Is it common for downloadable/purchasable models to not include material but only textures instead?

Rendering
1

I have been working with some vegetation inside Rhino lately and I noticed most models never include material files, but instead .OBJ and .MTL. The MTL is a just text file pointing to the textures (JPEGs,etc) together with some settings.

Are these settings interpreted by the Rhino Material or is Rhino simply applying a generic material with a bitmap as diffuse and bump?

2

After importing you’ll most likely see a Rhino Custom material with the textures set to the slots they belong to.

3

Hi Nathan. Right, but I wonder about the other settings. I think most are set to generic. In fact, I think the only change is gloss finish changed to 50%. Maybe other applications like 3DS MAX make use of all the settings inside the MTL file and thus have a more accurate material?

I feel like rendering a material with only a bitmap as a diffuse is not very realistic. Or maybe I just need to fiddle around with the settings. Which is alright, I just don’t know if this is always the standard workflow.

image

4

For textures it looks like we support diffuse, transparency, bump and environment (emap) textures. For colors we support diffuse, specular, ambient and transparency colors.

Are you not getting bump textures assigned where the OBJ material you’re importing is specifying one?

5

I am getting everything fine, including bump, etc. But I wonder, what happens with these numbers? Is this info lost?

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image978Ă—400 8.49 KB

I am thinking about Vray which has much more complex settings for a material such as:

image
image405Ă—653 34.8 KB

6

The specification for the MTL format is MTL OBJ materials file

These numbers are mapped to what the Rhino material knows about, but in short

  • Ns specular component. In Rhino internally shine. This is gloss in Rhino Custom material.
  • Ni optical density. In Rhino Custom material you see this as the IOR
  • d is the dissolve factor. In Rhino Custom inverted for transparency. So 1.0 means fully opaque, means 0.0 transparency
  • Tr transmission - I believe we interpret this just as the inverse of d
  • Tf transmission factor. In Rhino Custom material you see this as transparency color. I would guess in the V-Ray material you show it is Refraction color
  • illum is the illumination model. In Rhino we don’t have illumination per model
  • Ka ambient reflectivity color. I don’t think it shows in Rhino Custom material UI, but it is set to the (display) material property AmbientColor
  • Ks specular reflectivity. Rhino Custom gloss color I think
  • Kd diffuse reflectivity. Rhino Custom color
  • Ke don’t know this one, unhandled.
1 Like
7

@ShynnSup CGAxis usually have bundles dedicated for VRay if you’re after that - check the order downloads list.

8

The problem I was having with that is that VRmesh does not have materials embedded. All the rest is for MAX.