Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!seismo!ut-sally!utah-cs!utah-gr!uplherc!esunix!nelson From: nelson@esunix.UUCP Newsgroups: comp.graphics Subject: Re: effective resolution and anti-aliasing Message-ID: <347@esunix.UUCP> Date: Wed, 10-Jun-87 16:03:27 EDT Article-I.D.: esunix.347 Posted: Wed Jun 10 16:03:27 1987 Date-Received: Sat, 13-Jun-87 09:35:38 EDT References: <1713@ames.UUCP> Organization: Evans & Sutherland, Salt Lake City, Utah Lines: 52 in article <1713@ames.UUCP>, lamaster@pioneer.arpa (Hugh LaMaster) says: > > I have heard that it is possible to represent lines of less than 1 pixel in > width with greyscale or color images using data filtered from a higher > resolution image or object. I have never seen either the algorithms or the > theoretical basis for an algorithm. [An example would be a representation, > using a greyscale picture, of a line less than one pixel or dot width in size]. > I have looked in standard graphics textbooks and find no mention of this [but > I could have missed something or not understood what I was looking at]. Does > anyone know of any references for this? Are there any devices out there which > make use of it [e.g. a monitor with a much higher resolution frame buffer than > the tube and a filter to reduce the resolution before output to the tube]? > > Hugh LaMaster, m/s 233-9, UUCP {seismo,topaz,lll-crg,ucbvax}! > NASA Ames Research Center ames!pioneer!lamaster > Moffett Field, CA 94035 ARPA lamaster@ames-pioneer.arpa Disclaimer: Please don't take this as a sales pitch, it is intended for information only. There is one line drawing system currently on the market with a much higher effective resolution than the actual screen resolution. This is the Evans & Sutherland PS 390. The visible portion of the frame buffer is 1024 x 864 pixels with the line filtering occurring when the lines are drawn into the frame buffer. The effective resolution is 8192 x 6912. I and several other engineers here have done extensive research on anti-aliasing techniques and we know of no literature (available outside of our company :-> ) on this subject. Most of what I have seen on anti-aliasing lines is actually misleading. The usual methods in the top computer graphics books have roping on the lines which causes moire patterns when lots of lines are together and some temporal aliasing effects when lines are moved slowly. I have personally seen lines moving by only 1/8 of a pixel on a PS 390 where the motion could be seen with the unaided eye. On this machine, the higher effective resolution applies to line positioning but not to line width. To get lines with an actual effective line width of less than one pixel you will have to buy a CT-6. :-) ----- Scott R. Nelson Evans & Sutherland Computer Corporation UUCP Address: {decvax,ucbvax,ihnp4,allegra}!decwrl!esunix!nelson Alternates: {ihnp4,seismo}!utah-cs!utah-gr!uplherc!esunix!nelson seismo!usna!esunix!nelson "Smooth lines, they're not just for vector displays anymore."