Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!decwrl!mcnc!borg!sargent!cullip From: cullip@sargent.cs.unc.edu (Timothy Cullip) Newsgroups: comp.sys.amiga.graphics Subject: Re: Colorburst and Animation Message-ID: <2325@borg.cs.unc.edu> Date: 15 Mar 91 21:41:40 GMT References: <13948@life.ai.mit.edu> <1991Mar15.193235.2926@cs.mcgill.ca> Sender: news@cs.unc.edu Organization: University of North Carolina, Chapel Hill Lines: 31 In article <1991Mar15.193235.2926@cs.mcgill.ca> tinyguy@cs.mcgill.ca (Yeo-Hoon BAE) writes: > >One thing I always wondered about 24bit cards: > > Is it really necessary to use all 24 bits? > From quick calculation, 18 bits are more than enough to > display 640x400 screen with every pixel having different > colors. So why not have 24 bit palettes and use 18 bits > or less for the lower resolutions? This should give some > improvements to the overall animation performance... > > The problem is that with 24 bits you have true color and don't need a color lookup table (or palette as you would call it). The 24 bits directly define the color. If you wanted say an 18 bit frame buffer with a palette of 24 bit entries you need 2^18 entries (each 3 bytes). Now the 18 bits don't directly define the color but rather an address into the palette that holds the color (indirect color). This is 7.8 Mbytes for the palette table. So now your palette table is larger than your frame buffer! Most people don't use palette tables above for frame buffers above 16 bits but rather go with true color. -- Tim Cullip cullip@cs.unc.edu