Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!ucsd!ames!sgi!shinobu!odin!krypton!gavin From: gavin@krypton.asd.sgi.com (Gavin A. Bell) Newsgroups: comp.sys.amiga Subject: Re: Better Amiga Graphics and HDTV Keywords: interactive programs, graphics Message-ID: <10445@odin.corp.sgi.com> Date: 17 Jul 90 02:52:05 GMT References: <3525@crash.cts.com> <1990Jul15.183009.21518@laguna.ccsf.caltech.edu> Sender: news@odin.corp.sgi.com Organization: Silicon Graphics, Inc. Mountain View, CA Lines: 53 In <1990Jul15.183009.21518@laguna.ccsf.caltech.edu> andrey@coil.caltech.edu (Andre T. Yew) writes: > Has anyone seen the Silicon Graphics Powervision series? I've heard >that some machines have up to 268 (268 -- not a typo) bits per pixel. Now, >what would one want to use 268 bits per pixel for? Well, I assume some of >it goes to Z-buffering, but the more interesting uses I've heard for it are >hardware texture mapping, hardware fog, and hardware motion-blur. For the curious, those 268 bitplanes are used for: 24 bits RGB, frontbuffer 8 bits alpha (used for transparency), frontbuffer 24 bits RGB, backbuffer 8 bits alpha, backbuffer (two buffers for smooth animation) 24 bits z-buffer (used for hidden-surface elimination) 8 bits stencil (used as a very sophisticated image mask, with which effects like computational solid geometry or or shadows may be done in real time) 96 bits for storage of texture maps (images to be mapped onto the polygons drawn) 64 bits for the 'accumulation buffer'. By adding together several images into the buffer (and later dividing by the number added), effects like motion blur, depth of field, and full-scene antialiasing are possible. 8 bits are a window identifier, used by the windowing system to keep track of which window is being drawn into (this allows no penalty for having multiple, arbitrarily shaped windows) and what display-mode each window is in. 4 bits used by the window manager to implement pop-up menus. ----- 268 bits/pixel * 1280 pixels high * 1024 pixels tall / 8 bits/pixel = about 43 megabytes of video ram dedicated to the display. You can buy a PowerVision system with 'only' 140 bits/pixel. Plus a lot of custom hardware to get the 1 million 3D triangles/second drawing rate. Fog is implemented as part of the 3D point transformation process (the color of each point in each polygon is blended to the fog color based on the distance of the point to the eye). True, this all costs more than $100K, but Silicon Graphics Personal Irises have started breaking the $10K price barrier, and prices will continue falling just as surely as Silicon Graphics will come out with something that will blow PowerVision away (in a few years...). --gavin -- --gavin (gavin@sgi.com, (415)335-1024)