I wanted to simulate an object falling above a cloth, but found that it kept falling through no matter what I do, while trying to figure out what's wrong I also found that when I put the object under the cloth, it seems that the collision stays where the object was and didn't really "follow" it. Sorry if I'm not communicating things clearly, I'm new to blender.
It's a classic issue.
As seen in this video at 15:00 : https://www.youtube.com/watch?v=5HRIG04a4X0?t=900
You need to:
- click on the rigid body object (the one which initial position seems to stay where it is and blocks the cloth),
- Go to its Rigid Body properties (in the physics tab),
- Under Collisions, change the Source from "Deform" to "Base".
Another pre-requisite is that Collisions are enabled, additionnally to the Cloth simulation or the Rigid Body simulation (but I can't remember if it has to be on the Cloth or Rigid Body or both)