XNA provides a number of useful Utility classes for geometry and other applications
There are 3 vector classes Vector2, Vector3, Vector4. These classes encapsulate functionality for 2,3& 4 dimensional vectors.
Common vector functions are provided;
Vector3 a = new Vector3(1, 0, 0); Vector3 b = new Vector3(0, 1, 0); Vector3 c = new Vector3(1, 0, 1); Vector3 d; Matrix M=Matrix.Identity; float f; d = a.Add(b); // add a & b d = a.Multiply(2.0); f = Vector3.Dot(b, c); d = Vector3.Cross(b, c); f = c.Length(); f = c.Lengthsq(); d = Vector3.Lerp(a, b, 0.25); a.X = 5; a.Y = 6.7; a.Z = 2; f = Vector3.Distance(a, b); c = Vector3.Normalize(a); c = Vector3.Transform(a, M);
There is a Matrix class (representing a 4x4 matrix). This encapsulates key matrix functionality;
The Plane class contains fuctionality to work with geometric planes in 3D.
There are a number of Geometry Classes to help compute common geometry tasks