GPU voxel mesh generation and drawing in Unity HDRP

This is an experiment to generate a cubic voxel chunk mesh as efficiently as possible. This is insanely fast, meshing and drawing at around 650 FPS on my RTX 4090. The mesh generation itself is much faster than that, running at more than 1000 FPS with camera disabled.

movie_015.mp4

This example uses a 3D noise library to generate voxel data. You can control frequency, amplitude, offset and speed of the noise via inspector in Unity.

What you can learn from it

• How to create a mesh on gpu
• How to use shader graph with a custom function to draw a mesh using Graphics.DrawProceduralIndirect. This was only recently made possible when Unity added VertexId node to shader graph.

How it works

• generate voxels compute -> voxel data (0/1) is generated using 3d noise
• feedback compute -> iterates all voxels and calculates the count of vertices and indices which will be required for the mesh
• voxelizer compute -> iterates all voxels and writes vertex and index data into the buffers
• the mesh is drawn with Graphics.DrawProceduralIndirect using data from index and vertex buffers

The mesh is generated on the GPU and is never read back to the CPU to create a Mesh object, that would be very slow by comparison (5 FPS).

Credits

• OpenGL voxelizer compute shaders by Demurzasty
• GPU Noise by keijiro