Path: utzoo!attcan!uunet!etnibsd!denbeste
From: denbeste@etnibsd.UUCP (Steven Den Beste)
Newsgroups: comp.sys.amiga
Subject: Imagine 1.0 bugs and comments
Message-ID: <1190@etnibsd.UUCP>
Date: 10 Dec 90 19:10:02 GMT
Reply-To: denbeste@etnibsd.UUCP (Steven Den Beste)
Organization: Eaton Ion Beam Systems Division, Beverly, MA
Lines: 60

First off, I don't know anything about v0.9 - I ordered after 1.0 was released
and that's what they shipped me.

Comparisons to "Silver": As best I can determine, Imagine replaces Silver,
it doesn't augment it. There doesn't appear to be anything Silver does that
Imagine doesn't do better, faster and much, much easier!

With that out of the way: The "detail editor" is very nice, a pleasure to use.
Just for the hell of it, I tried duplicating an object which I created with
Silver: A miniature "Acropolis" made out of Au. With Silver, this object
took me the better part of two evenings. With Imagine, I had it in less than
an hour - and that included doing part of it twice because I did something
stupid and blew away part of it.

However, there are problems. Here are two:

The math to handle an object which is simultaneously reflective and
transparent (that is, filter>0) averages the light intensity derived from
each to determine the actual light intensity of a given pixel. This isn't
right - they should add. This leads to the odd result that if you've got
a clear sphere of glass on a surface with a dark sky, then though it should
be 100% transparent it nonetheless gets darker as the reflectivity is raised.
It begins to look like it is made out of smoked glass. (My first reaction
once I figured out what was going on was "They've perfected the Dark Emitting
Diode!". Just how do they figure that adding darkness and light results in
less light?)

The other problem I'm not yet clear on. With the 1000-to-2000 upgrade last year
I managed to make a deal with my dealer to retain my 1000 minus its keyboard.
Since then I found someone with a 1000 which was collecting dust, so I bought
it from him for small $, and am now using its keyboard. The upshot is that in
addition to my 2000 with 9 megabytes of RAM, I've got my old 1000 with 2.5M
and its 68020/68881 board. So I've been running the floating point version of
Imagine on it, mostly to compare calculation times. With a 16MHZ 68881, the
floating point version appears to be about twice as fast as the integer version
running on a stock 68000. To get this comparison, I had to duplicate a scene
setup. [Here's a trick to help this: Imagine stores file paths in its setup
files; if you use an "assign" device path, it will use that. You can then
copy a directory structure to another machine and make the same assign,
and it will work just dandy.]

Anyway, the image I transferred was of two wineglasses (one "spun", one
"swept" - I can't figure out what the difference is, and the documentation
doesn't say) on a "check" ground. For no reason which is at all apparent,
the floating point version mangles the direct view of the ground very badly.
Strangely, everywhere you see the ground THROUGH THE WINEGLASSES looks just
fine. Very strange.

I'm putting together a disk with these two problems and example traces to
demonstrate them and will be mailing them in. However, I'm completely
satisfied. My first really big project is going to be a car's-eye-view
of a roller coaster - should be pretty good once I figure out how to
make the camera follow complex paths, which doesn't look too hard to do.


Folks, this is one hell of a package. It is now tops on my list of "things to
show someone who says 'So what's so great about an Amiga?'".

Oh, and for those of you who've been struggling with Silver's documentation (or
lack thereof), the Imagine documentation is a hell of a lot better.