Masks

GPU Grass places and renders objects on the GPU based on masks.

6 masks are generated per terrain.

• Normal
• Terrain Color
• Heightmap
• Slope
• Terrain Layer
• Collision Mask

3 masks are generated per object type.

• Placement
• Color
• Scale

These masks are generated in the editor and updated when something changes. They are packed into textures and sent to the GPU.

 

---

 

Runtime

These 3 steps happen every frame on the GPU.

Step 1: Placement

Positions are generated in a compute shader.

1. GPU Grass uses either random values or blue noise to generate positions.
2. Positions are filtered based on the placement mask.
3. Positions are sorted into LODs.

Step 2: Culling

• Positons are culled using the camera's frustum.

Step 3: Rendering

• Objects are rendered using Graphics.DrawMeshInstancedIndirect
• Scale, rotation and other data is calculated in the shader based on masks.