ken (02/22/83)
From: decvax!harpo!utah-cs!jwp I used color-map animation, to (what else?) make animated films. Actually, the color map animation was used as a preview mechinism for the real filming, which was done using shaded 3D imagery and was two slow for real time. Traditional technique; by writing each frame in each available color and then turning each color "on" in sequence by telling the color map that the color is white and all others are black. There are some problems with this, one of them being that if the movement is very slow the "black" parts of some frames will overwrite earlier frames. Thus things at the beginning of the sequence tend to look rather ratty. To get around this, I also used "Pan" animation, meaning the frames were distributed sequentually in each quadrant of the screen. By using a zoom magnification factor of *2 (so only 1/4 of the screen shows at once) and changing the origin, frames are shown in sequence. By writing one set of four frames in one "color", the next set of four in the next "color", etc, you can make a pretty good improvement towards eliminating overwrite. (Also I should mention the frame buffer used was only eight bits deep, so images were restricted to black and white line drawings. This was part of the "INCAS" animation system done at Oregon Software). So much for my hacking. For a serious investigation of using frame buffer/color map/zoom-pan/etc. tricks, you'll want to get a copy of Dino (real name is Dennis, I think) Schweitzer's PhD thesis, currently in progress here at the U of Utah. (I think he plans to finish this summer, but don't quote me on that). He has done a lot of research on how to improve visual perception using frame buffer techinques, ranging from color-map animation to the use of shading and transparency. I've seen some pretty impressive things done with it, e.g. fully rendered surfaces moving about in real time on non-megabuck hardware. Several other of the utah graphics people (The Alpha_1 computer-aided design group, to be exact) have come up with similar techinques, e.g. using color map animation to make it appear as though the light source in an image is moving as you twist a knob. You may also want to check out the "SHAZAM" animation system done by the folks out at Xerox-PARC during the mid 70's (I think this was the SmallTalk/LRG group, I may be able to dig up a referance). jw-peterson p.s. I'm also quite interested in this type of stuff...pls post the responses. ****************************************************************************** From: decvax!yale-comix!brunix!foxvax1!cascio Steve Feiner at Brown University (brunix! ? ) has done a lot of work in animation. He has developed a unique music score-like notation for orchestrating the simultaneous movements of different things on the screen. See IEEE Computer Graphics and Applications, Sept. 82. Many of these techniques are based on color table manipulation, if I'm not mistaken. Joe Cascio The Foxboro Co. (foxvax1!cascio) ****************************************************************************** To: seismo!harpo!decvax!decwrl!turtleva!ken Yes, we here at U. of Rochester have done so. It is even published in (I think) Computer Graphics and Image Processing about four years ago. We used it to animate a globe spinning and also as an aid in Star Wars game. =lee ****************************************************************************** From: burdvax!hdj I know of one commercial c.g. system that makes (made?) heavy use of color table animation. It is described by Dick Shoup in the 1979 or 1980 Siggraph Proceedings, and was sold for a while by his company, called Aurora. I think Ampex marketed it, too, or had something similar. Herb Jellinek, burdvax!hdj ****************************************************************************** >From decwrl!decvax!yale-com!brunix!skf Wed Feb 9 13:27:56 1983 See Dick Shoup's paper, Color Table Animation, in Computer Graphics 13:2 (Proc Siggraph '79), for a good explanation of the standard color table animation tricks. Color table animation is a widely touted feature of the commercial paint systems being sold to television stations. Limited? True, but we've used color table animation (on raster systems with slow pixel write times that make it impossible to draw big things fast) for movie marquee style cycling arrows, a variety of blinking effects in which colors smoothly fade from one to the other, fading up/down images, etc. Other animation effects may be obtained in combination with the hardware pan and zoom instructions provided on many raster systems. For example, in a 1280x1024 8 bit deep frame buffer, one might draw 128 320x256 1 bit deep images. These may be viewed in rapid sequence by zooming up 4 times and panning through the 16 images on each plane, changing the color lookup table as each new plane is inspected, so that plane's bit alone determines the color of a pixel. At 15 frames per second, that's over 8 seconds of animation. Other variations include using several bit deep multicolor images, mixing image size and depth, varying the amount of time spent on each, introducing local image loops, and employing some additional color lookup table effects (or actual drawing) when displaying some of the images. These techniques have been invaluable for previewing movie animation and can serve as a useful supplement to a vector system when there's a need for shading or hidden line removal, or image/object modifications that just can't be done in real time. Steve Feiner {decvax,vax135}!brunix!skf skf.brown@udel-relay ****************************************************************************** >From ken Thu Feb 10 22:05:53 1983 Thanks for your response to my question about color map pseudo-animation. Tom Duff pointed out that KRON-TV here in the San Francisco Bay Area uses Dick Shoup's Aurora system quite a bit during the news and sports events. Dick markets the machine as a cheap vehicle to do animation with, and KRON actually does use the psuedo-animation capabilities of the color map for interesting effects, such as moving flames in the over-the-shoulder picture above the newscaster as he tells about a fire. They also use the paint capability of the system to draw on the weather map. I was asking the question because the question came up in my work as to whether color maps should be loadable in the vertical interval. So far I haven't been able to come up with a good reason except that "everyone" else does it. Ken Turkowski ucbvax!decwrl!turtlevax!ken ****************************************************************************** From: Liudvikas.Bukys Eugene Ball's StarWars, a Death-Star simulation, ran on a Xerox Alto communicating over a 3Mb Ethernet to a Grinnell GMR26 on a Data General Eclipse. It used the GMR's color map for double (or triple?) buffering. (His most famous game creation was Alto StarTrek. Well known to Alto users, it was pictured (without credit) in an illustration in Byte Magazine once.) There was an article by Ken Sloan and possibly Gene Ball in some journal on the subject of color maps. I believe StarWars is even one of the illustrations. I can dig up the reference if you like. Liudvikas Bukys rochester!bukys ****************************************************************************** From: decvax!watmath!watcgl!dmmartindale One very useful technique is to use reserved colours for things like menus, and then stuff colour map entries to make them appear and disappear instantly as the user does various things. This isn't as good as having a crossbar switch between your frame buffer and lookup tables since the crossbar lets you have overlapping menus without worrying about handling intersections of various menus, but lots more available hardware has lookup tables than a crossbar.
skf (02/22/83)
In response to Ken's question about when to load the color lookup table: If the color lookup table can't be loaded during vertical retrace, then some objects may have their top parts displayed in their previous colors and their bottom parts in their newly set colors. To make matters worse, if a table entry is being changed in rapid succession (to accomplish a fade) and the graphics system provides no ability to sync the changes with the video then the point of color change may even occur at a different video line in each frame (very visually unsettling!). Steve Feiner decvax!brunix!skf skf.brunix@udel-relay
lee (02/23/83)
Actually, the real reason that you want to load the look-up table during retrace is to eliminate contention for the look-up table memory. We have a Grinnell 27 and it doesn't load at that time and so there is contention which shows up as snow on the image for brief periods. Very distracting if you are trying to do animation and are thus changing the table continuously. =lee (seismo or allegra)!rochester!lee