BaseParts on terrain do not collide as expected

[Maelstronomer]

While rolling a sphere (or dropping a part onto terrain) the part will bounce randomly.

This causes issues particularly for vehicles that rely on stability from ground connections.

System information: Windows 10

Reproduction file: (“Run”, instead of “Test” so you can see them drop)
ball drop test.rbxl (61.0 KB)

Expected behavior

I am expecting no random variance upon dropping/rolling across the surface of terrain; especially flat terrain.

[calternitive (Calturn)]

Since the terrain’s physics body is calculated differently than a box shape physics body, it can vary. I’m guessing Terrain collisions have weirder triangles than a box’s physics body. Maybe physics properties could also possibly interfere

[Maelstronomer]

This phenomenon actually happens with regular BaseParts too, like when you have two flat parts together and the object lands on the invisible “seam” between them.

The previous physics engine didn’t have the unexpected behavior. ):

[calternitive (Calturn)]

Yeah, its probably an internal bug. My best guess is that it calculates it weirdly when it reaches the seam like you said. Terrain also probably does this A LOT, wood terrain has a lot of edge vertices when you peek at the wireframe.