Wrong normal over floor edge, no floor detected (2D)

[berarma]

Tested versions

• Reproduclibe in: 4.2.1 and 4.3-dev6

System information

Debian GNU/Linux 12.5

Issue description

Collisions between the edges of rectangle shapes are obviously wrong. An object falling and being stopped by an edge can't have a normal pointing to one side (in the X axis). All movements and shape edges are parallel to axes. In this case, any object stopping another object from falling has to be floor and have a normal pointing up.

In the example project, the floor isn't detected at first for several frames, then it starts being detected. It stops the object from falling from the start though.

Steps to reproduce

Try the MRP with "visible collision shapes" on to be able to see anything. Run the project and see the movement of the objects in the window and the messages in the console output.

Minimal reproduction project (MRP)

collision_normal_test.zip

[AThousandShips]

See also:

• Improper collision detection at edges of trimesh collision shapes #69137
• RigidBody gets stuck on collision boundaries #46712

[berarma]

Setting the safe_margin to the lowest value 0.001 seems to be working. It still detects a collision but the calculated normal is correct and the object can keep moving along the edge.

It remains to be seen why the engine doesn't decide if it's a floor and the correct normal with a higher safe_margin.