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- Newsgroups: comp.windows.x.pex
- Path: sparky!uunet!orca!mesa!rthomson
- From: rthomson@mesa.dsd.es.com (Rich Thomson)
- Subject: Re: Future development of PEX/PHIGS
- Message-ID: <1992Aug16.172124.15631@dsd.es.com>
- Sender: usenet@dsd.es.com
- Nntp-Posting-Host: 130.187.85.21
- Reply-To: rthomson@dsd.es.com (Rich Thomson)
- Organization: Design Systems Division, Evans & Sutherland, SLC, UT
- References: <1992Aug13.170434.18221@hsr.no> <5759@m1.cs.man.ac.uk>
- Date: Sun, 16 Aug 92 17:21:24 GMT
- Lines: 51
-
- In article <5759@m1.cs.man.ac.uk>
- lilleyc@cs.man.ac.uk (Chris Lilley) writes:
- [on anti-aliasing]
- >The Evans&Sutherland implementation has had antialiasing for a while.
- >The DEC implementation supports it only on harware that supports it.
- >Both do it as escapes. There is no support for antialiasing in the ISO
- >standard.
-
- There is no explicit support, but that doesn't mean that the
- renderings are guaranteed to be aliased, either. A PHIGS
- implementation could render all of its primitives anti-aliased and it
- wouldn't be in violation of the standard. What is missing are
- controls for changing the amount of anti-aliasing performed. We
- provide full anti-aliasing on all line-based primitives (polymarkers,
- polylines, stroke text) by default. You can turn this off if it is
- desired via a GSE that we provide. Escapes are a different mechanism
- used to modify global behavior of a workstation; using a GSE allows
- hierarchical control of the "aliasing" attribute in a structure.
- Some line-based primitives in a structure may be aliased while others
- are anti-aliased, depending on where the GSE is placed in the
- structure (or issued in immediate-mode).
-
- Full support for anti-aliasing could be quickly introduced into PHIGS
- if all the vendors agreed on a particular format for a GSE data record
- and registered this record with ISO. Registration is a fairly quick
- process and doesn't need any voting to take place in order to be
- accepted. Portability can be maintained if the vendors work
- cooperatively to support and register such a GSE. If you, as an
- application programmer or user, desire such support from your vendor,
- please ask them to support such a cooperative registration.
-
- PHIGS can be extended in many ways via registration without having to
- go to the standards committee and get a full-vote for approval. In
- this way, vendors can improve and extend upon the basic
- PHIGS/PHIGS-PLUS definition. The temptation is for each vendor to "go
- their own way" and provide features only in their implementation not
- available in other implementations so that they can define themselves
- as having a competitive edge. This, of course, leads to portability
- problems. The best way to alleviate those portability concerns is for
- vendors to register their extensions (thus allowing other vendors to
- simulate/emulate them if possible) and for users to impress upon
- vendors how much they care about portability. Companies generally
- listen to their customers (and if they don't, they deserve what they
- get I suppose).
-
- -- Rich
- --
- Repeal the personal income tax; vote Libertarian in 1992.
- Disclaimer: I speak for myself, except as noted; Copyright 1992 Rich Thomson
- UUCP: ...!uunet!dsd.es.com!rthomson Rich Thomson
- Internet: rthomson@dsd.es.com IRC: _Rich_ PEXt Programmer
-