The mesh viewer tool is used to process exported xsi files from a 3D modeling package into the binary god file format that is loaded by the DR2 engine. It also has quite a few features that are helpful for debugging art assets. There might seem like a lot of buttons and sliders, but just follow the step-by-step guide to producing god files to get started.
Art Creation Guidelines
General guidelines for creating art resources for use in Dark Reign 2.
God Files
Quick guide to creating binary god files from xsi and x files in the Mesh
Viewer..
Hot Keys
Key command reference.