Summary

Creating optimal meshes for ray tracing is crucial for achieving high-performance rendering. Unlike rasterization, ray tracing requires specific handling of mesh properties to avoid performance issues. This article explores the key considerations for creating optimal meshes, including avoiding elongated triangles, rebuilding deformable meshes, handling degenerate triangles, merging and splitting meshes judiciously, and optimizing alpha-tested meshes.

Understanding Ray Tracing Mesh Requirements

Ray tracing is a rendering technique that simulates the lighting of a scene and its objects by rendering physically accurate reflections. However, creating optimal meshes for ray tracing is different from creating meshes for rasterization-based rendering. Some mesh properties that are acceptable in rasterization can be problematic in ray tracing or require specific handling to work as expected.

Avoiding Elongated Triangles

Elongated triangles can cause performance issues in ray tracing. These triangles have a large aspect ratio, which can lead to inefficient bounding volume hierarchy (BVH) traversal. To avoid this, it’s essential to split elongated triangles into smaller, more evenly shaped triangles. This results in better ray-tracing performance.

Rebuilding Deformable Meshes

Deformable meshes, such as skinned characters or blend shapes, require rebuilding to ensure optimal performance. Rebuilding the mesh helps to maintain a tight bounding volume hierarchy, which is essential for efficient ray tracing. Failure to rebuild deformable meshes can lead to performance issues.

Handling Degenerate Triangles

Degenerate triangles, which have zero area, can cause issues in ray tracing. These triangles can lead to incorrect intersection results and affect performance. It’s essential to handle degenerate triangles carefully, either by removing them or using specific techniques to mitigate their impact.

Merging and Splitting Meshes Judiciously

Merging meshes or merging several triangle mesh geometries into one bottom-level acceleration structure (BLAS) can be beneficial. Tracing a ray against a merged structure is often faster than against separate pieces. However, merging should be done judiciously, considering factors such as the proximity of geometries and their movement relative to each other.

Optimizing Alpha-Tested Meshes

Alpha testing can slow down ray tracing as it interrupts the hardware intersection search. Optimizing alpha-tested meshes involves minimizing the number of alpha-tested surface layers crossed by rays. This can be achieved by cutting off fully transparent areas of alpha-tested meshes and splitting the mesh into alpha-tested and fully opaque parts.

Best Practices for Creating Optimal Meshes

To create optimal meshes for ray tracing, follow these best practices:

  • Avoid elongated triangles: Split elongated triangles into smaller, more evenly shaped triangles.
  • Rebuild deformable meshes: Rebuild deformable meshes to maintain a tight bounding volume hierarchy.
  • Handle degenerate triangles: Remove or mitigate degenerate triangles to avoid performance issues.
  • Merge and split meshes judiciously: Merge meshes considering their proximity and movement relative to each other.
  • Optimize alpha-tested meshes: Minimize alpha-tested surface layers and split meshes into alpha-tested and opaque parts.

Conclusion

Creating optimal meshes for ray tracing is crucial for achieving high-performance rendering. By understanding the specific requirements of ray tracing and following best practices, developers can create meshes that are optimized for efficient rendering. Avoiding elongated triangles, rebuilding deformable meshes, handling degenerate triangles, merging and splitting meshes judiciously, and optimizing alpha-tested meshes are key considerations for creating optimal meshes. By applying these principles, developers can ensure that their meshes are optimized for ray tracing, leading to better performance and more realistic rendering results.