[Radiance-general] strange artifacts

[Gregory J. Ward]

Hi Francesco,

This could be a problem with obj2mesh, though at first glance I can't  
spot anything wrong with the code.  Is it possible that whatever  
software is generating the OBJ is being clever and not including  
surface normals on the flat quad vertices?  Say it was including  
surface normals on the vertices next to the edge, where it needs  
them, but not on the interior vertices, which should match the  
geometric surface normals.  In such a case, I could understand why  
obj2mesh would screw up as it converted quads to triangles, some of  
which would have surface normals and others which wouldn't.  Where  
such triangles shared an edge, you would end up with inconsistent  
output like this.

It may be fixable, but I need to get a copy of your OBJ file to study  
it.  Send it to me gzip'ped in a separate e-mail.  (No need to copy  
the group.)

-Greg

P.S.  Out of curiosity, do you get the same results from obj2rad?

> From: Francesco Anselmo <pisuke at blueyonder.co.uk>
> Date: June 27, 2005 7:37:08 PM BDT
>
> Hi all!
>
> I'm experiencing a strange problem:
> http://www.bozzograo.net/radiance/pub/artifacts.jpg
>
> I'm exporting the model of a curved glass with vertex normals
> to obj and converting it into a radiance mesh.
> I'm using the dielectric material with it, so the glass object has two
> surfaces (inner and outer side of glass), but I can't get rid of this
> strange effects at the edges, where the quads become triangles.
>
> The remaining part of the surface is fine, even at the center,
> where there are some other triangles. I need to subdivide the polygons
> many time before this effect becomes less noticeable ...
>
> Any ideas?
>
> Thanks!
> -- 
> Francesco
>