public void RayCast(b2WorldRayCastWrapper callback, b2RayCastInput input)
{
b2Vec2 p1 = input.p1;
b2Vec2 p2 = input.p2;
b2Vec2 r = p2 - p1;
Debug.Assert(r.LengthSquared() > 0.0f);
r.Normalize();
// v is perpendicular to the segment.
b2Vec2 v = b2Math.b2Cross(1.0f, r);
b2Vec2 abs_v = b2Math.b2Abs(v);
// Separating axis for segment (Gino, p80).
// |dot(v, p1 - c)| > dot(|v|, h)
float maxFraction = input.maxFraction;
// Build a bounding box for the segment.
b2AABB segmentAABB = new b2AABB();
{
b2Vec2 t = p1 + maxFraction * (p2 - p1);
segmentAABB.lowerBound = b2Math.b2Min(p1, t);
segmentAABB.upperBound = b2Math.b2Max(p1, t);
}
Stack<int> stack = new Stack<int>();
stack.Push(m_root);
while (stack.Count > 0)
{
int nodeId = stack.Pop();
if (nodeId == b2TreeNode.b2_nullNode)
{
continue;
}
b2TreeNode node = m_nodes[nodeId];
if (b2Collision.b2TestOverlap(ref node.aabb, ref segmentAABB) == false)
{
continue;
}
// Separating axis for segment (Gino, p80).
// |dot(v, p1 - c)| > dot(|v|, h)
b2Vec2 c = node.aabb.GetCenter();
b2Vec2 h = node.aabb.GetExtents();
float separation = b2Math.b2Abs(b2Math.b2Dot(v, p1 - c)) - b2Math.b2Dot(abs_v, h);
if (separation > 0.0f)
{
continue;
}
if (node.IsLeaf())
{
b2RayCastInput subInput = new b2RayCastInput();
subInput.p1 = input.p1;
subInput.p2 = input.p2;
subInput.maxFraction = maxFraction;
float value = callback.RayCastCallback(subInput, nodeId);
if (value == 0.0f)
{
// The client has terminated the ray cast.
return;
}
if (value > 0.0f)
{
// Update segment bounding box.
maxFraction = value;
b2Vec2 t = p1 + maxFraction * (p2 - p1);
segmentAABB.lowerBound = b2Math.b2Min(p1, t);
segmentAABB.upperBound = b2Math.b2Max(p1, t);
}
}
else
{
stack.Push(node.child1);
stack.Push(node.child2);
}
}
}
