StarCraft II models use the
.m3 file extension. This is the next version of the MDX format lineup, succeeding World of Warcraft's
Currently the only way to convert your models into .m3 is to use NiNtoxicated01's 3D Studio Max Plugin. As the name implies, the plug-in requires 3D Studio Max. The trial version of 3D Studio Max can be downloaded here.
The .m3 format uses triangular polygons. It also supports several mapping styles: diffuse mapping (color), normal mapping (detail), specular mapping (shine), and emissive/luminance mapping (glow). The maps and texture files in general are .dds images.
Diffuse mapping is the model's basic color. Specular mapping adds shine to the model, and is generally used for sweaty skin, metallic gleams, simulated reflections, and related purposes. Emissive/luminance mapping is used for glowing surfaces; such surfaces are common on Protoss units and buildings.
There is an external .m3 viewer available here.
Stante's Blender .m3 Plugin is here.
NiNtoxicated01's 3D Studio Max Plugin is here.
GalaxyEdit has a built-in .m3 viewer, which you get to by going to Window->Previewer, then choosing an asset such as unit, and pressing load.