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From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga,comp.sys.amiga.tech,comp.sys.amiga.hardware
Subject: Re: Retargetable graphics. Temporary Stop-gaps.
Summary: Multiple sets of bitplanes
Keywords: rtg,iff,24bit,video hardware
Message-ID: <1402@tardis.Tymnet.COM>
Date: 7 Jan 91 21:02:21 GMT
References: <12437@life.ai.mit.edu> <16612@cbmvax.commodore.com> <7307@sugar.hackercorp.com> <1990Dec20.164538.24027@jarvis.csri.toronto.edu>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: BT Tymnet, San Jose, CA
Lines: 37

In article <1990Dec20.164538.24027@jarvis.csri.toronto.edu> kevins@dgp.toronto.edu (Kevin Schlueter) writes:
>2D graphics:  window and gadget imagery and the graphics found in
>  draw programs, basic paint programs and other common apps.  These
>  programs require  bitblt and its relatives, rectangle/polygon draw/fill,
>  flood fill, pattern fill, optimized text display routines, etc).
>3D graphics: 3-D modelling and animation programs, primitives to support
>  3D affine transformations, complicated clipping, various types of
>  shading/illumination models, and texture mapping.  
>
>Often, when designing a framebuffer, you make tradeoffs that favour one
>type of graphics over the other, in order to keep costs down.  For this
>reason, we should consider whether we need to run _all_ applications on
>fancy 24 bits frame buffers or whether we should make 24 bit displays that
>are optimized for modelling and animation.

I've noticed that Sun has looked into this problem with their SPARCstation
2GT workstation, and decided not to compromise, and instead implemented both.
The 2GT has 108 bitplanes!

Two sets of 24 bits for doing double-buffered 24-bit true color.
Two sets of 8 bits for 256-color overlays.  (This allows pop-up menus to
be rendered without disturbing the 24-bit image below it.)  Two planes for
hardware cursor; one to enable, the other to select one of two colors.
Plus various other enable planes, 24-bit Z buffer, hardware window clipping.

My point is: when designing a high-performance deep-pixel video card that
will be used in a windowing environment, manufacturers should consider
implementing 24+N bits per pixel.  The extra +N bits are for showing
things like window borders, menus, and other overlayed graphics.

I wonder how many companies designing video cards for the Amiga are working
on more than 24 bits.
-- 
Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com
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