/// <summary>
/// Performs sphere-triangle intersection test.
/// Spheres can only collide with front side of triangles.
/// The closest possible intersection position is returned,
/// which is always inside the triangle.
/// </summary>
/// <param name="position"></param>
/// <param name="sphereRadius"></param>
/// <param name="result"></param>
private void TestSphereCollision(ref Vector3 position,
float sphereRadius,
ref CollisionResult result)
{
// Check side of plane
float dist;
Vector3 v = position - verts[0];
Vector3.Dot(ref v, ref faceNormal, out dist);
// Wrong side of plane
if (dist < 0)
{
return;
}
// Too far away for intersection
if (dist > sphereRadius)
{
return;
}
// Test for collision point in triangle
Vector3 collisionPoint = position - (dist * faceNormal);
if (PointInTriangle(ref collisionPoint))
{
CollisionResult t;
t.Hit = true;
t.DistanceSquared = (collisionPoint - position).LengthSquared();
t.Normal = faceNormal;
t.Location = collisionPoint;
result.KeepClosest(t);
return;
}
// Test edges
for (int i = 0; i < 3; i++)
{
Vector3 E = verts[(i + 1) % 3] - verts[i];
// Position relative to edge start
Vector3 H = collisionPoint - verts[i];
// Distance of P to edge plane
float hn = Vector3.Dot(H, edgeNormals[i]);
// Point is on same side of triangle from the edge plane
if (hn < 0.0f)
{
continue;
}
// Too far away from this edge plane
if (hn > sphereRadius)
{
return;
}
// Test intersection with polygon edge
Vector3 intersectionPoint = new Vector3();
if (SpherePartialEdgeCollide(ref position, ref verts[i], ref E, ref intersectionPoint))
{
CollisionResult t;
t.Hit = true;
t.DistanceSquared = (intersectionPoint - position).LengthSquared();
t.Normal = faceNormal;
t.Location = intersectionPoint;
result.KeepClosest(t);
}
}
}
