I don't know how you can extend Nuclear Fusion / Nuclear Basic, so you'll have to refer to the documentation of this engine.
However, there is a phase that is always the same: the creation of a SPK::Renderer. For the moment, there are a few renderers, all in C++ (SPARK version between brackets):
- Native OpenGL (1.x - 2.0svn)
- Irrlicht (1.x - 2.0svn)
- Native DirectX (1.x, might work with 2.0)
- SMFL 1.4 (1.0, we're waiting for SFML 2 to port it to SPARK2)
- DarkBASIC Pro (a wrapper of the native DirectX renderer I think)
Just open the sources of these renderers to see how they're made (src/Rendering and include/Rendering).