Conference hydra::amiga_v1

483.0. "Amgia World Ray-tracing article..." by LEELA::MYEE (Crunchy frog) Wed Apr 29 1987 14:42

    	Found this on the USENET and it generated alot of replies so I'm
    posting it here.  I personally do not have a Amiga yet (waiting
    for the 2000 and 500, if they ever come out).  May be I should get
    a Amiga 1000 (Zorro bus is different though).  What you think ??
    
    
Newsgroups: comp.sys.amiga,comp.graphics
Path: decwrl!decvax!ucbvax!ucbcad!ames!rutgers!uwvax!puff!upl
Subject: Amgia World Ray-tracing article...
Posted: 10 Apr 87 15:43:17 GMT
Organization: U of Wisconsin CS Dept
Xref: decwrl comp.sys.amiga:3504 comp.graphics:475
 
Has anyone else bothered to read the article in the latest Amiga World
written by the guy who did juggler? The man clearly has a decent knowledge
of ray tracing on at least a basic level, but makes some serious boo boos in
other parts of the article.
 
FLAME ON.......
 
 The big one is he defines B-rep (boundry represntation) as a RENDERING
 technique!!! He compares it to ray-tracing, which of course is like
 comparing a steak to a1 steak sauce!! (For those not into graphics,
 B-rep is an object space representation technique- in other words a
 way of mathematically defining a 3d object by specifying its edges.
 One can certainly ray trace a B-rep object - in fact I am working on
 a system that among other things will do just that!!)
 
 The other statement I found particularly objectionable was his statement that
 "we now have the ray tracing time down to an hour. Considering professional
 systems running on Crays...take 2or 3 minutes, our Amiga isn't doing
 badly". Maybe not, but he forgets to mention that when doing animation, which
 was a major thrust of his article, the time for a single frame gets multiplied
 many times over, and thus time delays do as well. Using my pocket calculator,
 and figuring the 24fps of standard film, I get a 14400 hours of
 continous calculation for a ten minute film, or about 2 YEARS of continous
 calculation!!!!
 
 Other than this, his article was really quite nice, a good low level
 introduction to some of the simpler concerns in digital scene simulation
 using ray tracing- I just wish he had stuck to the areas he knows about,
 and not felt the need to gloss over its short comings.
 
 FLAME OFF
 
 Jeff Kesselman
 uhura!captain
 (captain @ The UW-Madison Undergraduate Project Lab)

    I believe that the expansion buss on the 500 is electrically identicle
    to the 1000 buss, but exits on the left hand side of the machine.
    
    Manufacturers of expansion devices will merely have to repackage
    their boards, not funtionally re-design them.
    
    I don't think the 2000 has ANY 86 pin conectors, but instead uses
    the new 100 pin Zorro-spec boards entirely.  If I am incorrect on
    either of these points, I'm sure someone will correct me.

    Re: .1  
    You are right ! I mean you are wrong and someone is immediately
    going to correct you :-).
    A2000 has 5 zorro Buffered Bus extensions and ONE 86 pins UNBUFFERED.
    
    There have been rumors in the past that some software was not running
    on the Amy2.  Wrong ! We have extensilvely tested ALL software here
    available ( >> 250 disks ) and have not found a single program not
    working.
   

    re: original note
    
    I found the Amiga World issue and typed the whole thing. Unfortunately
    I can't manage to get it to work.
    
    Has anyone some working "test data" I can use to understand where
    the problem is ? I'm interested in Ascii stuff cause my computer
    is a Mac (forgive me... 8-) )
    
    Help me !!!!
    
    Angelo

>    I found the Amiga World issue and typed the whole thing. Unfortunately
>    I can't manage to get it to work.
    
	Neither could I. The code does have some serious flaws in it. The
     best I could get was a couple of spheres on a checkerboard, with
     no reflections. Didn't bother to go any further with it, as it wasn't
     that interesting.

>    Has anyone some working "test data" I can use to understand where
>    the problem is ? I'm interested in Ascii stuff cause my computer
>    is a Mac (forgive me... 8-) )
    
	For some real ray-tracing code, look in:

	pasta::tater$:[scott.public.ray.mtv]

	Hope your MAC has color!