Multiple collider issue

Unity Engine
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1

I have a well. The well is split in 3 mesh renderer materials. You throw rocks in the well with physics. I want the rocks to make a sound when they collide with the well. The sound needs to be different depending on which renderer material of the well it hit.

The first thing I tried was to split the mesh in 3 meshes and have each their own collider, then check which collider is the collision happening with and play a different sound.

This works, BUT, weird things happen in the seams between the colliders (like if a rock goes right between two colliders it goes off in bizarre angles, this doesn’t happen when it’s all one continuous mesh collider).

So I need this to be one single mesh collider.

But if it’s a single mesh and one mesh collider how do I detect which renderer material I am hitting?

I’m thinking of getting the collider contact point, then raycasting to it, so I can then query hitinfo and get triangles, or UV coords or something and use that to figure out which material I’m hitting.

This will probably work, but it seems really roundabout.

Am I missing some other more obvious and easier way to go, or is this it?

2

You can add separate colliders as triggers used just for the sounds. Use Unity - Scripting API: Collider.OnTriggerEnter(Collider)

3

Hmm, with a little bit of offset, right? That could work.

4

You could infer which well surface was hit by checking the direction and position of the hit normal. So if the hit normal is pointing upwards and the hit point is below the well entrance then it’s the water and any other direction is the wall.

5

The wall is made out of 3 separate materials though.