Hi Mark,

> I'm thinking that maybe the Ks is having an impact on how
> reflective the material is and how bright it looks?

Yup, that definitely sounds like the case.

But what is supposed to actually happen is that Ks is used not all by itself, but in combination with the Ns value that controls the focus size of the specular highlights.

The Ns value is an exponent, and an exponent value of 0 is a special case, setting Ns = 0 I believe should mean "specular highlights disabled", but UV Mapper does not interpret it that way.

Unfortunately there is not any great documentation available for the .mtl file format, as far as I can tell there is not any great original spec for it unlike .obj which does have a nice comprehensive original document for it.

So because of that different programs can interpret things in the .mtl slightly differently.


I'm not sure about setting Ks = 0,0,0 because that could cause someone to need to do extra work in a rendering program when they did want to enable specular highlights, because they would not only need to enable specular highlights, but also change the specular color to something other than 0,0,0 to make them show up. That may be a bit confusing to need to alter 2 settings in order to make them show up... I would need to do some experiments with a variety of other programs to see if this would happen when setting Ks = 0,0,0 or not.


You could contact the author of UVMapper and ask if he could interpret the value of Ns = 0 to mean specular highlights being disabled instead of having them turned on.


- Michael

Hi Michael,

Thanks for the explanation. I will contact the author of UV Mapper to see what can be done. For the time being what would you suggest regarding that value given that I need my models to go out to a customer using Max?

I'm glad at least that the obj format can be fixed in a text editor.

BTW, your obj merger is a wonderfully handy little tool. I can now do the same job in Simlab Composer (as promised, they have added an option to disable automatic snapping of imported objects to the scene floor) but I'm still using your tool to do the job. It is so easy to just drag the files into your tool's window and hit the generate button.

Mark

Hi Mark, so in v3 I can give setting Ks = 0,0,0 a try by default and see if it causes any difficulty.

I did a quick test, and for Blender it does mean that someone has to adjust the specular color first before adjusting the strength in order to add specularity, but Cinema4D seems to interpret it a bit nicer and just has specular color disabled (and implicitly white) and still can enable specular highlights more easily.

Each program can interpret these things in a slightly different way.


> For the time being what would you suggest regarding that
> value given that I need my models to go out to a customer
> using Max?

Well, I guess if you don't want any specularity the safest thing is to set Ks = 0,0,0 in addition to Ns = 0, that seems to have the best chance of having it turned off in a receiving application.

But since each program interprets this slightly differently it is hard to really know for sure what Max is going to do with it without actually testing it.

- Michael

Hi Michael,

Perhaps make those settings an ini thing and mention in the V3 docs that some apps interpret this differently and how to go about addressing it? I can see needing to turn specularity back on would be a real pain for most users as they are going to be rendering out their own models in the renderers they own. I understand better what the issue is now and really, fixing it using a text editor is not a problem.

Thanks for the help Michael.