# Convex Mesh Collider not same as Mesh Filter

I modeled a star in Cheetah and imported it into Unity. When I put a Mesh Collider (with convex enabled) onto the star, the collider boundaries do not match the actual mesh filter; the collider is in the shape if pentagon instead of a star… take a look the the screenshot to see what I mean.

I’m a doing something wrong? Is there a way to have the collider be in the shape of a star?

Thanks.

That’s exactly what “convex” means - there are no inner edges/corners that bend out. If you don’t want that, make it not a convex mesh collider, use a regular one instead.

That’s the definition of Convex. “A convex polygon is defined as a polygon with all its interior angles less than 180°. This means that all the vertices of the polygon will point outwards, away from the interior of the shape. Think of it as a ‘bulging’ polygon. Note that a triangle (3-gon) is always convex.”

So if you want it to actually be the star shape, it cannot be a convex collider.

Also see convex hull, which is what the collider is. It is the smallest convex shape that encompasses the star.

That collider would work for what you want to achieve I’d imagine.

Yeah I guess that is what convex means, but what I was focusing on was that I need an irregularly shaped collider (non primitive)… I need the stars to fit tightly together and I was hoping that mesh collider would do the job (they have to be marked as convex to collide against each other).

I guess I’ll have to use combined primitive colliders. Any ideas and thoughts on this?

Thanks again.

The other alternative is to use several triangle colliders each marked as convex. Then you’ll get the benefit of a convex collider in that it will collide with other meshes and get a better approximation of the actual shape. I’d just do this by setting up the collider objects as non rendering children of the star.

Thanks Jeff. That’s what I decided to do. I simply took the star model and broke it up into 5 parts (each point piece). Worked great.