Physics collision super newb

When I create two boxes, add physics rigidbody to them both. Put one below the other, set the bottom one (the ground) to Kinematic as i don't want it to fall and push play. The first box always falls right through the other. I tried making the bottom box bigger but it still falls right through. What am I missing, I feel dumb...

Make sure it has colliders on it, that will usually solve the problem. if they have colliders make sure the colliders are both triggers or not triggers, if they are different they will never interact.

OK, figured it out. Hope this helps someone else. You need to make sure your objects are in the same collision groups. This matrix can be found under Edit->Project Settings->Physics.

for two objects to collide in physics simulations,

  1. both should have a collider
  2. the colliders should not have "is trigger" enabled
  3. the moving object should not be a kinematic rigidbody (i.e isKinematic should be false)
  4. the moving object should have a rigidbody attached
  5. there is a collision matrix in project settings>physics, in the matrix layers of the objects should have collision with each other, i mean both objects should be on layers that have collision with each other.