Path: chuka.playstation.co.uk!news
From: sceetech <ps_yaroze@interactive.sony.com>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: 3D engines
Date: Wed, 09 Apr 1997 15:10:17 +0100
Organization: SCEE
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Message-ID: <334BA349.28A9@interactive.sony.com>
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Jim wrote:
> 
> Alex Amsel wrote:
> 
> >
> > This 'god knows what' section is also important - I don't know what gs
> > does underneath. It doesn't matter how optimized it is, there are
> > almost always better ways of providing the data. Without knowing
> > internals it is hard to improve on this part.
> >
> 
> This is something I also find important.  You can always write better
> code if you know what the 3rd party calls are doing.  My case in point
> is that I always assumed that memcpy under djgpp moved memory around
> most efficiently.  It wasn't until I looked at the assembler for it I
> discovered that it did a rep movsb, regardless how the memory was
> aligned and how long it was.  This was such an easy optimization that
> essentially quadrupled performance.
> 
> For example how do I know that RotMatrixX,Y and Z are just as fast as
> RotMatrix?
> 
> Another point, I would like to draw 3d lines.  But from initial browsing
> through the manuals it looks like I cant draw a line from x1,y1,z1 to
> x2,y2,z2.  Now it looks like I will have to do the perspective
> transformation myself into a 2d line and plot that?
> 
> Another omission is pixel plotting.  The answer I received last week for
> this is just draw a line with the same start/end points, and That pixel
> plotting was not really a requirement for a 3d engine.  It is for my 3d
> engine that produces particle effects for explosions & smoke.
> 
> Now the overhead for transforming a pixel would be outrageous using
> gslib.  It would be so much efficient to do the whole thing in asm get
> the gpu to draw them directly.  I may be able to do this via the
> loadimage directly into the double buffer region.  I'll suck it and see.
> 
> Sorry for the ramblings.
> 
> Regards
> 
> Jim

There is no 3d line drawing, simple because a line has no width, so its
impossible to plot. You could do a poly4 and have a line with width. 

I find with all this gte gpu stuff that it makes very little difference,
your still stuck to 50 or 25 frames per second (60/30 NTSC).

Stuart