[Radiance-general] Ambient exclude transfomed material in instances

[iebele]

Thanks Greg an Jack for your excellent and very  helpfull suggestions.

I now have succesfully converted the .obj file to rad, using obj2rad ( 
polytrans did indeed work with Xfrog obj-files, but meshlab did not 
accept these files Lars ).

However I can't get the mapping right. I've tried a lot, but with no 
succes. Would you please share with me an example of the materials you 
use for the bark and the leaves?

I just don't really understand when and how to use Lu and Lv  or 
frac(Lu) and frac(Lv) in the colorpict modifier and how these can ever 
be placed  in a reasonable way on each triangle in the output of 
obj2rad, which in my case is like :

leaf_col_leaf2 polygon leaf22836.60976
0
0
9
         -0.250204           0.195593             13.838
          -1.00383          -0.956752            13.8816
          -1.21881           -0.19178            13.5622

I never really understood the meaning of texture-coordinates, but at 
this time I feel that is what  is  missing here.

Is there a difference in using obj2rad and obj2mesh for this purpose ? I 
tried both but with the some odd results concerning the coordinate mapping.

-Iebele

Jack de Valpine wrote:

> Hi Greg and Iebele,
>
> I have a comment and a question on this.
>
> First, Iebele, I have also just gotten a 3D xfrog tree. FYI, it is 
> possible to generate an obj, convert to a radiance mesh and use Local 
> u,v coordinate mapping to get the leaf and bark materials to apply. I 
> have a tree right now that basically has a few materials defined for it:
>
>    1. bark with colorpict modifier
>    2. leaf with colorpict modifier
>    3. leaf-mix mixpict - this uses an alpha version of the leaf to mix
>       between void (ie where the alpha is black) and the leaf material (2)
>
> The question for Greg is this, to exclude the leaves from the ambient 
> calculation what needs to be listed in the exclude file the "leaf" 
> material and/or the "leaf-mix" material?
>
> Iebele, the one thing to note is that the obj file that comes out of 
> xfrog does not play well with obj2mesh or obj2rad. Thus I have to 
> bring it into PolyTrans and re-export as an obj to get a file that 
> radiance is happy with.
>
> Best,
>
> -Jack
>