Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!milton!wiml
From: wiml@milton.u.washington.edu (William Lewis)
Newsgroups: comp.graphics
Subject: Re: good radiosity question
Message-ID: <1991May26.020248.10869@milton.u.washington.edu>
Date: 26 May 91 02:02:48 GMT
References: <20917@ogicse.ogi.edu>
Organization: University of Washington, Seattle
Lines: 28

In article <20917@ogicse.ogi.edu> aburke@ogicse.cse.ogi.edu (Andrew Burke) writes:
>
>a few days ago wuly@vax5.cit.cornell.edu queried the net:
>>> Howdy.
>>> 	I have written a combination radiosity/raytracing rendering system
>>> (whew!) and I'm somewhat confused on one point: I have a scene of 5 walls,
>>> 10x10, with a light 3x3 pointing at one of the walls.  Now with 90% diffuse
>>> surfaces, the relative energy out of the wall *behind* the light (i.e. light
>>> left the lightsource, hit the wall in front, and was re-radiated to the back
>>> wall, and re-radiated again) is about 1/1000 the energy leaving the light.
>>> This seems wrong. ...
>
>I have basically the same problem.   ...

    I'm hardly an expert in computer graphics, but might the problem
be that the human eye has a pretty nonlinear response to intensity?
As I remember most human senses are logarithmic in nature, not linear
(presumably for greater dynamic range --- this is why you can't see
a flashlight beam in bright sunlight...)  So this factor of 1000 difference
in power would correspond to, say, a factor of 3 difference intensity,
which seems reasonable. Try taking the log of the intensity or something
before displaying.


-- 
 wiml@milton.acs.washington.edu       Seattle, Washington   
     (William Lewis)   |  47 41' 15" N   122 42' 58" W  
 "Just remember, wherever you go ... you're stuck there."