/**
* March through Octree checking collisions. Every node on the way (when traversing to leaf direction) is checked for hits.
*
* @param v point to search for
* @param c collision details
* @return smallest node containing v, or null if (and only if) v is not inside the tree
*/
public Node MarchToCheckingCollisions(Vect3 v, CollisionDetails c, Shapes.Ray ray)
{
if (Encloses(v))
{
if (_child == null)
{
return(this);
}
foreach (Node n in _child)
{
if (n.Encloses(v))
{
c.CheckCollisionSet(n.Content, ray);
return(n.MarchToCheckingCollisions(v, c, ray));
}
}
return(this);
}
if (_parent != null)
{
return(_parent.MarchToCheckingCollisions(v, c, ray));
}
return(null);
}
public static CollisionDetails GetFirstCollision(Octree tree, Shapes.Ray r)
{
var c = new CollisionDetails {
Distance = double.PositiveInfinity
};
double distanceTravelled = 0; //distance traveled since the ray's origin
//Algorithm starts at the ray's origin and in the root node.
Node n = tree.GetRoot();
c.CheckCollisionSet(n.Content, r);
var pos = r.Origin;
if (!n.Encloses(pos))
{
throw new Exception("Ray's origin is not located in the octree!");
}
do
{
//March to the leaf containing "pos" and check collisions
n = n.MarchToCheckingCollisions(pos, c, r);
//No leaf is containing "pos" -> left tree -> stop searching
if (n == null)
{
break;
}
//march out of current node
double d = RayCube.GetDistanceToBorderPlane(pos, r.Direction, n.Center, n.Width / 2) + Constants.EPS * 1e4;
//distance traveled since the ray's origin
pos = pos + r.Direction * d;
distanceTravelled += d;
//in case eps was not enough
while (n.Encloses(pos))
{
d = Constants.EPS * 1e4;
pos = pos + r.Direction * d;
distanceTravelled += d;
}
/**
* When passing a box-border, all intersection tests between the ray's origin and the
* box-border-intersection-point must have taken place (and some beyond the box-border too).
* Therefore, if an intersection located between the ray's origin and the box-border has been found, this
* must be the nearest intersection and the search may stop.
*/
} while (c.Distance > distanceTravelled);
return(c);
}
private CollisionDetails GetFirstCollisionInternal(Shapes.Ray ray, bool isRayInside, bool useBiggerX, bool useBiggerY, bool useBiggerZ)
{
var result = new CollisionDetails {
Distance = double.PositiveInfinity
};
if (isRayInside) // recheck because ray was inside parent
{
isRayInside = PointCube.Encloses(_center, _halfWidth, ray.Origin);
}
// not inside and no hit -> return
if (!isRayInside && double.IsInfinity(RayIntersectionDistance(ray, useBiggerX, useBiggerY, useBiggerZ)))
{
return(result);
}
if (_children != null && _children.Length > 0)
{
foreach (var child in _children)
{
var collision = child.GetFirstCollisionInternal(ray, isRayInside, useBiggerX, useBiggerY, useBiggerZ);
if (!double.IsInfinity(collision.Distance))
{
result = collision;
break;
}
}
}
foreach (var o3D in _objects)
{
double distance = o3D.GetHitPointDistance(ray);
if (distance > 0 && distance < result.Distance)
{
result.Obj = o3D;
result.Distance = distance;
}
}
return(result);
}
