The wavefront format (.obj and .mtl) is one of is one of the most straightforward format for Sketchfab. But matching the materials and getting the expected results is not always obvious.
Materials
Materials in a material wavefront file are directly related to a Sketchfab material.
newmtl material_0
Channels
A material contains one or more parameters. Some of them are supported by Sketchfab and can be directly bound from the wavefront format to Sketchfab’s material editor. Most of them accept either a color or a texture (prefixed withmap_).
Colors are Red-Green-Blue float values inside the range [0-1].
Accepted texture file formats are jpg, tiff, dds and png (for alpha transparency).
Diffuse
Kd 1 0 0
map_Kd diffuse.jpg
The diffuse color as in phong illumination model is the color of a lit object.
Specular Color
Ks 0 1 0
map_Ks specular.jpg
Color of the lighting highlights.
Shininess
Ns 42
map_Ns shininess.jpg
Specular shininess : the lower, the shinier. Texture should be greyscale levels of shininess.
Bump / Normal Map
map_bump bump.jpg
map_normal normal.png
Simulates lighting and make bump details on the surface of an object without actually modifying its shape. Accepts only textures used as bump (greyscale heightmap) or normal map (bluish texture).
Opacity
d 1
map_d transp.png
Makes an object transparent. Overlapping transparent surfaces should be split into different objects for better results. More details about this here.
Emission
Ka 0 0 0
map_Ka ambient.jpg
Colorizes and textures an object disregarding lights.
Notes
Currently objects sharing the same material are merged into one object.
Also duplicate materials (which have the same values) are merged into one material. This behaviour could cause difficulties making separate objects, and will be reworked soon.
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