Alain <ele### [at] netscapenet> wrote:
> gadoid nous apporta ses lumieres en ce 2007/09/06 23:44:
> > Alain <ele### [at] netscapenet> wrote:
> >> gadoid nous apporta ses lumieres en ce 2007/09/06 22:23:
> >>> "Trevor G Quayle" <Tin### [at] hotmailcom> wrote:
> >>>> "gadoid" <hansen at tkgate.org> wrote:
> >>>> ....
> >>>>
> >>>> I may have narrowed the problem down for you.  It appears to be affected
> >>>> ultimately by the size of the normals of the plane behind the spheres.
> >>>>
> >>>> Try removing the plane normal or making it smaller and see what happens.  It
> >>>> doesn't matter what normal type you have on the spheres, so it's not related
> >>>> to the crackle pattern.  Whatever is causing it, the normals on the plane
> >>>> appear to be getting reversed by the spheres.  For example try rendering
> >>>> with "bozo 4" normal on the plane and then "bozo -4" and compare.
> >>>>
> >>>> Hope this can help someone track down the reason or bug causing it.
> >>>>
> >>>> -tgq
> >>> I did notice the problem only happens when the surface beyond has a normal.
> >>> You are right that it may be reversing the normal, I at first thought it was
> >>> just shifting it.  I'm beginning to think that this must be a POV-Ray bug,
> >>> but if it is, I need to find a work-around for my scene.  I can't get rid
> >>> of the "normal" on the surface behind the object, because that is water and
> >>> I am using the normal to generate the waves.  I have hundreds of the
> >>> "electron" objects in the scene.  The only thing I can think of is to
> >>> #declare a different object for every orientation I need since the
> >>> unrotated objects seem to render fine.
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >> Don't rotate the texture! Instead, create the objects at the origin, rotate the
> >> objects, thanslate them to the final position. As you are using spheres,
> >> rotating the object or the texture will wave the same final aspect, minus the
> >> normal alteration.
> >>
> >> In my tests, the effect depends on the axis of rotation relative to the
> >> camera-object vector. An object with a z rotation just in front of the default
> >> camera show no effect, while the same object shifted up/down or lateraly will
> >> exibit the effect.
> >>
> >> --
> >> Alain
> >> -------------------------------------------------
> >> When you don’t know what to do, walk fast and look worried.
> >
> > Unfortunately, I still get the problem when I rotate the object and not the
> > texture.  I was rotating the texture because in an earlier scene, I was
> > using a gradient with turbulence to get rings of lightning, and I wanted
> > them to have different orientations for the different instances of the
> > object.  Ultimately, the sphere will have legs and thus will not be truly
> > symmetrical.  I've since decided to use crackle to get lightning so I don't
> > really need to rotate the texture anymore, but rotating the object still has
> > the same problem.
> >
> > I'm not seeing any difference in the effect irregardless of where I put the
> > camera.  The unrotated sphere at <-0.5,1,0> is invisible no matter where I
> > put the location and look_at.  How are you getting it to appear?
> >
> >
> If you don't rotate the sphere, it's placement is irrevelent. IF you rotate the
> texture, THEN the location DOES have an effect. If the axis of rotation is
> parallel to the camera-object axis, then you don't have the problem.
>

I see said the blind man.  I didn't try that, or at least I wasn't paying
close attention to the rotated spheres while looking at the non-rotated
one.

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