Path: utzoo!utgpu!watmath!watserv1!watdragon!bmacintyre
From: bmacintyre@watdragon.waterloo.edu (Blair MacIntyre)
Newsgroups: comp.sys.amiga.tech
Subject: Re: 3D-graphics
Message-ID: <18765@watdragon.waterloo.edu>
Date: 28 Nov 89 23:28:39 GMT
References: <1470@cc.helsinki.fi> <18344@watdragon.waterloo.edu> <3440@convex.UUCP>
Reply-To: bmacintyre@watdragon.waterloo.edu (Blair MacIntyre)
Organization: University of Waterloo
Lines: 56

swarren@convex.COM (Steve Warren) writes:
>bmacintyre@watdragon.waterloo.edu (Blair MacIntyre) writes:
>>PKONTKANEN@cc.helsinki.fi writes:
>>>	I haven't yet decided what kind of graphics routine to use.
>>>It should make possible to move anywhere in arbitrary 3D-world in
>>>real time. Does anybody have good ideas how to do this?
>>
>>On an Amiga, I feel quite confident in saying this is _not_ possible in
>>general  (see above ).
>
>What did the Rainbird guys do to get the 3D graphics for Starglider II?

Note that I said "In general"

I went on to say that as soon as you start making simplifying assumptions,
such as a fixed size world, things can be spead up.

Specifically, if you know the range of values you will be given, it 
should be possible to write a fixed point math library which is 
significantly faster than a generic floating point library.

An example of generality:

	I wrote a simple surface patch routine.
	If I use Bezier or Cardinal Spline basis matrices, the patch's
	 get rendered fine.
	If I use a normal B-Spline, it screws up.

	Why?

	The FFP library isn't precise enough.  Somewhere in there, 
	 I lost enough precision to screw it up.

	How do I know this?

	I recompiled with the IEEE library and it works just fine.

So, a simple assumption which would double the speed right now would
be that I wouldn't do things that would kill me with regard to FFP 
precision.  In a game _I'm_ writing, that's simple to enforce.

>I realise the landscape was pretty sparce compared to a city, but maybe
>a trade-off using similar techniques would work?

Like I said, restrict yourself, perhaps in area or viewing positions.
( although I don't think the last one will matter )

>Starglider is really smooth.  Maybe if the frame-rate was reduced by a
>factor of four a proportionate increase in complexity would be possible.
It is indeed.  I was impressed when I first saw it.


-- 
-- Blair MacIntyre, Professional Leech on Society ( aka CS Graduate Student )
-- bmacintyre@{watcgl, watdragon, violet}.{waterloo.edu, UWaterloo.ca}
-- Dating, verb: prearranged socializing with intent.