Objective

Contact pair removal currently has some issues.

1. Contact pair removal is done using the EdgeIndex directly, but removing an edge can move the indices around (due to swap_remove), which can sometimes result in incorrect pair removal if many pairs are removed at once.
2. Changing CollisionLayers doesn't update existing contact pairs.
3. When a collider is removed or disabled, CollisionEnded is sent even for non-touching contact pairs.

Solution

Fix the things!

For problem 2, I just made the narrow phase always check if the CollisionLayers match for now. Ideally, we'd handle this with fine-grained change detection instead.

CollisionLayers is now also a required component for colliders. This avoids extra branching and is perhaps more semantically accurate; colliders can only belong to collision layers if they have the component for it.

Migration Guide

CollisionLayers is now a required component for colliders.