The bumpmap shader changes the normal before the surface shader is evaluated.
The surface shader then does its work which will include sampling the
lights. So if the bumpmap shader changed the normal so it was pointing
more towards the light then it would pick up light.
Though I haven't looked at this error (sorry) but if it's showing
light on an opposite face (where even a 90 degree adjustment to the
normal should not have it getting light)
Feel free to send a scene file to the laziest among us ;-)
Cheers,
Alan.
On 7/26/05, guillaume laforge <guillaume.laforge.3d(at)gmail.com> wrote:
> It seems logical to me.I don't know Mental Ray on a technical point of view
> but I imagine it works like that :
>
> With bumpmap generator, Mental ray looks at the surface level to create the
> bumpmap. So the phong do is illumination job :-) and then the bump is
> calculated on the illuminated side (given by the phong).
>
> With bump mapping in image node, Mental ray compute the bump accordingly to
> the geometry normal and then send this image to the phong shader specular
> input. So the phong "believe " that the surface normal is not completly
> "behind" .
>
> Am I correct ?
>
> Cheers
>
> Guillaume Laforge
>
> 2005/7/26, Chris Marshall <chris(at)eclipsecreative.co.uk>:
> > Hans,Veenendaal,AMplus R&D,SOJ wrote:
> >
> > >My best guess is that the default texture has very sharp bumps, that
> > >will leak rays through from the back side...
> > >
> > >Bluring the texture a bit eliminates the problem.
> > >
> > >Hans.
> > >
> > >
> > >
> > The job I'm working on is having problems with a different texture, that
> > doesn't have sharp edges.
> > I have a couple of workarounds which I'm allready using, but let's hope
> > bump maps in the next release have been 'looked at' by soft.
> >
> >
> >
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> >
>
>
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