What is this?
Nexus is a 3D maths library for .NET and Silverlight. It has no dependencies. It is intended for use in situations where you don't want to install heavyweight frameworks, such as XNA. There is also a build available for Silverlight.
Nexus uses a mixture of XNA and WPF conventions. For example, it uses separate structures for Point3D and Vector3D (same as WPF) but it also includes code for bounding boxes, frustums, and planes, which are not included in WPF.