POV-Ray : Newsgroups : povray.binaries.images : HDRI, why? Server Time
14 Aug 2024 05:17:09 EDT (-0400)
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From: Jaime Vives Piqueres
Subject: Re: HDRI, why?
Date: 4 Jan 2003 05:59:01
Message: <20030104115900.32235936.jaimevives@ignorancia.org>
On Sat, 04 Jan 2003 08:55:34 +1100
Daniel Matthews <dan#@3-e.net> wrote:

> That is very nice work, but where are the photons?
> Could you work a crystal ball into your test scene and show refraction
> and reflection working with the fake HDRI environment?
 
  I've not tried it yet, but I think it should work as with any other
scene with ambient light only. That is, only for very HQ rad settings.

-- 
Jaime Vives Piqueres
		
La Persistencia de la Ignorancia
http://www.ignorancia.org


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From: Christopher James Huff
Subject: Re: HDRI, why?
Date: 5 Jan 2003 20:33:47
Message: <cjameshuff-DA9B20.20234505012003@netplex.aussie.org>
In article <3e1560f2@news.povray.org>, "Hugo Asm" <hua### [at] post3teledk> 
wrote:

> But with reflections, the docs says "POV-Ray uses a limited light model that
> cannot distinguish between objects which are simply brightly colored and
> objects which are extremely bright" therefore we have the
> reflection_exponent keyword... So that shouldn't work in favor of HDR, but
> I'm not fully certain about it.

The documentation is a bit inaccurate there (just wrong actually, colors 
are only clipped at the last stage, after being calculated), reflection 
handles values > 1 just fine, and nothing stops you from specifying 
realistic values. The problem is that values elsewhere are usually 
specified in the range [0, 1]. The reflection_exponent feature is a 
simple hack that modifies the calculations unrealistically to compensate 
for inaccurate settings.

There is nothing HDRI does that existing features couldn't do with 
greater physical accuracy, it just does it with less render time and 
scene/lighting setup. Instead of building and rendering a detailed and 
painstakingly adjusted scene, you use an existing high dynamic range 
image which has samples of the data you would have to compute, and 
interpolate that data.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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