HDTenEightyP/NetNews huggingface dataset:
From: ledwards@leland.Stanford.EDU (Laurence James Edwards)
Subject: Re: Converting polygon with concave boundary to convex one anybody?
Organization: DSG, Stanford University, CA 94305, USA
Date: Tue, 28 Jul 92 22:15:18 GMT

In article <9207281143.AA27417@ucbvax.Berkeley.EDU>, S.Marshall@sequent.cc.hull.ac.uk (Simon Marshall) writes:
|> Hi all.  I mailed this question a while back, but shortly after the machine I
|> read news on hiccuped for a couple of days, and now I find out that our mailer
|> fails, with a loss of incoming mail, on a regular basis.  If you've responded
|> once, please do again, sorry!
|> 
|> I have a group of planar polygons with concave boundaries.  I wish to replace
|> each of these polygons with a number of triangular ones.  For a polygon with a
|> convex boundary, it's quiet easy.  All I do is pick a single polygon vertex and
|> form triangular facets, using this vertex, with successive pairs of vertices
|> around the polygon boundary.  The single polygon vertex is therefore common to
|> all triangular facets.
|> 
|> This, of course, will not work for polygons whose boundaries are concave, since
|> a triangular facet may lie outside the boundary of the polygon.  So either I
|> must use a different method of generating triangular facets, or firstly
|> generate polygons with convex boundaries from the polygons with concave
|> boundaries.
|> 
|> The $64M question is, how do I convert a concave polygon to a convex one?  I
|> thought there was a solution to this in Graphics GEMS, but nope...

Just Delauney triangulate the thing, throwing out edges that lie outside the
polygon ... i.e. connect each vertex to its nearest neighbor, but only if the
edge does not leave the polygon. This will leave you with a bunch of triangles
and possibly some convex regions. Split up the convex regions using your
old method.

The most straight forward way to do this is recursion ... go through the
list of vertices for a polygon, when you find a vertex that you
can connect to its nearest neighbor split the polygon and apply the
same procedure to the 2 new polygons. If there are no vertices in the 
polygon that can be connected to their nearest neighbor, then the polygon
is convex and you can split it up with your old method and return.

Larry Edwards
edwards@sunrise.stanford.edu
Newsgroups: comp.graphics
From: mann@intacc.uucp (Jeff Mann)
Subject: Re: NAPLPS graphics code or specs
Date: Mon, 20 Jul 1992 19:24:36 GMT
Organization: Inter/Access' Matrix BBS

In article <l5shg3INNnci@exodus.Eng.Sun.COM> hess@suntea.Eng.Sun.COM (Marty Hess) writes:
>In article <uN2kNB2w164w@uuisis.isis.org> mpdillon@uuisis.isis.org (Michael Dillon) writes:
>>Does anybody know where I can find C source code and/or specifications
>>for a graphics format known as NAPLPS (North American Presentation
>>Level Protocol Syntax) and formerly known as Telidon in it's
>>Canadian incarnation. This is an object-oriented graphics format
>>specifically designed for efficient telecommunication of graphics
>>in the late 70's and early 80's. I believe it is currently used
>>to some extent by Prodigy in the US and Minitel in France.

Prodigy yes, Minitel no. Also Bell Canada's ALEX system uses it. You can
rent a NAPLPS terminal from the phone centre for about ten bucks a month.

>  From		Standard #
>
>  ISO		2022-1982
>  ANSI		X3.41-1974
>  CSA		Z243.35-1976

I've got a more recent publication, CSA T500-1983 and ANSI X3.110-1983,
it's a joint publication.  You also might want to talk to MicroStar in
Ottawa, Canada.  They have a NAPLPS graphic creation/editor package, as
well as a terminal program.  Both are good products, and have recently
been released as shareware.  You might also want to talk to Dave Hughes
in Old Colorado City (Colorado Springs).  He is "Mr. NAPLPS" - (719) 636-2040.

P.S. e-mail me and tell me about what you're doing...

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
|  Jeff Mann  Inter/Access Artists' Computer Centre, Toronto  [416] 535-8601 |
| ...uunet!intacc!mann   intacc!mann@cs.toronto.edu  mann@intacc.uucp        |
|      The Matrix Artists' Computer Network BBS: [416] 535-7598 2400 8N1     |
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
From: reuel@blivet.houst.sgi.com (Reuel Nash)
Newsgroups: comp.graphics
Subject: Re: Graphics Gems
Date: 23 Jul 92 16:26:38 GMT
Reply-To: reuel@blivet.houst.sgi.com (Reuel Nash)
Organization: Silicon Graphics Inc., Mountain View, CA


In article <8242@amsaa-cleo.brl.mil>, neiderer@amsaa-seer.brl.mil
(Andrew Neiderer ) writes:
|> 
|> Can anyone tell me why some vector functions, such as 
|> 
|> Vector2 *V2Add(a, b, c)
|> Vector2 *a, *b, *c;
|> {
|>         c->x = a->x+b->x;  c->y = a->y+b->y;
|>         return(c);
|>         };
|> 
|> return the pointer to the resultant vector.  I would 
|> just declare it as void since c already contains the
|> answer.  There must be some advantage to doing it this way.
|> I looked throughout the Graphics Gems source code, and
|> found that this particular function is used, e.g. as
|> 
|> V2Add(&bezCurve[0],V2Scale(&tHat1, dist),&bezCurve[1]);
|> 
|> Sorry if this appears to be a C question.  My reason for 
|> posting here is to get the attention of some graphics 
|> programmer who uses this stuff.  Thanks.

The answer is hidden in your own example.
I'm assuming that V2Scale is:

Vector2 *V2Scale(Vector2 *a, float b)
{
	a->x *= b;
	a->y *= b;
	return a;
}


If it were declared as:

void V2Scale(Vector2 *a, float b)

you'd have to code the example as:

V2Scale(&tHat1, dist);
V2Add(&bezCurve[0],&tHat1,&bezCurve[1]);

which is a bit inconvenient. However, coding it this way does make it more 
clear that the argument is modified by the subroutine.



Reuel Nash				Email:	reuel@sgi.sgi.com  
"Question Skepticism"			Phone:	713-293-9292 (new)
USMail:	 Silicon Graphics, 11490 Westheimer Suite 100, Houston, TX  77077
Newsgroups: comp.graphics
From: kaustine@nbrwh34.bnr.ca (Mathew Kaustinen)
Subject: Re: Hidden Surface Removal
Organization: Northern Telecom, Bramalea, Canada
Date: Fri, 31 Jul 92 14:00:57 GMT

In article <1992Jul30.142742.5874@tc.cornell.edu> elan@tasha.cheme.cornell.edu (Elan Feingold) writes:
>
>to front, but this doesn't seem to work allways for me.  Example:
>
>
>
>            --\ 
>           / / \
>          / /\--
>         / / 
>         --
>
>I don't know if this picture is enlightening. :)  Basically I have a long
>polygon and then a smaller one going behind it.  When the viewpoint is slightly
>above and to the right of the scene, the longer polygon is plotted first,
>messing up the scene.  Can anyone help as far as an algorithm is concerned?

Just a thought (I lay awake half the night thinking about it!). Are
the co-ordinates of your patches ordered in the same direction? ie.
if you look "above" each patch do the points always rotate in the
same direction, such as:

             1a---2a 1b---2b
             |    |  |    |        Patches A and B have same "rotation"
             | A  |  | B  |
             |    |  |    |
             4a---3a 4b---3b
If not this may be your problem.
If so, since the patches are non intersecting, I think that a algorithm
that checks the z-distance for the same point # on each patch should
work.  I used this method on a Bezier surface program I wrote and it
seemed to work for this application.
-- 
Mathew A. Kaustinen          |      ESN:   (333) 2066
Field Service Engineering    |      PHONE: 416-452-2066
Northern Telecom, Bramalee   |      PAGER: 416-378-3246
Newsgroups: comp.graphics
From: reyb@TorreyPinesCA.ncr.com (Rey Berin 3791)
Subject: satellite image wanted
Organization: NCR (Torrey Pines Development Center)
Disclaimer: This posting does not neccessarily reflect the opinions of NCR.
Distribution: na
Date: Wed, 29 Jul 92 18:23:56 GMT

Hi,
	I'm playing around with putting up images under X 
and I would really like to get a cool looking satellite
image.  Anybody have one that they would like to e-mail
me? :)

Thanks,

Rey
=============================================================
 Rey Berin
 NCR Corporation                  (619) 597-3791 (voice)
 11010 Torreyana Road             (619) 597-3502 (fax)
 San Diego, California 92121      rey.berin@sandiego.ncr.com
=============================================================
From: mdf+@cs.cmu.edu (Mike Fox)
Newsgroups: comp.graphics
Subject: re: foley & co. errata file
Date: 22 Jul 92 20:28:50 GMT
Article-I.D.: cs.1992Jul22.202850.221911
Distribution: comp.graphics
Organization: School of Computer Science, Carnegie Mellon


Once again I got the answer I needed. The way to get the errata file, or
other info as shown below is to send email to graphtext@cs.brown.edu
containing a keyword (and only the keyword) in the "Subject:" line.  Only
one service can be obtained per message. Some of the more useful looking
keywords follow.  Thanks again for the help which I received.


Subject: Help

        The server sends you this helpful message in response.
        If the server program seems to be broken somehow, send mail to
                Dave Sklar (dfs@cs.brown.edu)
----------------------------------------------------------------------------
Subject: Get-Text-Bug-List

        Use this service to obtain a list of known "bugs" in the text.
----------------------------------------------------------------------------
Subject: Report-Text-Bug

        Use this service to report a bug in the text.  The body of your
        message should give the page and line number of the bug, and if
        possible, indicate the necessary correction to be made.

----------------------------------------------------------------------------
Subject: Get-Text-Algorithms

        Use this service to get instructions on how to obtain electronic
        copies of many of the major algorithms (all in Pascal) presented
        in the textbook.
----------------------------------------------------------------------------
Subject: Software-Distribution

        Use this service to get instructions on how to obtain SRGP and
SPHIGS,
        the software packages described in chapters 2 and 7.
        These include information on all three versions:
                1) UNIX/X11  (available via ftp)
----------------------------------------------------------------------------
Subject: Get-Software-Bug-List

        Use this service to obtain a list of known "bugs" in SRGP/SPHIGS.
        This list does not include omissions and bugs that are
        documented in the SRGP/SPHIGS reference manuals.
----------------------------------------------------------------------------
Subject: Report-Software-Bug

        Use this service to report a bug in the software or in the doc
        associated with the software.  If you can present a code fragment
        that isolates the bug, all the better.
----------------------------------------------------------------------------
Xref: sparky comp.graphics:8037 comp.os.ms-windows.apps:1427
From: IFF291@DJUKFA11.BITNET (Stephan Petersen)
Newsgroups: comp.graphics,comp.os.ms-windows.apps
Subject: Address of COREL wanted...
Date: 22 Jul 92 18:56:53 GMT
Organization: KFA  Forschungszentrum Juelich


I'm looking for the address of COREL Systems in Ontario, Canada.
If anybody out there knows, could you please drop me a line? (Also, fax
numbers and email addresses would be very helpful.)

(I'd like to enquire about their UNIX version of Corel Draw, btw.
There isn't by chance anybody from COREL out there listening :-) ?)

Thanks for any pointers,

Stephan


+------------------------------------------------+
| Stephan Petersen                               |
|                                                |
| Bitnet/EARN: IFF291@DJUKFA11                   |
| Internet:    IFF291@zam001.zam.kfa-juelich.de  |
+------------------------------------------------+
Newsgroups: comp.graphics
From: deb@cs.cornell.edu (David Baraff)
Subject: Re: Fast intersection DETECTION for convex polyhedra?
Organization: Cornell Univ. CS Dept, Ithaca NY 14853
Date: Thu, 23 Jul 1992 21:33:47 GMT

sundar@fiber-one.ai.mit.edu (Sundar Narasimhan) writes:

>In article <jqsx0dj@rpi.edu>, wrf@ecse.rpi.edu (Wm Randolph Franklin) writes:
>|> 
>|> In article <1992Jul9.134621.20715@fel.tno.nl> on Thu, 9 Jul 92 13:46:21 GMT,
>|> rxkc2@fel.tno.nl (R. Kiel) writes:
>|> 
>|>   > For a real-time visualisation system I need an algorithm that will
>|>   > tell me whether or not two convex polyhedra intersect.
>|> 
>|> A separating plane for the two polyhedra exists iff they don't
>|> intersect.  This can be formulated as a linear programming problem and
>|> solved.  It should be reasonably fast.
>I don't know if I responded to this already, but Lin and Canny's algorithm
>is the fastest (and easiest to implement) I know of currently.
>I'd like to hear if people know of others. (WRT approximation algs., the
>ellipsoidal approximation of Elon Rimon, and Featherstone's 'swept bubble' 
>sphere approximation should also be pretty fast).

At the risk of being self-promoting, check out
the article "Curved Surfaces and Coherence for Non-penetrating
Rigid Body Motion", in the 1990 SIGGRAPH conference proceedings.
A discussion of convex polyhedra is covered in that paper.

	David Baraff
	deb@cs.cornell.edu
From: lilleyc@cs.man.ac.uk (Chris Lilley)
Newsgroups: comp.graphics
Subject: FAQ (was: Re: PICT format? HELP!)
Date: 26 Jul 92 23:42:48 GMT
Reply-To: lilleyc@cs.man.ac.uk (Chris Lilley)
Distribution: comp.graphics
Organization: Department of Computer Science, University of Manchester UK

In article <1992Jul25.134041.16587@highlite.uucp> alan@highlite.uucp (Alan
McConnell) writes: 

>	3.(fools rush in . . .)  In my extremely limited experience lurking
>	on comp.graphics I've seen a remarkable number of requests like mine;
>	"how does one read/write format ZYX?"  Should some expert start
>	developing a FAQ with answers to these questions?  I'd be happy to
>	cooperate by e.g. posting what I know/hope-to-learn about PICTS,
>	TIFS, GIFS, etc.

Well, that would be good. However there is a newsgroup
(alt.graphics.pixutils) specifically devoted to discussion of bitmapped
graphics formats and their interconversion and manipulation. Perhaps you
should post your kind offer over there.

There are a number of groups that cover small specialist areas of the
computer graphics field, and perhaps any new FAQ should not duplicate the
coverage of these groups (who may well have their own FAQs). I am thinking
of the scientific visualisation groups too, here. Also the fledgeling
animation group.

Chris
From: cs903070@ariel.yorku.ca (JIMMY BAKLESSIS)
Newsgroups: comp.graphics
Subject: Convert to GIFF
Date: 24 Jul 92 20:02:02 GMT
Organization: York University, Toronto, Canada


 I have a program that generates a bitmap of an image to a file,i.e
 if the image is 64X64 it will save each pixel (4096 in this case)with
 values from 0 to 255 (intensity).
 When I had access to X-Windows I used a program called with the name
 'xloadimage' to view these images. 
 What I would like to know is whether there is a program that displays
 such images on a DOS system or one that converts such a format to GIFF
 so I can use a GIFF viewer to do my job.

 I would appreciate *any* help.

 Thank You in advance.

 -----------------------
 Jim Baklessis
 York University
 Toronto, Ontario Canada.
 cs903070@ariel.yorku.ca
Newsgroups: comp.graphics
From: spencer@cgrg.ohio-state.edu (Stephen Spencer)
Subject: Re: graf-bib-server 
Organization: OSU Advanced Computing Center for the Arts & Design
Date: Mon, 27 Jul 1992 12:16:28 GMT

In article <5470@m1.cs.man.ac.uk> lilleyc@cs.man.ac.uk (Chris Lilley) writes:
>In article <Bs0LIE.Ev3@cs.columbia.edu> olasov@cs.columbia.edu (Benjamin
>Olasov) writes: 
>
>>The old FAQ referenced a very useful graphics bibliography server that
>>lived at graf-bib-server@decwrl.dec.com.  Mail to this address now
>>results in an 'unknown user' message from the mailer daemon.
>
>>Does anyone know what became of the graphics bibliography server?
>
>Last time I looked there, the entries stopped in 1986. That was last year
>sometime. I guess that interest, money and/or personnel dried up...
>
>>Is there another that's active?
>
>Not that I have heard of, but if anyone knows different?
>
>Chris

The SIGGRAPH Online Bibliography Project is a newly-formed group of
volunteers who will be bringing up-to-date and expanding a computer
graphics bibliography list.  I am leading this effort.

We will be making available via FTP (and hopefully other methods) 
a *much* larger set of bibliographic entries for computer graphics.
Preliminary work is being done right now and we should have an announcement
to make sometime in early fall.



-- 
Stephen N. Spencer, Graphics Research Specialist              ,__o      ,__o
spencer@cgrg.ohio-state.edu  (or spencer@siggraph.org)      _-\_<,    _-\_<, 
(614) 292-3416						   (*)/'(*)  (*)/'(*)
Newsgroups: comp.graphics,comp.sources.wanted
From: edwarda@yoyo.cc.monash.edu.au (Edward Au)
Subject: Help on Delaunay Triangulation
Keywords: Delaunay triangulation
Reply-To: edwarda@bruce.cs.monash.edu.au
Organization: Monash General Access UNIX System
Date: Wed, 29 Jul 1992 02:09:34 GMT

Delaunay triangulation is an optimal triangulation of a set of data points.
Does anyone know where I can get algorithms or preferably source code on
this triangulation method?

Please direct responses to edwarda@bruce.cs.monash.edu.au

Thanks in advance

Edward
-----------------------------------------------------------------------------
email: edwarda@yoyo.cc.monash.edu.au | ASK:
Department of Computer Science       | Ask and you will be given;
Monash University                    | Seek and you will find;
Australia                            | Knock and it will be opened to you.
-----------------------------------------------------------------------------
Newsgroups: comp.graphics
From: graeme@labtam.labtam.oz.au (Graeme Gill)
Subject: Re: 24 bit display of 24 bit images in X on DECStation 5000/240
Organization: Labtam Australia Pty. Ltd., Melbourne, Australia
Date: Mon, 27 Jul 1992 04:33:52 GMT
Summary: Try xli instead
Keywords: 24 bit

In article <1992Jul24.155012.12838@ryn.mro4.dec.com>, vesper@2draw.enet.dec.com () writes:
> 
> |>In article <1992Jul22.214630.5024@noose.ecn.purdue.edu>, dmc@ecn.purdue.edu (David M Chelberg) writes:
> |>|>What I am interested in is in
> |>|>displaying 24 bit images on a DECStation 5000/240 running Ultrix 4.2A
> |>|>with their full 24 bits.  I am aware of XV 2.21 and Xloadimage, but
> |>|>they both appear to first convert to 8 bits.
> 
> I just got a copy of XloadImage, and for the 24 bit Utah Raster Toolkit
> run-length-encoded (RLE) images I have, it does indeed convert to
> 8 bits. I have modified the rle.c file to support 24 bit truecolor.
> I will send you a copy now, and send the Xloadimage developers a copy
> once I get back from SIGGRAPH.

	Then you have an old copy of xloadimage. Save yourself some work
and get a copy of xli instead (export.lcs.mit.edu /contrib/xli.*)
I did the original rle.c for xloadimage and converted it to full 24 bit
a long time ago. xli is an enhanced version of xloadimage and includes
a 24 bit JPEG loader as well as numerous bug fixes, speed ups and minor
enhancements. If you are after 24 bit display programs it is probably worth
checking out ImageMagick on export as well.

	Graeme Gill

Newsgroups: comp.graphics,sci.image.processing,comp.ai.neural-nets
From: icfaragh@cayley.waterloo.edu (Chad Faragher)
Subject: ALGORITHM NEEDED:  Palette Selection
Organization: University of Waterloo
Date: Mon, 27 Jul 1992 14:08:02 GMT


The situation:  An image is stored by giving the rgb value for each pixel.
 
The problem:  How to find the best palette of size-n for a particular image
stored (at arbitrary resolution) as above.
 
The solution:  HELP!!!

Does the algorithm exist?  Is it memory intensive?  Can it be solved with 
recursion (ie octree division)?  Can a neural-net be trained to arrive at
a visually pleasing palette given the original image?
 
All input welcome.
 
Chad Faragher -- University of Waterloo
Newsgroups: comp.graphics
From: sbhatia@mary.fordham.edu (SABU)
Subject: PHIGS IMPLEMENTATIONS
Organization: Fordham University
News-Software: VAX/VMS VNEWS 1.41    
Date: Mon, 27 Jul 1992 15:59:00 GMT
X-Posted-From: mary.fordham.edu
X-Posted-Through: sol.ctr.columbia.edu


Hi,

    Could anybody out there tell me if there are any commercially available
implementations of PHIGS that are available on VAX/VMS running DecWindows
DOS/MS-WINDOWS, and the Unix platform. One such implementation I know of
is Figaro. Are there any more avilable out there??????


thanks,
sabu

////////////////////////////////////////////////////////////////////////
/   Internet:  SBHATIA@mary.fordham.edu                                /
/   BITnet:    SBHATIA@FORDMULC                                        /
/                                                                      /
/                                                                      /
////////////////////////////////////////////////////////////////////////
From: johnson@akula.llnl.gov (  Robert Johnson          )
Newsgroups: comp.graphics
Subject: Frame Grabbers
Date: 22 Jul 92 16:34:35 GMT
Reply-To: johnson@akula.llnl.gov (  Robert Johnson          )
Organization: Lawrence Livermore National Laboratory

I am looking for information/recommendations on frame
grabbers for both the Sun SPARCstation (2,10) and the
PC (386,486) platforms.  At this time, I am basically
looking for a low cost method to grab frames of a
broadcast UHF signal.  It would be nice if I could
simply utilize C function calls to aquire frames
into memory as 8 bit intensity images so that I could
then pass them on to other C functions for image processing.
Frame rate is not really a major concern at this time.
Ultimately, it would be nice to have Datacube like
capabilities for real-time hardware image processing, but
current budget limitations dictate a low end solution.
I prefer to use my Sun but I am also interested in info for
the PC.  Please respond by E-mail.  Thanks in advance.

-------------------------------------
Robert K. Johnson
Lawrence Livermore National Lab
Phone: (510) 422-8375
Email: johnson60@llnl.gov
Newsgroups: comp.graphics
From: vesper@2draw.enet.dec.com ()
Subject: Re: 24 bit display of 24 bit images in X on DECStation 5000/240
Keywords: 24 bit
Reply-To: vesper@2draw.enet.dec.com ()
Organization: Digital Equipment Corporation
Date: Fri, 24 Jul 1992 15:50:12 GMT


|>In article <1992Jul22.214630.5024@noose.ecn.purdue.edu>, dmc@ecn.purdue.edu (David M Chelberg) writes:
|>|>What I am interested in is in
|>|>displaying 24 bit images on a DECStation 5000/240 running Ultrix 4.2A
|>|>with their full 24 bits.  I am aware of XV 2.21 and Xloadimage, but
|>|>they both appear to first convert to 8 bits.  I was wondering what
|>|>were the best/fastest public domain programs to display such images,
|>|>and sequences of such images in rapid succession.

I just got a copy of XloadImage, and for the 24 bit Utah Raster Toolkit
run-length-encoded (RLE) images I have, it does indeed convert to
8 bits. I have modified the rle.c file to support 24 bit truecolor.
I will send you a copy now, and send the Xloadimage developers a copy
once I get back from SIGGRAPH.


|>Consider getting the Utah Raster Toolkit (URT).I don't know off-hand the
|>location from which you can FTP this.

I have been told by a usually reliable source that the UTR can be
copied from princeton.edu:/pub/Graphics.

Andy V
Newsgroups: comp.graphics,comp.windows.open-look,comp.windows.x,alt.toolkits.xview