Equivalent area light and ambient source (Message 1 to 4 of 4)
From: Kari Kivisalo
Subject: Equivalent area light and ambient source
Date: 13 Oct 2001 05:21:28
Message: <3BC80796.67EA2F36@engineer.com>
#version 3.5; // beta 6
To verify that my assumptions about povray light sources
are correct I tried to make ambient source with the same
lighting properties as a diffuse area light.
I think I got it but there is this mysterious constant 2*pi
which is required. I think the 2 comes from the fading equation
attenuation=2/( 1+(d/fade_distance)^fade_power ). The intensity
at the surface of the light is two times higher than at the fade
distance. But where does the pi come from? :)
http://www.pp.htv.fi/kkivisal/area.pov
_____________
Kari Kivisalo
From: Jaime Vives Piqueres
Subject: Re: Equivalent area light and ambient source
Date: 13 Oct 2001 06:34:12
Message: <3BC818AC.633BECD5@ignorancia.org>
> To verify that my assumptions about povray light sources> are correct I tried to make ambient source with the same> lighting properties as a diffuse area light.
Very interesting... but the area version looks better, soft and
without artifacts.
> I think I got it but there is this mysterious constant 2*pi> which is required. I think the 2 comes from the fading equation> attenuation=2/( 1+(d/fade_distance)^fade_power ). The intensity> at the surface of the light is two times higher than at the fade> distance. But where does the pi come from? :)
Because light propagation is spherical? I've been reading a lot about
lighting lately, because I'm trying to relate common bulb properties to
pov light sources, and found many equations involving pi.
--
Jaime Vives Piqueres
La Persistencia de la Ignorancia
http://www.ignorancia.org/
From: Kari Kivisalo
Subject: Re: Equivalent area light and ambient source
Date: 13 Oct 2001 12:15:48
Message: <3BC868B4.30805D99@engineer.com>
Jaime Vives Piqueres wrote:
>> Very interesting... but the area version looks better, soft and> without artifacts.
It's faster too. This was fundamental research to advance
povray science :)
_____________
Kari Kivisalo
From: Wolfox
Subject: Re: Equivalent area light and ambient source
Date: 13 Oct 2001 18:14:52
Message: <3bc8bcdc@news.povray.org>
IIRC, isotropic propagation of electromagnetical waves (and therefore light)
causes energy to be distributed on a sphere surface with center on the point
emitter. So that pi constant may come out of that.
> Because light propagation is spherical? I've been reading a lot about> lighting lately, because I'm trying to relate common bulb properties to> pov light sources, and found many equations involving pi.
