[Radiance-dev] Mesh normals in cal files

[Greg Ward]

Hi Mark,

Just like a tessellated surface, a mesh in Radiance is represented as  
the individual polygons and the Nx, Ny, Nz, and Rdot variables  
correspond to the actual "unperturbed" surface normals.  The only  
time the perturbed values are known is during material evaluation,  
which is why plastic comes out looking smooth.  If you want to play  
with the perturbed value, you'll have to utilize the NxP, NyP, NzP,  
and RdotP variables that are available from the brdf primitives.

-Greg

> From: Mark Stock <mstock at umich.edu>
> Date: June 16, 2005 6:01:40 AM PDT
>
> I just noticed that the perturbed mesh normal is unavailable in  
> the .cal file language. Is that an oversight, or a major difficulty?
>
> When I use the following code, my mesh appears very triangulated,  
> but when I use "void plastic def" it appears smooth.
>
> Mark
>
> ---------
> {
>   brighten_normal.cal
>   make a surface brighter if the normal faces the viewer
> }
>
> br = Rdot*Rdot;
>
> ---------
> void brightfunc surffunc
> 2 br brighten_normal.cal
> 0
> 0
>
> surffunc plastic def
> 0
> 0
> 5  0.14 0.07 0.07  0.0 0.0
>
> def mesh theblob
> 13 smoothed.msh -t 0 0 -1.75 -rx 180 -rz 45 -rx -35 -rz 30
> 0
> 0