Alright, everyone keeps asking about caustics, of one sort or another,
so maybe next week I'll tinker around with adding it.  

Before I start, though, has anyone made or found a list of previous
attempts that have failed?  I'd hate to reinvent a wheel and discover
the hard way that it won't roll...


-- 
Daren Scot Wilson
Member, ACM
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

Interesting that you should mention this.  I recently got the O.K. from one of
my professors to do an undergraduate research project next semester to add
backwards raytracing to POV-Ray.  I've been doing a lot of thinking about this
over the past month and I've got some ideas on how to do it which turned out to
be very similar to the "photon map" by Henrik Wann Jensen.  Jensen's work with
photon maps seems to have been a success, both in terms of image quality and in
rendering speed.  You can read about it at:
http://www.gk.dtu.dk/home/hwj/
http://www.gk.dtu.dk/home/hwj/papers/ewr7/index.html

An example of rendering time (from Jensen's paper):
  Machine: 100Mhz Pentium with 32 megs of RAM
  -A diffuse Cornell box (standard radiosity test scene)
    Preprocessing (about 300k 'photons'): 67 sec
    Rendering (at 1280x960): 8 min
  -A glossy Cornell box
    Preprocessing (about 380k 'photons'): 56 sec
    Rendering (at 2560x1920): 50 min

A render of the diffuse Cornell box at the same resolution by the Radiance
renderer took 60 minutes.

My original work will not be as extensive as Jensen's, but I will try to do it
in such a way that future enhancements will be easy for myself or others to
add.

Because I'll be doing this for college credit, I will be able to justify
spending some extra time on POV. :-)  However, input from other POV programmers
will be very helpful.  If I can get enough done, I really want to combine this
with your dispersion patch, which could produce some really nice images.

-Nathan Kopp

Daren Scot Wilson wrote:
> 
> Alright, everyone keeps asking about caustics, of one sort or another,
> so maybe next week I'll tinker around with adding it.
> 
> Before I start, though, has anyone made or found a list of previous
> attempts that have failed?  I'd hate to reinvent a wheel and discover
> the hard way that it won't roll...
> 
> --
> Daren Scot Wilson
> Member, ACM
> 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

BTW... I must say 'thanks' to Ron Parker for giving me those photon-map URLs.
They have been most interesting and extremely useful.

-Nathan

Post a reply to this message

This sounds like a really exciting project!  I hope you succeed.

One request.  When you are done, those of us who don't have the necessary
compilers to compile POV-Ray (and can't afford the hundreds of $$$ to get
one to do just this compile), would really appreciate your making a copy of
the executable (in my case for Win98/NT4.0) available with the patch.  This
is not the case with Daren's dispersion patch (and I don't know how many
others) and the lack of an executable has kept me for using that capability.

Thanks and good luck!

Jim


Nathan Kopp wrote in message <3669F93E.B9FDC9BA@Kopp.com>...
>Interesting that you should mention this.  I recently got the O.K. from one
of
>my professors to do an undergraduate research project next semester to add
>backwards raytracing to POV-Ray.  I've been doing a lot of thinking about
this
>over the past month and I've got some ideas on how to do it which turned
out to
>be very similar to the "photon map" by Henrik Wann Jensen.  Jensen's work
with
>photon maps seems to have been a success, both in terms of image quality
and in
>rendering speed.  You can read about it at:
>http://www.gk.dtu.dk/home/hwj/
>http://www.gk.dtu.dk/home/hwj/papers/ewr7/index.html
>
>An example of rendering time (from Jensen's paper):
>  Machine: 100Mhz Pentium with 32 megs of RAM
>  -A diffuse Cornell box (standard radiosity test scene)
>    Preprocessing (about 300k 'photons'): 67 sec
>    Rendering (at 1280x960): 8 min
>  -A glossy Cornell box
>    Preprocessing (about 380k 'photons'): 56 sec
>    Rendering (at 2560x1920): 50 min
>
>A render of the diffuse Cornell box at the same resolution by the Radiance
>renderer took 60 minutes.
>
>My original work will not be as extensive as Jensen's, but I will try to do
it
>in such a way that future enhancements will be easy for myself or others to
>add.
>
>Because I'll be doing this for college credit, I will be able to justify
>spending some extra time on POV. :-)  However, input from other POV
programmers
>will be very helpful.  If I can get enough done, I really want to combine
this
>with your dispersion patch, which could produce some really nice images.
>
>-Nathan Kopp
>
>Daren Scot Wilson wrote:
>>
>> Alright, everyone keeps asking about caustics, of one sort or another,
>> so maybe next week I'll tinker around with adding it.
>>
>> Before I start, though, has anyone made or found a list of previous
>> attempts that have failed?  I'd hate to reinvent a wheel and discover
>> the hard way that it won't roll...
>>
>> --
>> Daren Scot Wilson
>> Member, ACM
>> 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

Jim Kress wrote:

> This sounds like a really exciting project!  I hope you succeed.
>
> One request.  When you are done, those of us who don't have the necessary
> compilers to compile POV-Ray (and can't afford the hundreds of $$$ to get
> one to do just this compile), would really appreciate your making a copy of
> the executable (in my case for Win98/NT4.0) available with the patch.  This
> is not the case with Daren's dispersion patch (and I don't know how many
> others) and the lack of an executable has kept me for using that capability.
>
> Thanks and good luck!
>
> Jim

Perhaps our good friend Mr. Parker will consider adding
the dispersion patch to the super patch. (hint ! hint !).

Ken Tyler

Post a reply to this message

On Sun, 06 Dec 1998 07:49:00 -0800, Ken <tyl### [at] pacbellnet> wrote:

>Perhaps our good friend Mr. Parker will consider adding
>the dispersion patch to the super patch. (hint ! hint !).

Perhaps.  I haven't looked at it yet to see how difficult it
will be.  The previous dispersion patch was a major code change.

Post a reply to this message

Ron said:
> I haven't looked at it yet to see how difficult it
> will be.  The previous dispersion patch was a major code change.
> 

Well, this one's a nice, simple change.  Just replaces one function in
one source file with some fancier stuff, and small changes to a few
other files to add the new keywords.    Should blend in with superpatch
or other patches no trouble.


As for those who ask for an executable, I wish I could be helpful, but
my home computers are strictly Linux only.  I suppose I should at least
put the linux version of dispersion-povray on my web site.




-- 

Daren Scot Wilson
Member, ACM
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

A certain Mr. Kopp wrote:
> and I've got some ideas on how to do it which turned out to
> be very similar to the "photon map" by Henrik Wann Jensen.  Jensen's work with
> photon maps seems to have been a success, both in terms of image quality and in
> rendering speed.  You can read about it at:
> http://www.gk.dtu.dk/home/hwj/
> http://www.gk.dtu.dk/home/hwj/papers/ewr7/index.html

Yes, nice stuff!   I was surfing for caustics research yesterday, and
came upon another project, by Steve Collins, for his PhD thesis that
involved a complete ray tracing lighting model, including nice caustics,
at http://isg.cs.tcd.ie/scollins/work.html

There seem to be several independent attempts to add caustics and
related effects to ray tracers - we should gather a list of all them,
summarize each put that on a web page.

I wonder if the POV-Team had considered caustics in the past?  

-- 

Daren Scot Wilson
Member, ACM
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

On Mon, 07 Dec 1998 01:25:07 +0000, Daren Scot Wilson
<dar### [at] pipelinecom> wrote:

>Ron said:
>> I haven't looked at it yet to see how difficult it
>> will be.  The previous dispersion patch was a major code change.
>> 
>
>Well, this one's a nice, simple change.  Just replaces one function in
>one source file with some fancier stuff, and small changes to a few
>other files to add the new keywords.    Should blend in with superpatch
>or other patches no trouble.

I've looked at it and it looks like it should be no problem to add,
but I'll have to integrate it with wyzpov, which might be no small
feat.  BTW, your patch file seems to have some duplicated lines in
express.c and a couple other places, unless I'm just not reading
it right (which is quite possible)

Post a reply to this message

>  BTW, your patch file seems to have some duplicated lines in
> express.c and a couple other places, unless I'm just not reading
> it right (which is quite possible)

Just checked... ya, oops, those really are duplicated lines - just nuke
the extras.  I will make a new patch and post it here.  There's a small
improvement to be added, too.

-- 

Daren Scot Wilson
Member, ACM
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