Platformer floor/ceiling collision detection flakiness

Unity Engine
1

For my platforming movement I need to keep track of two simple checks (for now):

  • If the player is standing on a block then they’re counted as on the ground and the animation changes, various flags are updated, etc
  • If the player hits their head on the ceiling then their jump is cut short early

The character itself uses a box collider with simple physics. My solution was to create head and feet trigger colliders that poke slightly out the top/bottom of the main collider and are slightly thinner, so that in theory they only collide against ceilings/floors. See diagram: Imgur: The magic of the Internet

However I find that sometimes these triggers are hitching against walls as well - i.e. I jump diagonally into a wall and sometimes the player box collider will briefly slip inside the wall’s box collider, triggering a collision on the head or feet collider and screwing up the physics.

Anybody have any idea why this happens? How do I guarantee that two box colliders will definitely never overlap at all, so I can prevent inappropriate collisions with the triggers? Or is there a smarter way to do this?

2

Since you are using trigger colliders, physics alone does not make “collisions” happen. You should check what type of collider you bumped into, usually by using tags.

3

Yeah I’m doing that, but the tag is the same whether it’s a “floor” or a “ceiling” (i.e. it could just be a floating platform). So for example if the head trigger collides with any block it will stop the jump, but I don’t want to do that unless it actually is a block above the character.

4

In the case of a jump, the vertical velocity should usually be above zero. You could check for that.