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