Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!think.com!paperboy!hsdndev!husc6!genrad!stardent!jch From: jch@Stardent.COM (Jan Hardenbergh) Newsgroups: comp.graphics Subject: Re: Practical Intro to PHIGS (new book) Message-ID: <1991Apr19.175910.2922@Stardent.COM> Date: 19 Apr 91 17:59:10 GMT Organization: Stardent Computer, Concord MA Lines: 123 > From: levine@well.sf.ca.us (Ron Levine) > Jan Hardenbergh reviews the new book on PHIGS and PHIGS PLUS on > the basis of an all too cursory inspection: I stand by my characterization that this book is great. I've had another few days to look at it, too. I do concur with Ron Levine in that the does not go into lots of detail in many places. But it is a 339 page book - including lots of appendices and examples. I too was disappointed with the failure to call out UQUM (Yookum?) as an important interactive feature. As for the NURBS stuff, I'm still wading through the Piegl article in January's IEEE CG&A. That is the first one that I've felt like all I have to do is reread it a few times and I will get it. So, I can't cast stones - But the one example Ron cites is broken according to my humble understanding. While Ron brings up some good points, he is too is human. > Further, I think it is confusing and very bad to > place the discussion of "dynamic modification accepted" in Sec. > 8.3, before the discussion of deferral mode and quick update. > And, in my opinion, the definition of "implicit regeneration" in > this section is just wrong. (The PHIGS standard uses the term > but never precisely defines it). The whole discussion fails to > mention the all-important point that traversal, or regeneration, > is generally needed to be sure that the picture is correct, no > matter what the output device is. While the definition of "implicit regeneration" is a little clumsy in its English, it is true. And the PHIGS spec does indeed explicity define implicit regeneration. ANSI X3.144-1988 page 10. 3.89 implicit regeneration: The complete recreation of the contents of a display surface such that . Such a regeneration is not explicitly requested by the application program. While this is not a good explanation and people tend to think this can happen at any time (which it cannot) it is defined. The book does include the flow chart from the spec which is much better than any words. As for the weak treatment of PHIGS-PLUS, well, seeing as 10 new primitives were added at about the same time the book was going to press, I'd say the authors are excused for not going into detail on everything. It does have enough to get started - which is more than anything else. I thought the sections on lighting and shading were good. If you have trouble remembering lighting and shading, this of shading as applying different shades of color to an object.(shading==interpolation) It is hard for me to believe that a book could have as much detail as Ron Levine wants and still be an introductory book. I made it quite plain in my first posting that it was not "a reference book on all of the details and issues". I suspect such a book would be at least twice the size. > From: levine@well.sf.ca.us (Ron Levine) > Jan Hardenbergh reviews the new book on PHIGS and PHIGS PLUS on > the basis of an all too cursory inspection: I stand by my characterization that this book is great. I do concur with Ron Levine in that the does not go into lots of detail in many places. But it is a 339 page book - including lots of appendices and examples. I too was disappointed with the failure to call out UQUM (Yookum?) as an important interactive feature. As for the NURBS stuff, I'm still wading through the Piegl article in January's IEEE CG&A. That is the first one that I've felt like all I have to do is reread it a few times and I will get it. While Ron brings up some good points, he is too is human. > Further, I think it is confusing and very bad to > place the discussion of "dynamic modification accepted" in Sec. > 8.3, before the discussion of deferral mode and quick update. > And, in my opinion, the definition of "implicit regeneration" in > this section is just wrong. (The PHIGS standard uses the term > but never precisely defines it). The whole discussion fails to > mention the all-important point that traversal, or regeneration, > is generally needed to be sure that the picture is correct, no > matter what the output device is. While the definition of "implicit regeneration" is a little clumsy in its English, it is true. And the PHIGS spec does indeed explicity define implicit regeneration. ANSI X3.144-1988 page 10. 3.89 implicit regeneration: The complete recreation of the contents of a display surface such that . Such a regeneration is not explicitly requested by the application program. While this is not a good explanation and people tend to think this can happen at any time (which it cannot) it is defined. The book does include the flow chart from the spec which is much better than any words. As for the weak treatment of PHIGS-PLUS, well, seeing as 10 new primitives were added at about the same time the book was going to press, I'd say the authors are excused for not going into detail on everything. It does have enough to get started - which is more than anything else. The charge that this was rushed to market is spurious. It sets a very high standard for PHIGS books. I'd like nothing better than to see all of the PHIGS books be better, but I'm not going to hold my breath. I thought the sections on lighting and shading were good. If you have trouble remembering lighting and shading, this of shading as applying different shades of color to an object.(shading==interpolation) It is hard for me to believe that a book could have as much detail as Ron Levine wants and still be an introductory book. I made it quite plain in my first posting that it was not "a reference book on all of the details and issues". I suspect such a book would be at least twice the size. -- -Jan "YON" Hardenbergh jch@stardent.com (508)-371-9810x261 Stardent Computer, 6 N.E. Tech Center, 521 Virginia Rd,Concord, MA 01742