// test collision between two spheres
public static bool TestSphereSphere(Transform a, Transform b)
{
// if the distance between their centers is less than the sum of their radii
// return true (i.e. is colliding)
// else return false (i.e. is not colliding)
return ((a.Position - b.Position).Length() < (a.Scale + b.Scale).Y);
}
// Default Constructor
public Transform()
{
Position = Vector3.Zero;
Scale = Vector3.One;
Rotation = Quaternion.Identity;
Children = new List<Transform>();
parent = null;
}
public static bool TestSphereTriangle(Transform sphere, Vector3 a, Vector3 b, Vector3 c, Vector3 normal)
{
// Find the separation distance between the sphere center and the triangle plane
float separation = Vector3.Dot(sphere.Position - a, normal);
// If the separation value is out of bounds, quit
if ((separation > sphere.Scale.Y) || (separation < 0))
{
return false;
}
else // Otherwise, there is collision with the plane. Find the nearest point
{
Vector3 pointOnPlane = sphere.Position - normal * separation;
// Find the barycentric coordinates
float area1 = Vector3.Dot(Vector3.Cross(b - a, pointOnPlane - a), normal);
float area2 = Vector3.Dot(Vector3.Cross(c - b, pointOnPlane - b), normal);
float area3 = Vector3.Dot(Vector3.Cross(a - c, pointOnPlane - c), normal);
return !((area1 < 0) || (area2 < 0) || (area3 < 0));
}
}
// test collision between a sphere and a triangle given as three vectors (i.e. lines)
public static bool TestSphereTriangle(Transform sphere, Vector3 a, Vector3 b, Vector3 c)
{
Vector3 normal = Vector3.Normalize(Vector3.Cross(b - a, c - a));
return TestSphereTriangle(sphere, a, b, c, normal);
}
// test collision between a sphere and a triangle
public static bool TestSphereTriangle(Transform sphere, Triangle triangle)
{
return TestSphereTriangle(sphere, triangle.a, triangle.b, triangle.c);
}
