[Radiance-dev] Mesh normals in cal files

[Mark Stock]

But won't solve the problem, though, of defining a surface 
attribute based on the normal of a smoothed mesh object. It seems 
that the only way to do this would be to try to encode the normal 
direction into the texture coordinates. Hmmm.

Mark

On Thu, 16 Jun 2005, Greg Ward wrote:

> 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
>
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