This is my feeble attempt at recreating Henric Wann Jensen's cool "classic
cardioid" caustic pattern (http://www.gk.dtu.du/home/hwj/ and
http://www.gk.dtu.dk/home/hwj/pictures/metalring.jpg) using Nathan Kopp's
Photon Patch for POV-Ray (http://www.nathan.kopp/photons.htm).

The problem with this (did I say feeble) attempt, is that as you can see,
the ray's are almost focused, but not quite. This is simply because the
light source is a skosh too high (as you can also see when you compare the
length of the shadow behind the object with the shadow in HWJ's version.
But... if I try to bring the light up any higher, all of the caustics
disappear.

I've posted the scene file in povray.text.scene-files if anyone would be so
kind to have a look.

By the way, I can see why HWJ used a wood-grain table setting. It really
does bring out the caustic effect. I just grabbed one of the standard wood
textures from the POV includes, but it gives the desired effect.

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Attachments:
Download 'DavesRing.JPG' (26 KB)

Preview of image 'DavesRing.JPG'

The problem will probably be corrected if you increase the 'autostop' angle.
Set it to 45 (degrees) and things should work.  Soon I'll have a FAQ that
explains this.

-Nathan

David Cook wrote:
> 
> This is my feeble attempt at recreating Henric Wann Jensen's cool "classic
> cardioid" caustic pattern (http://www.gk.dtu.du/home/hwj/ and
> http://www.gk.dtu.dk/home/hwj/pictures/metalring.jpg) using Nathan Kopp's
> Photon Patch for POV-Ray (http://www.nathan.kopp/photons.htm).
> 
> The problem with this (did I say feeble) attempt, is that as you can see,
> the ray's are almost focused, but not quite. This is simply because the
> light source is a skosh too high (as you can also see when you compare the
> length of the shadow behind the object with the shadow in HWJ's version.
> But... if I try to bring the light up any higher, all of the caustics
> disappear.
> 
> I've posted the scene file in povray.text.scene-files if anyone would be so
> kind to have a look.
> 
> By the way, I can see why HWJ used a wood-grain table setting. It really
> does bring out the caustic effect. I just grabbed one of the standard wood
> textures from the POV includes, but it gives the desired effect.
> 
>  [Image]

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Thanks Nathan (and let me join the line of appreciative users of your
patch)! Here's the resulting image, and I've posted the source as a followup
in povray.text.scene-files. I have to humbly admit that I'm a little unclear
on what's going on with the photon parameters. I'll be looking forward to
your FAQ.

Nathan Kopp <Nat### [at] Koppcom> wrote in message
news:36F7B744.D92F3465@Kopp.com...
> The problem will probably be corrected if you increase the 'autostop'
angle.
> Set it to 45 (degrees) and things should work.  Soon I'll have a FAQ that
> explains this.
>
> -Nathan
>
> David Cook wrote:
> >
> > This is my feeble attempt at recreating Henric Wann Jensen's cool
"classic
> > cardioid" caustic pattern (http://www.gk.dtu.du/home/hwj/ and
> > http://www.gk.dtu.dk/home/hwj/pictures/metalring.jpg) using Nathan
Kopp's
> > Photon Patch for POV-Ray (http://www.nathan.kopp/photons.htm).
> >
> > The problem with this (did I say feeble) attempt, is that as you can
see,
> > the ray's are almost focused, but not quite. This is simply because the
> > light source is a skosh too high (as you can also see when you compare
the
> > length of the shadow behind the object with the shadow in HWJ's version.
> > But... if I try to bring the light up any higher, all of the caustics
> > disappear.
> >
> > I've posted the scene file in povray.text.scene-files if anyone would be
so
> > kind to have a look.
> >
> > By the way, I can see why HWJ used a wood-grain table setting. It really
> > does bring out the caustic effect. I just grabbed one of the standard
wood
> > textures from the POV includes, but it gives the desired effect.
> >
> >  [Image]

Post a reply to this message

Attachments:
Download 'DavesRing2.JPG' (31 KB)

Preview of image 'DavesRing2.JPG'