This is a continuation of a post I made yesterday.  I have a lense (now not
hollow, thanks to the help I got here!), and it refracts light headed
towards the camera fine.  For example, a scene is distorted when the camera
looks through it.  But what I really want the lense for is to split up a
beam of light.  I am trying to use a spotlight or cylindrical light, but
when they pass through the lense they are unaffected.  I have tried the
caustics keyword, but it does not seem to do anything.  I am wondering if
only area or point lights are affected by lenses because of some wierd way
that the spot and cylinder lights work.  Is this true?  The reason I ask is
that I need to simulate a fanned laser for a presentation I am doing on
structured light vision.  Thank you so much... again.

Post a reply to this message

Lark wrote:
> ... But what I really want the lense for is to split up a
> beam of light. ...

People are working on this.  

There's a macro by Margus Ramst in  povray.text.scene-files, with an
example in povray.binaries.images. 

Peter Popov made an image title "The Spectral Orb", which also uses
color dispersion, in povray.binaries.images.  Scene source code is
available - at first I thought he used fake caustics, but no, it's done
with a bunch of light sources.  (Maybe this image should be the official
logo for the next POV-Ray?)

Nathan Kopp is patching POV-Ray itself to add caustics using an
algorithm called photon mapping, and has impressive results, though he
refers to his work as "vaporware, but this is a pretty thick vapor",
because it's not finished, has bugs.  Watch for his name in the
newsgroups.  See his images in povray.binaries.images.     When he
releases this, it ought to be faster and better than any macros (we all
hope).



-- 
Daren Scot Wilson
dar### [at] pipelinecom 
www.newcolor.com
----
"A ship in a harbor is safe, but that is not what ships are built for"
                                            -- William Shedd

Post a reply to this message

Daren Scot Wilson wrote in message <36B2FDD5.C451AD58@pipeline.com>...
>Lark wrote:
>> ... But what I really want the lense for is to split up a
>> beam of light. ...
>
>People are working on this.
>
>There's a macro by Margus Ramst in  povray.text.scene-files, with an
>example in povray.binaries.images.
>


My macro only does reflected caustics and requires the Superpatch;  it also
treats all light sources as point lights, so I doubt it'll help you. Sorry.
There are very few renderers around that do the thing you want and POV
currently isn't one of them. You might try out BMRT (Blue Moon Rendering
Tools); it can handle caustics to some extent and is freely downloadable.
But unless you are somewhat familiar with the RIB format and shaders, (and
have a Cray or sth., because caustics are slooooow), I suspect this is of no
use, either.
Wish I could help more.
Margus

Post a reply to this message

BMRT handles reflective caustics reasonably well.  It doesn't do
refractive caustics at all.

-Mike

Margus Ramst wrote:
> 
> Daren Scot Wilson wrote in message <36B2FDD5.C451AD58@pipeline.com>...
> >Lark wrote:
> >> ... But what I really want the lense for is to split up a
> >> beam of light. ...
> >
> >People are working on this.
> >
> >There's a macro by Margus Ramst in  povray.text.scene-files, with an
> >example in povray.binaries.images.
> >
> 
> My macro only does reflected caustics and requires the Superpatch;  it also
> treats all light sources as point lights, so I doubt it'll help you. Sorry.
> There are very few renderers around that do the thing you want and POV
> currently isn't one of them. You might try out BMRT (Blue Moon Rendering
> Tools); it can handle caustics to some extent and is freely downloadable.
> But unless you are somewhat familiar with the RIB format and shaders, (and
> have a Cray or sth., because caustics are slooooow), I suspect this is of no
> use, either.
> Wish I could help more.
> Margus

Post a reply to this message

Have you tested this? I once mailed Larry Gritz (the author) about this and
he said that refracted caustics are possible (but very expensive and do not
always give good results).
Quite frankly, I haven't tested it myself, since until very recently I had a
486 and caustics took forever.

Margus

Mike wrote in message <36B3A73E.52976134@aol.com>...
>BMRT handles reflective caustics reasonably well.  It doesn't do
>refractive caustics at all.
>
>-Mike
>

Post a reply to this message

If you want to email me a scene, I can render it for you (this will also
help me with my testing).  You'll have to explain what you want the result
to look like, though.

-Nathan

Post a reply to this message

I've tested the reflective caustics using bouncers...dog slow but it
works.  I couldn't imagine how to test refractive caustics since the
docs include nothing about it, plus I caught a thread on making faked
caustics using shaders on c.g.r.r (the other one), and Larry had said it
can't be done in BMRT without him changing some things and it wouldn't
be worth the trouble.

-Mike

Margus Ramst wrote:
> 
> Have you tested this? I once mailed Larry Gritz (the author) about this and
> he said that refracted caustics are possible (but very expensive and do not
> always give good results).
> Quite frankly, I haven't tested it myself, since until very recently I had a
> 486 and caustics took forever.
> 
> Margus
> 
> Mike wrote in message <36B3A73E.52976134@aol.com>...
> >BMRT handles reflective caustics reasonably well.  It doesn't do
> >refractive caustics at all.
> >
> >-Mike
> >

Post a reply to this message

Hello Lark!
I think that POV-Ray cannot do what you want just because only light ray
originating from the camera are refracted by objects having some refraction
value in the inside{} satement. You want to refract light rays originating from
the light source! To my humble knowledge light rays from light sources can only
be attenuated by objects between the source and the tested surface. This is
because the ray is traced back to the source and not from the source to the
lighted surface...
Greetings
   Karl-Heinz


Lark schrieb:

> ...looks through it.  But what I really want the lense for is to split up a
> beam of light.  I am trying to use a spotlight or cylindrical light, but
> when they pass through the lense they are unaffected.  I have tried the...
>

Post a reply to this message