Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!stanford.edu!msi.umn.edu!umeecs!zip!spencer From: spencer@eecs.umich.edu (Spencer W. Thomas) Newsgroups: comp.graphics Subject: Re: Practical Intro to PHIGS (new book) Message-ID: Date: 24 Apr 91 19:23:19 GMT References: <1991Apr19.175910.2922@Stardent.COM> <24373@well.sf.ca.us> Sender: usenet@zip.eecs.umich.edu (Mr. News) Organization: University of Michigan EECS Dept Lines: 19 In-Reply-To: levine@well.sf.ca.us's message of 23 Apr 91 09: 18:41 GMT In article <24373@well.sf.ca.us> levine@well.sf.ca.us (Ron Levine) writes: > The second sentence overlooks the fact, that in general, NO > workstations have the ability to modify parts of a displayed > picture selectively, at least not correctly. On a CRT, you can > delete a primitive by painting it out in the background color, > but in general you will not produce a correct picture because you > will damage whatever primitives lie under the deleted one. Not true. Many high-end workstations have a "built-in" display list. Thus, as far as PHIGS is concerned, the image can be correctly modified selectively. An old example is the E&S PS300 series (not sure about their new workstation, as I don't have one.) Even on a "bit-mapped" workstation, it may be possible to selectively update an image, under certain conditions - for example, when adding a new primitive to the end of a structure (depending on structure priority). -- =Spencer W. Thomas EECS Dept, U of Michigan, Ann Arbor, MI 48109 spencer@eecs.umich.edu 313-936-2616 (8-6 E[SD]T M-F)