POV-Ray : Newsgroups : povray.binaries.images : Lightdome testing : Re: Lightdome testing Server Time
1 Aug 2024 10:12:18 EDT (-0400)
  Re: Lightdome testing  
From: Trevor G Quayle
Date: 10 Sep 2008 10:25:00
Message: <web.48c7d7c66d308f3781c811d20@news.povray.org>
Looks like a good start.

I spent quite a while developing a lightdome system (
http://news.povray.org/povray.binaries.scene-files/message/%3Cweb.46488bca4e05d400c150d4c10%40news.povray.org%3E/#%3Cwe
b.46488bca4e05d400c150d4c10%40news.povray.org%3E)

I started with unifrom sampling and using only lights over a certain threshold.
I found that this was using a lot of lights, but it ends up dropping out lower
ambient lighting effects, and you also end up with a very high number of lights
to look effective.  I ended up using the median cut method with very good
success.  With median cut, rather than a uniform distribution of light sources
with varying intensity, you get light sources with uniform intensity (varying
colour though) at non-uniform spacing.  It is highly effective at capturing
both bright and low ambient light sources and gives much smoother results with
fewer lightsources.  I even took it one step further and introduced area
lights, which let me use even fewer effective light sources with smoother
results.
It works very well because it does account for all lighting in the scene, areas
with brighter lights just get more lightsources, while ambient areas get fewer.

The real limitation in using median-cut is what the sampling size used for the
original HDR.  The finer the image is broken down, the more accurate it gets
(i.e., doesn't miss very small point light sources), but it gets much more
computationally intense so you need to find the compromise size.

I've been away from the boards for a while with RL, so I missed a lot of your
earlier development.  I may check in occasionally as I get time if you need any
assitance with your work or how mine went together (At this point, I barely
remember how some of the features of mine work behind the scenes, as I worked
on the code for so long that I forgot...)

-tgq


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