Dynamic Mesh Collider from Vertex Position

Hello.

I have a material with a dynamic vertex animation, although moving the vertices around do not modify the collider accordingly. How can I get the mesh collider on it to change with the vertex positions ?

Thanks.

 

If you are moving the vertices in a shader then you will not be able to update the collider, you will need to do the same deformation in script and then reset the mesh collider, this is very very slow for anything other than a simple mesh.

 

Is there an alternative way to modify the colliders with the vertex animations ?

 

The only way to modify a mesh collider is build a mesh with the vertices in their position and then update the collider mesh by setting it to that mesh, so you would either have to do whatever deformation you are doing in your shader in script and update the mesh vertex positions and then set the collider to that. Which then rather defeats the purpose of having it in the shader. Only other alternative is to have a simpler proxy mesh to use as the collider and then deform that in script and update the collider with that.

 

I see. Seems like there is no practical way to do it without compromise.
Thanks.

 

Moving the vertices of a mesh and making it the new collider mesh source isn't complicate and isn't that slow.
Bui I also found this paper: http://beta.unity3d.com/talks/Siggraph2011_SpecialEffectsWithDepth_WithNotes.pdf
where it states that with Z-depth a shader can determinate a "collision" (if it is the last to be drawn and if a pixel z-depth value is close enough to what was store before in z-depth buffer), so I guess that you could read this value from your shader and trigger something in response...

 

One workaround would be to use a larger collider (box instead of polygon) which covers the entire area where the mesh could be deformed to. On the collision event you could simply check if the colliding object intersects your intended hit zone (the mesh) and otherwise dismiss the collision.