Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!aplcen!haven!udel!princeton!phoenix!gauss!markv
From: markv@gauss.Princeton.EDU (Mark VandeWettering)
Newsgroups: comp.graphics
Subject: Re: Fractals, and Philosophy of Science
Message-ID: <12782@phoenix.Princeton.EDU>
Date: 8 Jan 90 15:40:57 GMT
References: <119.256E54C5@uscacm.UUCP> <1247@becker.UUCP> <9144@cbmvax.commodore.com> <6780@lindy.Stanford.EDU> <9215@cbmvax.commodore.com> <12707@phoenix.Princeton.EDU> <1990Jan7.143923.8647@hellgate.utah.edu>
Sender: news@phoenix.Princeton.EDU
Reply-To: markv@gauss.Princeton.EDU (Mark VandeWettering)
Organization: Princeton University
Lines: 71

In article <1990Jan7.143923.8647@hellgate.utah.edu> thomson@cs.utah.edu (Rich Thomson) writes:
>In article <12707@phoenix.Princeton.EDU> markv@gauss.Princeton.EDU
	[ I started more of this mess with opinions about the 
	  subjective nature of the "realism" of fractal imagery ]

>In an attempt to bring this back around to graphics, think back on the
>methods used to generate most computer imagery in use today.  Shading
>equations often contain lots of little parameters that are tweaked by the
>programmer -- often judged on "purely subjective criteria" in order to get
>the best looking image.

	Agreed, but this is changing.  Witness the work done with radiosity,
	which attempts to provide an accurate simulation of radiative 
	transfer in the visual spectrum.  There is a high element of 
	physics involved in what they do.  Many of Kajiya's papers in recent
	years attempt to deal with problems in lighting and lighting models.
	Things are improving.

>That's what I feel graphics is about -- getting the best image for what you
>want.  If the image you want comes more easily from a fractal model, who
>cares if it isn't a valid "natural model"?  Graphics programmers aren't
>geologists or biologists or botanists -- they aren't seeking a model for
>explanatory purposes.  
	
	Well, that might be what you feel graphics is all about, but I 
	wouldn't say your classification is universal for all graphics users.
	Some graphics programmers are botanists, and geologists, and
	biologists.  And physicists and artists and students and.....

>They are seeking a model for imaging purposes.  The
>two are very different.  Some of these techniques have managed to satisfy
>both needs (L-systems for example), but mostly graphics is just a "hack"
>that produces a "nice" image.  

	I think that much of graphics is a hack.  More of research is 
	aimed at improving the formality of computer graphics.

>If you want to completely and accurately
>model a mountain, you might as well sketch it by hand because the compute
>time necessary to model the complete developmental cycle of a terrain is
>prohibitive; 
	
	Well, sketching it by hand implies that you have the terrain in 
	front of you, which is certainly not a certain matter.  But if 
	you are saying that fractals are good at creating cheap effects
	at a high level of visual complexity, then I agree.  If you say
	that these are useful in computer graphics I agree that they are
	useful but not the end of the evolution of graphics modeling.  If 
	you try to claim that there is some subjective comparison between
	fractal models and the objects they mimic, then I might even yield.

	If however, you claim that fractal models have some analytical 
	relationships to the objects they model, I merely ask to be given
	proof.

>not to say that knowledge from the sciences is useless in
>helping you obtain a good image, but that the technique used to get a good
>image doesn't necessarily have to come from a "scientifically accurate"
>model.
	
	There are perhaps two aims to computer graphics:

		1. to "describe" a scene visually
		2. to "simulate" a scene visually
	
	Mr. Thomson appears to say that the aim of computer graphics is 1.
	I tend to believe that more of 1 is done, but the better aim is
	to shoot for 2.  Yes its complex and nasty, but hey, what else are
	us researchers supposed to be paid for :-)

Mark VandeWettering