Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!rutgers!usc!pollux.usc.edu!addison From: addison@pollux.usc.edu (Richard Addison) Newsgroups: comp.sys.amiga.tech Subject: Re: The Future of HAM Summary: While we're at it... Keywords: Overlay bit Message-ID: <19144@usc.edu> Date: 12 Aug 89 20:49:05 GMT References: <1579@psueea.UUCP> Sender: news@usc.edu Reply-To: addison@pollux.usc.edu (Richard Addison) Organization: University of Southern California, Los Angeles, CA Lines: 43 In article <1579@psueea.UUCP> bartonr@jove.cs.pdx.edu (Robert Barton) writes: > > jmdavis@cbnewsd.ATT.COM (j.michael.davis) writes: >> At 8 bits per pixel, a HAM mode will be able to DISPLAY 256K COLORS AT ONCE, >> with a base register table of 64 colors. (I know there are 256K pixels on a >> 512x512 screen, but you get the idea.) > > With 8 bits per pixel you would also need 18-bit color registers. This won't >work with the current 16 bit register size. A 7-plane mode would work if you >had 5-bit video DAC's. In other words: > >planes registers bits/reg colors > n 2^(n-2) (n-2)*3 2^((n-2)*3) > 6 16 12 4096 > 7 32 15 32768 > 8 64 18 262144 While we're at it, use 7 planes for HAM so that we have 5 bits per color component plus one bit for overlay for a total of 16 bits per color register. And, since it would be nice to have a real alpha channel, how about another HAM mode with 7 planes, and 4 bits per color component with the following encoding for the top 3 bits to determine to use of the lower 4 bits: Mode Meaning ---- ------- 0 0 0 Use color register n 0 0 1 Set Red component to n 0 1 0 Set Green component to n 0 1 1 Set Blue component to n 1 0 0 Set Alpha channel to n 1 0 1 Set Hue to n 1 1 0 Set Saturation to n 1 1 1 Set Value to n Note that this, too, uses 16 bits per color register (4 red, 4 green, 4 blue, and 4 alpha). Of course, these 4 alpha bits could be available in other video modes. Imagine the nice antialiased genlocking we could do with this! Richard Addison "Klein bottles for sale. Inquire within."