NeoAxis 3D Engine is versatile 3D project development environment. The environment can be used to develop all kinds of 3D projects such as computer games, visual trainers, VR systems, to visualize processes and develop windowed applications. The framework can be efficiently used in educational institutions as a tool to develop cutting edge 3D graphics skills.
Caelum is an add-on to the OGRE Graphics Engine, which simulates an atmospheric sky with a sun. For more detail visit this post on Ogre's forum. Unfortunately, Caelum is written in C and then it can't be integrated with NeoAxis Engine. So we developed Caelum for NeoAxis which is a Caelum's translation in C# and which is specially conceived for NeoAxis.