Alain <aze### [at] qwertygov> wrote:
> Danny nous apporta ses lumieres ainsi en ce 2004/05/18 15:08... :
>
> >"Danny" <danzaetz> wrote:
> >
> >
> >>Alain <aze### [at] qwertygov> wrote:
> >>
> >>
> >>>Danny nous apporta ses lumieres ainsi en ce 2004/05/17 16:39... :
> >>>
> >>>
> >>>
> >>>>Alain <aze### [at] qwertygov> wrote:
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>Danny nous apporta ses lumieres ainsi en ce 2004/05/17 05:23... :
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>>Alain <aze### [at] qwertygov> wrote:
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>I used exactly what you told me, and I got a cylinder with white edges that
> >>>>>>fades to nothing in the middle (without any red at all), and even those
> >>>>>>white edges disappear as the cylinder continues on.  I'm using POV-Ray 3.5,
> >>>>>>and here is the code I used:
> >>>>>>
> >>>>>>cylinder{<100,0,0>,<0,0,0>, .20
> >>>>>>       texture {
> >>>>>>  pigment { color rgbt 1}
> >>>>>>  finish{reflection 0}}
> >>>>>>     interior{media{emission rgb 1
> >>>>>>     density{ cylindrical
> >>>>>>     color_map{[0 rgb 0][0.5 rgb<1,0,0>][0.98 rgb 1][1 rgb 2]}
> >>>>>>     }}}
> >>>>>>     hollow
> >>>>>>     translate<0,0,2>
> >>>>>>     }
> >>>>>>
> >>>>>>Can you tell me what I'm doing wrong, and how to fix it?
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>Set the radius of the cylinder to 1, then rescale it by scale<.2,1,.2>
> >>>>>just before you rotate it.
> >>>>>You don't need to set finish{reflection 0}}, it's the default value.
> >>>>>Set your cylinder verticaly, as it's the orientation of the cylindrical
> >>>>>pattern, then rotate the whole thing.
> >>>>>...
> >>>>>scale<0.2, 1, 0.2>
> >>>>>rotate -90*z
> >>>>>translate<0, 0, 2>
> >>>>>}// that's the last brace
> >>>>>
> >>>>>Alain
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>OK, now it looks good when I don't scale it, but scaling it seems to mess it
> >>>>up.
> >>>>When I scale it up it still seems to look OK, except the inner white part
> >>>>has become enlarged disproportionately.  But when I scale it down, I lose
> >>>>the white part completely, and all I have is a very dimly red cylinder.
> >>>>Can you explain why it's doing this and how I can make it scale down right?
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>Try lowering the 0.98 to a smaler value, thus enlarging the central
> >>>part. As it is now, the white center part only have a radius of 0.02
> >>>units and may disappears when scaled down or if the image is generated
> >>>at a low resolution.
> >>>Don't scale only the media but the whole cylinder containing the media.
> >>>
> >>>Alain
> >>>
> >>>
> >>Thanks a lot for all your help!  I managed to fix the scaling problem by
> >>multiplying the brightness of all the color map values by 5.  I guess this
> >>is because there is less matter in the media to show up if I scale it down
> >>to a fifth of its size.
> >>
> >>
> Good guess
>
> >>Thanks,
> >>Danny
> >>
> >>
> >
> >I've got another problem. For some strange reason, my media cylinder is
> >acting like a convex lens. It's showing an narrowed image on the right side
> >of the cylinder of an object behind and to the left of it.  It's refracting
> >(not reflecting) light, I think.  When I zoom out, it looks like ugly white
> >lines on the side of my laser. How do I get rid of them?
> >
> >Danny
> >
> >
> >
> With emissive only media, the beam is effectively transparent, that is,
> you see anything that may be behind. That was (barely) visible in the
> small sample as a slight discontuity near the middle of the image. You
> may want to add some absorbtion and/or scattering, it's not realistic as
> the beam is only light, but may be more aestetic.
>
> Alain

Neither the absorption nor any of the scatterings are able to get rid of the
image.  It's odd.  It's not like the stars I have in the distance, which
are right behind the the laser and are completely visible through the
laser.  The object is not directly behind the laser, it's back and to the
left, and not obstructed by the laser at all, but it's projecting a thinned
and flipped image of itself on the right side of the laser.  Have you seen
anything like this?

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