New to Grass Stamper? Follow the step-by-step Grass Stamper — Getting Started tutorial first.
Supported resource types
Grass Stamper supports:For spawning GameObjects and Terrain Objects, use Object Stamper. For painting terrain textures, use Texture Stamper.
How it works
When you click Spawn, Grass Stamper processes each active Group in order:- Casts a ray downward from the stamper’s position to find the surface.
- Builds the box area from the result.
- Iterates over all Unity Terrains that intersect the stamper bounds.
- For each terrain and each active detail prototype, runs the detail spawn routine.
Detail spawn routine per terrain
For each Terrain Detail prototype on each intersecting terrain, the stamper:- Converts the box area into detail-map coordinates.
- Reads the existing detail layer.
- For each detail cell in the area, evaluates the Mask Filter fitness for that prototype.
- Computes a target density:
- If Use Random Opacity is enabled: multiplies fitness by a random value before scaling to the density range.
- Otherwise: scales fitness directly to the density range.
- Applies a random failure check using Failure Rate.
- Writes the result back to the terrain detail layer.
Grass Stamper requires that the terrain’s detail prototypes are already configured in Unity’s Terrain Inspector. If no detail prototypes exist on the terrain, the stamper logs a warning and skips that terrain.
Shared systems
Per-prototype settings (Unity/Terrain Detail)
- Spawn Detail Settings — controls detail density, opacity, and failure rate.
- Mask Filters — each prototype has its own independent mask filter stack.
Tool-level components
- Area Settings — defines the stamper volume and bounds.
- Stamper Tool Controller — controls visualization and auto respawn.
- Layer Settings — specifies which physics layers are used for raycasts.
Auto Respawn behavior
When Auto Respawn is on in the Stamper Tool Controller, changing a Terrain Detail prototype setting triggers a respawn of only that specific detail prototype on the terrain, not the entire Group. This makes real-time tuning of individual detail layers fast and non-destructive.When to use Grass Stamper
Grass Stamper is best when you want:- a one-shot density pass for grass, flowers, or mesh details across a large terrain;
- per-prototype mask filter control so each grass type has independent placement rules;
- a stamper workflow for detail that mirrors how Object Stamper handles objects.