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From: jfoust@well.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: Interchange program for Sculpt 3D and Videoscape3D
Message-ID: <4490@well.UUCP>
Date: Thu, 19-Nov-87 21:45:59 EST
Article-I.D.: well.4490
Posted: Thu Nov 19 21:45:59 1987
Date-Received: Sun, 22-Nov-87 04:07:36 EST
References: <4443@well.UUCP>
Lines: 89
Summary: ore comments


> slightly nonplanar to some extent, simply because their coordinates are
> not specified with infinite precision.  If perfect planarity is
> desired, one can always construct objects out of only triangles.  
    
In some of the objects on the VideoScape disk, the non-coplanarity is as
much as 20 percent.  Hey, it works, even though it doesn't seem
academically elegant.


> Actually, in that case the blue window is drawn first and then a black
> outline polygon is drawn around the window ("outline only" is one of
> the rendering modes for a polygon).  Both of these are examples of

I misinterpreted the VideoScape file, this was my mistake.  In Sculpt,
edges and points are not rendered at all.  Only triangles are rendered. 
Sculpt edges and points have no color characteristics.  I do not translate
outline polygons to Sculpt form.


> A scene rendered by VideoScape will look nicer (and still be drawn much
> faster) than a scene rendered by Sculpt 3D's painting mode when there
> are lots of colors in the scene, because VideoScape can use dithering
> to create more subtle shading than exists in Sculpt's computed pallette
    
Do you mean to say "lots of colors" equals "eleven fixed colors, plus fixed
shades of those colors"?  My point was that Sculpt does choose a new
palette for the picture, which looks much nicer than a fixed palette.  

An example of the benefits of a flexible palette are obvious when you move
around a simple object, like a cube.  In VideoScape, the shades of the
rotating sides go "clunk, clunk, clunk" when making the transition from
light to dark, because of the limits of dithered coloring.  To be fair,
this is true of any any non-HAM rendering scheme, so this isn't a
particular criticism of VideoScape.

To me, the best situation would be both a fixed but user-settable palette
and dithering to get shades. (Changing palettes between frames leads to
complications in compressing the resulting animation files.)  Also, it
no one has explored the use of dither patterns with two colors, instead of
one color and black.  They used to squeeze dozens of extra colors from the
Apple ][ by placing different colored pixels next to each other.  In Amiga
interlace, it works quite well, according to some experiments I've done.


> beams or atmospheric shadows.  Colors can be mixed to get 121 different
> choices (not counting the different rendering modes), and the pallette
> can be set by the user to any of the Amiga's 4096 colors.

Ah, good.


> None of the Amiga 3D programs have done too well in this regard, and
> the problem is not a lack of objects, but a shortage of people who want
> to give out their creations.  However, there are lots of user-created
> objects out there (some of the ones I've seen are incredibly complex,
    
I am sure many people keep their objects to themselves, just like
programmers do with programs they create.  Programmers are enough like
artists that I would expect the proportions to be the same.  I've been
looking for objects like mad, and found very few.  I've found few
animations, too.  My point is, most users/buyers of VideoScape find graph
paper, EGG and OCT to be very difficult to use to create objects. 
Certainly this is the reason Aegis plans to market Modeler 3D:  VideoScape
users have complained.


> >           ...Allen Hastings stopped creating objects on graph paper
> >months ago when his friend Stuart Ferguson wrote this object editing
> >program.
> 
>     I'm afraid that is completely untrue.  I have found very efficient 

You had once told me you'd been using Stuart's program for some time prior
to his showing at BADGE and Aegis, and I incorrectly assumed it was
preferable to graph paper.


> This posting is a response to a message by John Foust in which he
> explains some of the difficulties he had writing a conversion program
> for VideoScape 3D and Sculpt 3D object description files.

> with his object translation program.  Sorry if you had trouble writing
> it, but nobody said it was going to be easy!

Bringing any commercial product to market is never easy, otherwise everyone
would do it, and do it well.  More precisely, I had trouble understanding
implementation and design choices in both VideoScape and Sculpt.  Nowhere 
did I complain about writing *my* program.  :-)