Is loading .obj file with .mtl files still supported?

[leleju]

In mitsuba documentation 0.5.0, it states that obj files .mtl files can be automatically loaded. I currently have a obj file where some parts of it are red and some parts are blue (all using the simplest diffuse model). I opened the obj file with windows 3d viewer and it looks fine.

However, if I simply add the obj in mitsuba as:

<shape type="obj" id="myshape">
    <string name="filename" value="myshape.obj"/>
</shape>

Then it renders the whole obj as a gray diffuse surface. If I do the same thing as stated in the documentation:

<shape type="obj">
    <string name="filename" value="myShape.obj"/>
    <bsdf name="Glass" type="dielectric">
          <float name="intIOR" value="1.5"/>
    </bsdf>
    <bsdf name="Water" type="dielectric">
          <float name="intIOR" value="1.333"/>
    </bsdf>
</shape>

then I get the error that each obj can only be assigned with a single bsdf. Does that mean that I need to divide my obj files into parts, and assign a different bsdf to each one instead of simply using the .mtl file?

I'm currently using python 3.12 and mitsuba 3.5.

[merlinND]

Hello @leleju,

Indeed, Mitsuba 3 does not account for the .mtl files. The recommended workflow to create scenes is to use the mitsuba-blender Blender add-on, which will automatically split meshes by material and export a correct XML file.

Pull requests adding support for MTL files may be welcome (@wjakob and @njroussel to confirm?).