MTL Node setup? Tweet

[voon]

Importing OBJ with MTL creates the meshes and material names .. but no nodes. I have to painfully recreate manually everything in the MTL. Is it possible to have this automated somehow? So that it also creates materials with the glossy shader, using the spec, diff etc maps specified in MTL files?

[grimm]

This is an issue with Blender. Blender doesn't have a good way to convert nodes to mtl as it's not straightforward to do so. The plugin uses the same node system that Cycles uses so it has the same limitations. It's also a limitation of the mtl (obj) format which doesn't understand nodes. I think we are moving past obj as a viable format and it's showing it's age a lot.

[voon]

Hm .... how would a material like this translate to Blender or Octane then:

newmtl dark_metals
Ka 0.191202 0.191202 0.191202
Kd 0.191202 0.191202 0.191202
Ks 0.027321 0.027321 0.027321
Ns 0.498039
d 1.000000
illum 2
map_Kd objects\spaceships\ships\aegs\retaliator\textures\dark_metals_diff.dds
map_bump objects\spaceships\ships\aegs\retaliator\textures\dark_metals_ddna.dds
decal objects\spaceships\ships\aegs\retaliator\textures\dark_metals_diff.dds
map_Ns objects\spaceships\ships\aegs\retaliator\textures\dark_metals_spec.dds
map_d objects\spaceships\ships\aegs\retaliator\textures\dark_metals_blnd_diff.dds

I'm confused by the required setup.

Kd seems to be the diffuse texture for a glossy shader.
map_bump seems to be the colored normal map
map_Ns seems to be the specmap for the specular input

But I don't understand a second texture decal and the "blend" texture map_d

And what's with the color definitions in the header (Ka, Kd, Ks), if textures are being used? It seems MTL assumes some kind of mixing is going on, but even after reading various MTL references, I didn't quite get it :/ I assume it's some kind of mix texture / mix material, controlled by the map_d for mixing or something. But map_Kd and decal reference even the same map (is this just a lazy MTL file or does this actually make any sense?). In other cases, there's two bump lines in a material etc. Not sure if I'm suppsoed to mix those to feed them into the normal input in octane.

Actually, is there a document easily explaining how you would create an Octane material, starting with an MTL description? I have a real hard time googling one.