing pipeline
  2. Shader Types: Vertex/Fragment → Ray generation/Closest hit/Miss
  3. Geometry: Vertex buffers → Acceleration structures
  4. Rendering: vkCmdDrawIndexed → vkCmdTraceRaysKHR
  5. Descriptors: Added TLAS and output image bindings
  6. Memory: Added SBT buffer for shader binding table

Implementation Highlights

This basic implementation enables: - Global Illumination: Rays can bounce and gather lighting from any direction - Accurate Reflections: Perfect mirror-like surfaces without approximation - Complex Lighting: Multiple light sources with proper shadow casting - Future Extensions: Foundation for advanced effects like transparency, motion blur, and callable shaders

Next Steps

For step-by-step conversion guide, see rt_tutorial

This basic implementation can be extended with: - 03_any_hit - for transparency and alpha testing - 04_jitter_camera - for temporal anti-aliasing - 05_shadow_miss - for efficient shadow testing - 06_reflection - for mirror-like surfaces and global illumination - 07_multi_closest_hit - for different materials per object - 09_motion_blur - with animated acceleration structures

For detailed information about the core ray tracing components: