What are the "interactions" in 2d-BoxPushing and 3d-BoxPushing?

[Luodian]

Hi, Kipf~I really appreciate your work. I am wondering if the GNN is modeling interactions between objects.

After heading over the codes, I found that when collision happens from object A to object B, there's no bouncing back of object A and pushing forward happens to object B. So what are the interactions in 2d-boxpushing and 3d-boxingpushing experiments. The objects in those two experiments are more like independent with each other.

For 3-body physics, I understand the interactions are the forces among spheres.

Best regards.