computeAABB method
Given a transform, compute the associated axis aligned bounding box for a child shape.
Implementation
@override
void computeAABB(AABB aabb, Transform xf, int childIndex) {
final lowerBound = aabb.lowerBound;
final upperBound = aabb.upperBound;
final xfq = xf.q;
final v1x = (xfq.cos * vertex1.x - xfq.sin * vertex1.y) + xf.p.x;
final v1y = (xfq.sin * vertex1.x + xfq.cos * vertex1.y) + xf.p.y;
final v2x = (xfq.cos * vertex2.x - xfq.sin * vertex2.y) + xf.p.x;
final v2y = (xfq.sin * vertex2.x + xfq.cos * vertex2.y) + xf.p.y;
lowerBound.x = v1x < v2x ? v1x : v2x;
lowerBound.y = v1y < v2y ? v1y : v2y;
upperBound.x = v1x > v2x ? v1x : v2x;
upperBound.y = v1y > v2y ? v1y : v2y;
lowerBound.x -= radius;
lowerBound.y -= radius;
upperBound.x += radius;
upperBound.y += radius;
}