public static CollisionResult CollidesWith(this BoundingSphereD sphere, Triangle triangle, Vector3D velocity)
{
CollisionResult collisionResult = CollisionResult.NoCollision;
/*if (!triangle.Plane.IsFrontFacingTo(velocity.Normalized()))
* {
* return CollisionResult.NoCollision;
* }*/
if (velocity.IsParallelTo(triangle.Plane))
{
if (!sphere.EmbeddedIn(triangle.Plane))
{
return(CollisionResult.NoCollision);
}
}
else
{
#region CollisionInsideTriangle
//Some precalculated variables we'll be using
double signedDistToTrianglePlane = triangle.Plane.SignedDistanceTo(sphere.Center);
double normalDotVelocity = triangle.Plane.DotNormal(velocity);
//parameters representing relative points along the velocity vector,
//therefor ranging from 0 (current position)
//to 1 (position after current velocity has been applied)
//Calculate intersection values along the velocity vector
double t0 = (-sphere.Radius - signedDistToTrianglePlane) / normalDotVelocity;
double t1 = (sphere.Radius - signedDistToTrianglePlane) / normalDotVelocity;
//Make sure t0 < t1
MathExtensions.MinMax(ref t0, ref t1);
//t1 is "less than or equal to" to prevent from being stuck when touching an object
if (t0 > 1.0d || t1 <= 0.0d)
{
//If t0-t1 is outside the range (0-1) there is no collision along the velocity vector
return(CollisionResult.NoCollision);
}
//Clamps t0 and t1 to the range (0-1), as we only care about the current frame
//in which the values represent relative points along the current velocity vector.
t0 = MathHelper.Clamp(t0, 0, 1);
t1 = MathHelper.Clamp(t1, 0, 1);
Vector3D planeIntersectionPoint =
sphere.Center - triangle.Plane.Normal * sphere.Radius + velocity * t0;
//If the intersection point is in the triangle, we have a collision.
//Since a collision with the "inside" of the triangle takes place before
//any collision with its vertices or edges, this is the closest collision,
//so we can safely return
if (triangle.ContainsPoint(planeIntersectionPoint))
{
collisionResult.FoundCollision = true;
collisionResult.IntersectionTime = t0;
collisionResult.IntersectionPoint = planeIntersectionPoint;
return(collisionResult);
}
#endregion
}
foreach (Vector3D vertex in triangle.Vertices)
{
CollisionResult vertexCollisionResult = sphere.CollidesWith(vertex, velocity);
if (vertexCollisionResult.FoundCollision &&
vertexCollisionResult.IntersectionTime < collisionResult.IntersectionTime)
{
collisionResult = vertexCollisionResult;
}
}
foreach (Edge edge in triangle.Edges)
{
CollisionResult edgeCollisionResult = sphere.CollidesWith(edge, velocity);
if (edgeCollisionResult.FoundCollision &&
edgeCollisionResult.IntersectionTime < collisionResult.IntersectionTime)
{
collisionResult = edgeCollisionResult;
}
}
return(collisionResult);
}
