# Export Wavefront .mtl file -- Where is the reflectance coefficient?

It seems that when exporting a model, the output .mtl file does not include reflectance coefficient, which in blender is set using under "Mirror" in "Material".

The .mtl file is as follow:

# Blender MTL File: 'None'
# Material Count: 1

newmtl Material
Ns 96.078431
Ka 0.000000 0.000000 0.000000
Kd 0.640000 0.640000 0.640000
Ks 0.500000 0.500000 0.500000
Ni 1.000000
d 1.000000
illum 2


Is there a way to include reflectance in this file?

I'm not sure this is directly related to Blender, or Blender's .obj exporter. The wavefront file description mentions a set of 11 illumination models (from 0 to 10), none of which seem to specify explicitly any coefficient for reflection, merely that there is reflection:

Multiple illumination models are available, per material. These are enumerated as follows:

0. Color on and Ambient off
1. Color on and Ambient on
2. Highlight on
3. Reflection on and Ray trace on
4. Transparency: Glass on, Reflection: Ray trace on
5. Reflection: Fresnel on and Ray trace on
6. Transparency: Refraction on, Reflection: Fresnel off and Ray trace on
7. Transparency: Refraction on, Reflection: Fresnel on and Ray trace on
8. Reflection on and Ray trace off
9. Transparency: Glass on, Reflection: Ray trace off
10. Casts shadows onto invisible surfaces

• Blender makes a distinction between specular reflection from lights and mirror reflection. In reality they are the same thing, and the OBJ file format also does not make any distinction, it has only one Ks value. Sep 16 '13 at 22:51
• The way to actually specify the illumination model in the MTL file is by illum <MODEL> Feb 23 '15 at 16:35