From: kurt@cashew.asd.sgi.com (Kurt Akeley)
Subject: Re: Reality Engine performance
Organization: Silicon Graphics, Inc.
Date: Thu, 23 Jul 1992 21:59:38 GMT

-- 
In article <1992Jul23.164303.13858@eagle.lerc.nasa.gov>, tohanson@gonzo.lerc.nasa.gov (Jeff Hanson) writes:
|> In general I agree with Martin.  Scientific visualization in general,
|> and CFD visualization in particular are polygon bound and not texture
|> bound.  We don't use the bitplanes we have now, so the extra ones
|> in the RealityEngines aren't going to do us any good.

RealityEngine does not store textures in the bitplanes, but rather
in separate texture memory.  The additional bitplanes may indeed be of
benefit to you.  See below.

|> Here is what I think a good ViSC machine would be -
|> 
|> 1. As high a polygon rate as possible.

The benchmark polygon rate of RealityEngine isn't much higher in some
cases than the VGX numbers, but the usable performance is higher.
Reasons include higher fillrate, more fifos between graphics engines,
much faster clipping, backface culling before lighting, much faster
implementation of complex lighting algorithms, etc.

|> 2. As much screen resolution as possible.  This is important for highly
|>    detailed grids and for seeing things that differ widely in size in
|>    physical space coordinates.

Two of the three bitplane configurations of RealityEngine support 1600x1200
out of the box (including the monitor).  This is accomplished by trading
bitplane depth (number of bitplanes) for bitplane area, which RealityEngine
is designed to do gracefully.

|> 3. Antialiasing for lines and polygons.  The VGX Accumulation Buffer is
|>    a good example of this since it is progressive.  That is, you get
|>    maximum responsiveness when interactive (moving) and you get a better
|>    picture when you stop.

Most of the additional bitplanes in RealityEngine are there to support
full performance rendering of antialiased points, lines, and especially
polygons.  Because they are there, you can generate antialiased
images without having to presort graphics primitives.  Like a zbuffer,
a cost of additional bitplane resources simplifies application programming
and increases performance.

|> 4. Double buffer for 24 bit (or higher) color with 12 bit colormaps available.

RealityEngine supports 12 bits per color component (48 bit RGBA) in single,
double, and quad buffer configurations.  Quad buffer supports stereo in
a window, with square pixels, and no incorrect interactions with the window
system (pulldowns, menus, etc. work correctly).

Several 12-bit color maps are available, to be assigned to different windows.

|> I'll be a SIGGRAPH next week so if anyone wants to discuss this, look for me. 
|> -- 
|> ---------------------------------------------------------------------------
|>  Jeff Hanson - Scientific Graphics Programmer and Workstation Administrator
|>  Sverdrup Technology, NASA Lewis Research Center Group
|>  NASA Lewis Research Center, MS 86-4, Cleveland, Ohio 44135
|>  Telephone - (216) 433-2284  Fax - (216) 433-2182
|>  tohanson@gonzo.lerc.nasa.gov	-   ViSC: Better Science Through Pictures

-- Kurt Akeley	    kurt@sgi.com  (415) 390-3612  M/S 7U-550
Newsgroups: comp.sys.apollo