Layer-Based Collision Detection.

In Unity 3.x we introduce Layer-Based collision detection, which is a way to make Game Objects collide with another specific Game Objects that are tied up to specific layers.

In the image above you can see 6 GameObjects, (3 planes, 3 cubes) and the “Collision Matrix” to the right that states which Objects can collide with which layer. In the example, we have set the Collision Matrix in a way that only GameObjects that belong to same layers can collide.

Setting GameObjects to detect Collisions Based on Layers.

1. Select a layer your Game Objects will belong to

2. Repeat 1 for each Game Object until you have finished assigning your Game Objects to the layers.

3. Open the Physics Preference Panel by clicking on Edit->Project Settings->Physics.

4. Select which layers on the Collision Matrix will interact with the other layers by checking them.