Accessing an OBJ file's Texture Filename

[Andrew Davison]

When ObjectFile is used to load an OBJ file, its MTL file, and a texture, there seems to be no way to access the texture's filename by examining the scenegraph that's created.

Other MTL settings, such as Ka, Kd, are accessible through Material, but not the map_Kd value.

I could parse the OBJ file and its MTL file myself, but the texture filename should really be in the scenegraph for easier access.

- Andrew