OTOY Forums

Hi,
Recently I have been tinkering with Solidworks API to write out .obj from parts,assemblies. In the course of that I have been looking at what happens to the .obj materials when it is imported into Blender, worked on and then exported to Octane, and also what happens when the SW.obj materials are used directly by Octane from SWX.
Presently some of the .mtl parameters are not used by Octane or how they are interpreted is not so helpful.
Here is what we (Refractive) might do.

Ka - is not used at all. XXXX
Kd - used by Octane for Specular-Transmission, Glossy-Specular and Diffuse-Diffuse colours.
Ks - used by Octane for Specular colour, if zero flags a Octane Diffuse mat otherwise its a Specular mat. Conversion is scaled in the preferences setting.
d - currently not used but could be used for Opacity, same range 0-1.
Ns - used by Octane for Diffuse mat and Glossy mat Roughness (but not for Spec mat bug?) but with a strange scale conversion, should be 1000-0 > 0-1.
Ni - used by Octane for IOR, if 1.0 then it flags an Octane Glossy mat.
Tf - currently not used but could be used for Medium Absorbtion (sss) colour if RGB.
illum - currently not used but could use for flagging transparency ie use a Octane Specular mat, and also for flagging Octane Diffuse and Glossy mats.

I realise some of the eqivalent parameters for texture maps are supported already but for mats conversion is incomplete or unhelpful/inconvenient.
The trouble I have is basically with the Glossy and Spec flags upsetting conversions between programs.
I would rather flag a Spec mat by the illum parameter. While SWX delivers a value for Ni it can't be set just using the usual 'Appearances' interface. This means all mats arriving in Octane are specular by default rather than glossy.
The obj specification says illum 4,6,7,9 involve transparency but illum 7 would be handiest for Blender round trip since it has mirror, fresnel and raytrace (as opposed to z transparency).
If illum 2 was used the imported mat would be a Glossy mat. Diffuse mats would be flagged by illum 1.
Really I suppose I am asking for alternative flags rather than replacements.

So any thoughts from the community about using d for Opacity, Tf for sss, fixing the Roughness, and alternatively illum 1,2,7 for Diffuse, Glossy and Specular respectively?

pixelrush wrote:So any thoughts from the community about using d for Opacity, Tf for sss, fixing the Roughness, and alternatively illum 1,2,7 for Diffuse, Glossy and Specular respectively?

When I know I will render something (only) with Octane, I don't bother to set up material parameters in Blender at all. It's impossible to do a proper conversion and for a lot of shader parameters you can't see how it will change the appearance in Octane - so it's useless to blindly tweak them in the 3D app. I don't really care how Octane interprets those params., because I do all my material settings in Octane.

I would be more interested if RS would code an expanded format, with such possibilities like multiple UV coordinate sets per object (when Octane will know about objects), for example.

But some people do use the exporter to tweak their materials and might find this useful (the conversion can be OK for simple materials). Also, the .obj format is already limited as it is, so I think Octane should take every bit of info that can be sent to it.

Yeah I realise mats conversion is difficult however what I would like is to be in the ballpark so it is tweaking rather than changes everywhere.
In the case of SWX the usual interface for applying 'Appearances' has different options from what is available from the GetMaterials vb that the .obj+.mtl can draw on, and what is available for official renderers like Photoworks, Photo360 or Maxwell is different again.
I ought to be able to set a material type, colour and basic parameters and have that transferred pretty much the same. ATM I find I have to go through everything again which is very inefficient.
I'd like a glossy blue to be a glossy blue rather than specular with bluish tints and strange roughness.
Remember we are talking about product and machinery viz with SWX rather than tree bark, butterflies etc.

1000th post

pixelrush wrote:
1000th post

Congratulation
ciao beppe