Re: AW: Reflections..

[André Adam <a_adam(at)49games.de>]

If you mean the reflection issue, that's rather quickly explained, to 
calculate reflection (as well as highlights and shading, btw) the 
surface's normals are evaluated to determine the surface's direction, 
which of course is needed to find out what's reflecting on this surface 
from the current point of view.
Now, since we're dealing with triangles that are only an approximation 
of a real surface, the limited information of the vertex normals gets 
interpolated across the polygons. The distortions are caused by a too 
broad approximation of the modelled topology relative to what it is 
meant be.
In Martin's example I guess the hole in the middle of the geometry is 
causing the problems where the unified vertex normals around the hole 
get bent towards the hole's center, therefore distorting the 
interpolated normals on the main surface.
The quickest workaround is to create hard edges to break up the normals 
so that all normals contributing to the main-surface's normals point in 
the very same direction.
A better fix would be to create more geometry at the right places to get 
a better triangle approximation of the real-life surface he is trying to 
simulate.

Hope that helps and makes sense! Cheers!

   -André

Xsiberger wrote:

> I also would appreciate any link/book which describes the theory behind this
> phenomenon. is it called surface discontinuity? google didn't deliver
> something usefull to this subject.
>
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] Im Auftrag von
> Martin Belleau
> Gesendet: Freitag, 2. Juni 2006 16:27
> An: XSI(at)Softimage.COM
> Betreff: RE: Reflections..
>
> Just like few people understand the concept of scene optimization. What's
> clean and what isn't.
>
> Do you have a link so I can read up on this (normals)?
>
> -----Original Message-----
> From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf Of
> kim aldis
> Sent: Saturday, June 03, 2006 1:06 AM
> To: XSI(at)Softimage.COM
> Subject: RE: Reflections..
>
> It's to do with the way normals are calculated on points by averaging plane
> normals of contributing faces.  If you have a think about how this works it
> starts to make sense.
>
> An understanding of how shading works and how normals are built is
> fundamental to good poly modeling and it always surprises me how few people
> understand it.
>
> Chris, you still have your beveled cube thing kicking around?
>
>
> -----Original Message-----
> From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf Of
> Martin Belleau
> Sent: 02 June 2006 14:37
> To: XSI(at)Softimage.COM
> Subject: RE: Reflections..
>
> Oki it works much better... But what happens if I don't want to use hard
> edge, and use a Bevel... 
>
>
>
>
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