GameObject with rigid body and attached parts

Physics
1

Hello, this is more a “why does it work” than a “how can I”.

I have some object that can have attached parts.

The base object is big in comparative to subparts.
I have a mesh collider convex for it (yes I know, I should use, primitives, anyway, if physic arise some performance issue I will add some mesh colider with similar mesh with very few pols).
This Base part has rigidbody.

Now I have added some parts that has some primitive collider (but not rigidbody), I add this sub part that visually you can see that collides with the mesh collider of the base, however no weird behavior (tipical of at-force-intersection between colliders -same place-) happen!!.

I mean, It works marvelous!, this sub parts collides with other rigid bodies but not with base class.

so question: “why in the world this works me at once, without problem between inter object collision?”,
I ask this, because maybe it is working now but I should wait some no spected behavior.

Thanks (and unity rocks in productivity ;-).

2

The physics system is designed so that child colliders of a rigidbody object are treated as part of the root collider, so overlapping children don’t collide with each other. The main use of this is to allow primitive colliders on child objects to be positioned and rotated relative to the parent. This lets you approximate a complex shape using the efficient primitive colliders rather than use a mesh collider.