Quadtrees and collision detection
A quadtree for organizing points and finding nearby objects.
Partitioning a scene
PointQuadtree stores one point at each node and splits the remaining rectangle into four quadrants around that point. Insertion follows the matching quadrant recursively, preserving the spatial bounds at every child.
Circle queries
A proximity query first checks whether its circle intersects a node's rectangle. It only recurses into intersecting quadrants, then tests the node's point against the circle. This avoids examining every point for a local search.
Two interfaces
DotTreeGUI supports adding points and querying nearby points with the mouse. CollisionGUI puts MovingPoint instances in a quadtree on each timer update, finds overlapping circles, and can either color or remove the colliders.
