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This is a paid asset, but now you can download Terrain Spam Free.
Terrain Spam v1.0
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Terrain Spam allows level designers and developers create high volume and complex scenes with large amounts of objects in a much shorter amount of time.
– Optionally preserve prefab connections
– Select gameobjects to choose randomly from
– Automatically apply random or defined position, rotation, and scale
– Optionally snap to grid or intervals
– Auto assign a parent to created objects
– Layer masks for unwanted terrains
In a few steps you can begin placing many objects with a tap of the Spacebar.
You can also apply random settings and offsets to already created objects!