Path: utzoo!attcan!uunet!cs.utexas.edu!usc!ucsd!helios.ee.lbl.gov!nosc!crash!jcs
From: jcs@crash.cts.com (John Schultz)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Blit Wanted
Message-ID: <2988@crash.cts.com>
Date: 4 Jun 90 00:07:36 GMT
References: <1032@mpirbn.UUCP> <2984@crash.cts.com> <1990Jun3.164446.12193@ameristar>
Distribution: comp
Organization: Crash TimeSharing, El Cajon, CA
Lines: 35
X-Local-Date: 3 Jun 90 17:07:36 PDT

In article <1990Jun3.164446.12193@ameristar> rick@ameristar (Rick Spanbauer) writes:
>In article <2984@crash.cts.com> jcs@crash.cts.com (John Schultz) writes:
>>faster than the blitter.  Until we see a 34020 or equivalent for the Amiga,
>>we can dust the blitter with the 32 bit processor for polygon fills.
>
>	The 34020 or even the 860 alone is not enough to do
>	realtime 3D graphics without additional support hardware.  The 860	
>	bus for example only does about 160 mByte/sec - consider that
>	to update a 1024x768x24 bit screen at even 30 hz takes about
>	71 mBytes/sec.  That is 71 mByte/sec just into the frame buffer,
>	neglecting completely instruction path traffic, processing time, 
>	etc.  I've been told that the 34020 can fill at only about
>	250 mBit/sec, so the time required to fill a 1024x768x24 display
>	is 1024*768*24/250x10^6 = ~75 mS (or about 13 fps max), again
>	neglecting insn fetch, processing time, etc.  
>	
 
  Yeah, yeah, and a Silicon Graphics 4D/GT 280 PowerVision isn't fast
enough for some applications either :-).  But, for certain applications,
we don't need 24 bit planes, or even 1024x768 resolution. Say for a
flight simulator we cut it down to 8 bitplanes, that's three times faster
or approximately 39 frames/sec.  A colleague at NASA Langley is running
20 frames/sec in Stereo 3D using 4D/GTs (Not the new PowerVision). But
I'm sure they could increase the rez or increase the detail to make the
frame rate "too slow".  Basicaly, given your hardware/software constraints,
do what you need in order to achieve the desired frame rate. I get
30 frames/sec in stereo 3D on an 030 Amiga, but I don't render a great
deal of large polygons.
  If a 34020 board is created for the Amiga, I hope they don't make the
same mistake as some PC vendors did by not supporting the lower resolutions
of the 34020.  Some applications require speed above all else, especially
real time simulations.


  John