fix method
Fix the dynamic bounding volume of the input node
Implementation
void fix(DBVTNode node){
DBVTNode c1 = node.child1!;
DBVTNode c2 = node.child2!;
node.aabb.combine( c1.aabb, c2.aabb );
node.height = c1.height < c2.height ? c2.height+1 : c1.height+1;
}