Colliding 2 completely flat quads with physics?

Imagine you have imported 2 completely flat 2d quads from some 3d app and they are now in the Unity scene, positioned so that you're basically looking at them as two squares on the screen side by side, not necessarily touching.

Now, with Unity's physics (colliders, rigidbody, whatever), if I push one of those quads horizontally toward the other quad so that their edges would collide, will it actually collide or will they pass right through each other?

My concern is that the quads have `no depth` and therefore they won't collide? ie I guess the physics system cannot do proper 2d you have to always have some depth to your objects to make them collide?

No, you can't have completely flat moving physics objects (rigidbodies).

You can have completely flat objects which act as Static Colliders - for example, a ground plane which doesn't move. To do this, you would just have a plane with a collider component but no rigidbody component attached.

However, if you have a completely flat object (eg, unity's built-in plane), with a Mesh Collider (so that it uses the objects mesh as the collision volume), and you try to add a Rigidbody component, you will get an error from the physics engine.

This is because the rigidbody needs some volume in order to have mass, inertia, and these things are impossible to compute if the rigidbody has no volume.

If you assign a Box Collider to a game object with a completely flat mesh, the box collider will automatically give itself a tiny amount of depth so that it performs correctly.

Use box colliders for the quads.

So there is no such thing as a flat collider that will collide edge-on, it has to be a collider with depth?

I have same problem i need to have collision bettwen particles in xoy plane and a 2d map also in xoy plane but i can not find a way to do it... if u got any solutions that oyu can share it will be good

well the colliders are invisible so you can make the collider thicker, anyway way i see it but i get what you saying bu cant say i have tried it and you can make the colliders a faction whider so you wont notice how close they might come,.