POV-Ray : Newsgroups : povray.general : Obtaining Photon Co-Ordinates for Photon Density Estimation? Server Time: 22 Oct 2017 21:00:53 GMT
  Obtaining Photon Co-Ordinates for Photon Density Estimation? (Message 1 to 2 of 2)  
From: Fudz4
Subject: Obtaining Photon Co-Ordinates for Photon Density Estimation?
Date: 3 May 2017 19:50:00
Message: <web.590a33e8f7d2ce904af85fbb0@news.povray.org>
Hey guys, you may have seen my post a while ago, I was reading this paper and
wondering how exactly he query's the scene to collect photon data?

Does anyone know how I can go about experimenting with photon desnity estimation
like he does? Or how to segment the scene in k-d trees?

Thanks.

http://cs.swan.ac.uk/~csbenjamin/research/hpm.pdf


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From: Kenneth
Subject: Re: Obtaining Photon Co-Ordinates for Photon Density Estimation?
Date: 4 May 2017 11:20:00
Message: <web.590b0d7890133ccf883fb31c0@news.povray.org>
Most of that research paper is above my understanding. However, I think I can
make a *few* safe comments, regarding POV-Ray.

The paper speaks of 'photon mapping' as an all-inclusive rendering technique
there. POV-ray also has 'photon mapping'--but the *meaning* is somewhat
different. POV-ray's use of 'photons' is solely to produce caustics (from light
shining through transparent glass, etc), while 'global illumination' is done
with the 'radiosity' feature. (Both photon-maps and radiosity 'maps' *can* be
pre-generated and saved, then used for the final render, if desired.) But
POV-ray doesn't use so-called photon-mapping for its *entire* rendering
pipeline. I think the paper is describing a different approach.

The overall technique described on the FIRST page of the paper has great
similarity to POV-ray's radiosity feature-- you could almost replace 'photon
mapping' there with 'radiosity', and it would make sense.

In the past, I *have* seen newsgroup posts here about various 'forks' or
unofficial versions of POV-Ray that might use some kind of photon-mapping or
'Monte Carlo' approach to overall rendering; you could try doing a search.

Over the years, it has been said many times in the newsgroups that POV-ray's
overall raytracing technique cannot make use of a GPU's power, just the CPU (or
multiple CPUs, as it does work with parallel processing.) I don't know the
technical reasons for non-GPU use, but I think raytracing itself is difficult to
implement. Of course, that may have changed; I've seen other research papers
that talk about 'real-time raytracing.' It has even been discussed here in the
newsgroups, from time to time.

Sorry to say that I don't know much at all about k-d trees, so I can't help
there.


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