Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!sharkey!itivax!abaa!esker From: esker@abaa.uucp (Lawrence Esker) Newsgroups: comp.sys.amiga.tech Subject: Re: The Future of HAM Summary: Extra extra extra half brite mode please. Message-ID: <1626@abaa.UUCP> Date: 23 Aug 89 19:16:36 GMT References: <1579@psueea.UUCP> <19144@usc.edu> <507@tardis.Tymnet.COM> <795@becker.UUCP> <21388@cup.portal.com> Reply-To: esker@uranus.UUCP (Lawrence Esker) Organization: Allen Bradley Lines: 79 In article <21388@cup.portal.com> FelineGrace@cup.portal.com (Dana B Bourgeois) writes: >Amiga Transactor had an article along these lines awhile back and at one >point the author pointed out that while the human eye cannot distinguish >16 million different colors, at least that many are necessary for lifelike >images because when color range is limited, a wide range of grayscale >is needed to keep the image realistic... >OK, doesn't this mean that the ultimate system would be 8 or more pixels >of RGB? 24 bits of color, 8 of alpha, 8 of direction (or one for HAM) is >still too many for a system in the Amiga market... No, what this means is that we need more control over the greyscale content of the colors we do have. Staying within practical limits and todays technology of cost verses performance, I will describe my ideal video system. First use a 8 by 32 bit color register. This will allow the user to choose from a pallete of 8 each RGB and 8 alpha. While 8 bit video D/A's are practical, expecting DMA and memory support for 24 bitplanes is impossible. Needs a very hefty (>$20k ?) pricetag. 256 simultaneous colors should cover all technical/presentation/CAD applications. Second, improve the extra half brite mode to three bits. Using 5 color bits and 3 intensity bits should cover most semi-realistic animation. This allows 32 separate colors with 8 shades _of each color_. Third, add software support for dithering. 32 colors on a 640 pixel line would appear to the eye as 1024 colors (32 real plus 32x31 pseudo). The software should let the user think he has a pallate of 1024 colors and the graphics library should map these into dithered colors. Special algorithms will be needed to do this right. Given a 4 pixel series, abcd, colors ab, bc, and cd are all virtual to the eye. We can't treat this as 2 pairs of virtual colors ab and cd and ignore the effect of bc. This would turn our 640 pixel line into 320 virtual pixels, destroying the realizm. Now I think 1024 colors at 8 shades of each colors would be TV level life like realism, even for stills. Fouth, add hardware support for simple edge enhancement and averaging techniques. For example, turning on averaging for the alpha bits may prevent some picket fence effects in genlocks when two pixels with drastically different alpha values are side-by-side. (An example would be 25 % previous + 50 % current + 25 % next alpha values added together.) Turning on edge enhancement for the intensity bits would allow detail in a picture to stand out while preserving the color purity. (An example would be -25 % previous + 150 % current - 25 % next pixel.) Turning on averaging for the intensity bit would provide a pastel like effect. Either of these effect would cause an 32 virtual levels of shade for 1024 virtual pixels. Needs a five position barrel shift on each of the 8 RGB outputs. Finally, throw out HAM as we know it today. A waste of ASIC real estate. :-) As Dana pointed out, the eye readily sees changes in intensity, but tends to average color content together. But HAM, to do an intensity change, requires three pixels causing massive color fringing where there is simple changes in intensity of a given color. Actually, change HAM to use three control plus 5 data bits (8 bitplanes). The three control bits would select the color register of 32, change one of the three colors, change an intensity multiplier, change the alpha field, or two other features. Of coarse, this whole discussion assumes 8 bit planes at a 640 pixel line resolution. Also assumes 8 bit video D/A's. Tough, slightly expensive, possible with todays technology, and as realistic to the human eye as we will ever need. > ...But someday all >computers will have relistic color images in the Amiga price range. Even >I*M! > >Dana No, the I*M never will, it would have to be upward compatible with their current primative offerings. This is impossible :-). ---------- Lawrence W. Esker ---------- Modern Amish: Thou shalt not need any \ * * * ******* / computer that is not IBM compatible. \ * * * * * / \ * * * * * ***** / Sr. Hardware/ASIC Design Engineer \ * * * * * * / Allen-Bradley Communications Div. \ ******* * * ******* / Work: (313)668-2500 Home: (313)973-8561 ----------------------------- Compuserve: 76337,2524 UseNet Path: __!uunet!mimsy!rutgers!citi!itivax!abaa!esker