HDTenEightyP/NetNews huggingface dataset:
From: zhu@sgi.com (Benjamin Zhu)
Newsgroups: comp.graphics
Subject: Re: Determining if a polygon is convex
Date: 14 Oct 1992 20:16:12 GMT
Organization: Silicon Graphics, Inc.
NNTP-Posting-Host: graphack.asd.sgi.com

In article <1bhn7mINNbpk@fido.asd.sgi.com> zhu@sgi.com (Benjamin Zhu) writes:
>In article <1bhm1bINNb1m@fido.asd.sgi.com> gavin@krypton.asd.sgi.com (Gavin Bell) writes:
>>>>Does anyone know a nice quick way to determine if a polygon is convex?
>>
>>I think the following will work:
>>
>>Figure out the angles of all of the polygon's corners.
>>
>>If they aren't all the same sign, the polygon is concave.
>>
>>Else figure out the sum of 180 degrees minus each angle.
>>  If the sum is 360 or -360 degrees, the polygon is concave.
>>  Else it self-intersects somewhere.
>>
>>--
>>--gavin     (gavin@sgi.com,  (415)390-1024)
>
>
>	So where do you tell if it's convex?
>
>	I do not read the algorithm very carefully, since in
>	general I am very dubious of any claim that you can
>	determine the convexity of an arbitrary polygon in O(n).
>	I think the lower bound of this decision problem is in
>	fact O(n*ln(n)) based on the decision tree model (as
>	is argued for sorting.)
>

	Actually I was not so sure about my statement that the
	lower bound is O(n*ln(n)) any more.

	In fact, here is the algorithm that might work, and is
	actually O(n). Notice this is sort of similar to Gavin's
	algorithm, except maths has been modified.

	(1) Fred's pass one.

	(2) Determine if the sum of interior angles is (n-2) * \phi
	If so, convex. Otherwise, not.

	Hypothesis:
	If the sum of interior angles is (n-2) * \phi, and each
	interior angle is less then \phi, then the polygon is convex.

	I have not been able to prove or disprove this hypothesis.
	I believe substantial knowledge in topology or projective
	geometry will be needed to either prove it or construct an
	counter example. I wish I had not squandered my maths all
	along:-)
	
	I shall pose it to several maths experts I know and try it
	in sci.math.

	So far, we have at least reduced the algorithm complexity
	to O(n*ln(n)) (my first solution.) If the hypothesis is
	proven, then we have an O(n) algorithm. I hope that will
	happen.

	Ben

--
Benjamin Zhu             ;;; Priest of ucode and self-appointed bug terminator
Silicon Graphics, Inc.   ;;; ``Just call my name, I will be there.''
zhu@graphack.asd.sgi.com ;;; ``Projective geometry is all geometry.'' - Cayley
(415) 390-1187           ;;; ``Learn forever, young forever.'' - Anonymous
Newsgroups: comp.graphics
From: merlyn9@cbnewsd.cb.att.com (michael.t.sedwick)
Subject: Re: WANTED: Utilities for POV ...
Organization: AT&T
Distribution: usa
Date: Mon, 12 Oct 1992 19:27:27 GMT

In article <oetiker.718874462@tardis48> oetiker@iis.ethz.ch (Tobias Oetiker) writes:
>Hi,
>I wounder where I could get all thos utils for pov, promised in
>the documentation ... or are there none ready yet ???
>
>thanks tobi

... I'd check out a few raytracing BBS's FIRST!!!!

Reccomended: (as pointed out in the POV docs)
  You Can Call Me Ray  (in Villa Park, Il.)
  The Graphics Alternative (in So. Calf.)

the numbers are not in my head... both have hi speed connections (9600, 14,400)
BUT the numbers can be found within the fist 10 pages of the POVray docs, as I recall.


			---michael


!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Michael T. Sedwick                              NCR   [[AT&T Computer Systems]]
merlyn9@ihlpl.att.com                           Server Business Unit
Systems Administration;                         Naperville, Il.
Programming; User Pacification                  (708) 979-1026
(it's a h*ll of a job, but some has to do it)
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
From: bh419@cleveland.Freenet.Edu (Ted B Samsel)
Newsgroups: comp.graphics
Subject: TIFF in ARC/INFO Image Integrator
Date: 13 Oct 1992 14:08:33 GMT
Organization: Case Western Reserve University, Cleveland, Ohio (USA)
NNTP-Posting-Host: hela.ins.cwru.edu


  Friday I scanned some aerial photos with MIPS into TIFF format
to import into ARC/INFO's Image Integrator. No problem there, but
the scanned image on the VGA monitor was exceedingly sharp (quite
nice, in fact). But on the Data General workstation, the image is
quite scuzzy and flat looking. I know this is in part to the
GKS kernel, but I would like to know how I should go about punch-
ing up the resolution of the TIFF.
Thanks,
wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww
""   Ted Samsel (TBSAMSEL@QVARSA.ER.USGS.GOV)                                ""
""          or  (TBSAMSEL@DG11SVARMD.ER.USGS.GOV)                            ""
||          or  (BH419@CLEVELAND.FREENET.EDU)                                ||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     "Don't you feel more like you do now than you did before?"
wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww
-- 
Ted....
Newsgroups: comp.graphics
From: IMAGING.CLUB@OFFICE.WANG.COM ("Imaging Club")
Subject: Re: Wang OPEN/image document imaging for AIX starts shipments
Organization: Mail to News Gateway at Wang Labs
Date: 13 Oct 92 11:11:23 EST

Regarding the question just posted by Juhana Kouhia of Tampere as to
why I posted our reply confirming that Wang OPEN/image for AIX is
in fact shipping now:

The comment was posted in response to the totally inaccurate comment
posted by someone else that the product was not shipping.  I'm not
planning to repost that misinformation, but if anyone would like me to
send them that erroneous posting, I'll be glad to do so.  In general,
people should not go around posting totally inaccurate comments about
companies' products without at least trying to do some checking beforehand,
or maybe asking.  As further evidence that it is shipping, the October
issue of Corporate Computing has an article on their benchmark "tests of
imaging engines."  They "tested seven popular products" and found that
Wang's AIX document imaging has the leading price/performance, and
"performed best in our tests" of the non-proprietary systems.  "If you're
looking for screaming performance, a highly scalable system, and a Unix
solution you should definitely investigate this platform."  Wang's PC
document imaging version was "the fastest PC imaging solution we tested."
I'll be happy to air mail a copy of this lengthy article and benchmark
test report to anyone who wants one.  (It's too long to rekey for Emailing.)

If there's any still any doubt about whether OPEN/image AIX document imaging
is shipping now, it can next be seen November 11-13 at the 100 square meter
Wang stand at the UNIX/Open Systems Expo just outside of Stockholm.  (People
in Tampere will be able to see it shortly in Helsinki/Espoo also.)

Maybe we'll just post future release announcements of Wang AIX document
imaging to the IBM Munich AIX newsletter broadcast over these newsgroups!

Michael.Willett@OFFICE.Wang.com
From: akin@sgi.com (Allen Akin)
Newsgroups: comp.graphics
Subject: Re: wierd polygons (was Re: Determining if a polygon is convex)
Date: 15 Oct 92 17:39:44 GMT
Organization: Silicon Graphics, Inc.
NNTP-Posting-Host: tuolumne.asd.sgi.com

In article <19960@ector.cs.purdue.edu> bouma@cs.purdue.EDU (William J. Bouma) writes:
|                                              ...  Does anyone really use
|    (allow) polygons where the edges cross?  For what reason?

Unfortunately, yes.  A great many CAD databases contain polygons with
self-intersections and degenerate geometry.  These arise from
interactive editing.  Some applications developers are unwilling to
"sanitize" the database because a user would see the cleanup as
unsolicited modification of his data.

Allen
Newsgroups: uk.jobs,comp.graphics
From: mikejm@syma.sussex.ac.uk (Michael J McNeill)
Subject: Research post available at University of Sussex
Keywords: reserach,graphics
Organization: University of Sussex
Distribution: uk
Date: Wed, 14 Oct 1992 11:28:22 GMT

Research Officer Post in Computer Graphics

Temporary post of Research Officer up to end of August 1993 with 
an expectation of extension for a further 12 months to work on 
the development of a multi-Transputer based system to generate 
realistic views of the landscape using information contained in a 
large terrain database.  Applicants should be graduates in 
computer science, engineering or mathematics preferably with 
experience of C and Unix.  Salary in the range 12,129 to 17,827 
pa.

Please reply by letter to 

Professor R L Grimsdale
School of Engineering
University of Sussex
Falmer
Brighton, East Sussex
BN1 9QT



-- 
|      Michael D J McNeill     |                                   |
|VLSI & Computer Graphics Group| mikejm@uk.ac.sussex.eaps (JANET)  |
|     University of Sussex     | ...mcsun!ukc!syma!mikejm (UUCP)   |
|Falmer  BRIGHTON  BN1 9QT  UK |                                   |
Newsgroups: comp.graphics
From: vitek@cursci.co.uk (Vitek Tracz)
Organization: Current Science Tel: +44 71 323 0323 Fax: +44 71 580 1938
Reply-To: Vitek Tracz <vitek@cursci.co.uk>
Subject: Looking for high quality mapmaking system
Date: Wed, 7 Oct 1992 22:14:51 +0000


(It's Graham Toal <gtoal@cursci.co.uk> posting this article; I've
put my boss' address in the headers so that he can get the replies
directly.  Apologies for the wide crossposting - it's quite a wide
request.  We checked the comp.infosystems.gis FAQ before posting.)

My boss Vitek Tracz is trying to help his brother, who is a publisher
in Israel, find some system to produce maps for publication.  I believe
he is willing to buy a hardware platform for a suitable system if it
doesn't run on the ubiquitous PCs and Macs, so it's really the software
that's important.

It has to be a system which supports high quality typeset output - I think
the product will be something like an A-Z or a tourist map.  So it's
really a map-drawing cum typesetting system we're looking for, rather
than some more database oriented thing for plotting population densities
etc.  (Those features would be OK and may be used later, but producing
paper is the primary objective)

Also, is there anyone working in this field in Israel who would be
willing to have a chat with Mr Tracz by phone when he returns home
in a day or two?  (I suspect there could be some consultancy work in
the offing...)

Replies by mail please - my boss doesn't read usenet directly.

Many thanks,

Graham Toal pp Vitek Tracz.
Newsgroups: comp.graphics,comp.graphics.visualization,fido7.graphics
From: jk87377@cc.tut.fi (Juhana Kouhia)
Subject: Re: Wang OPEN/image document imaging for AIX starts shipments
Organization: Tampere University of Technology
Date: Fri, 9 Oct 92 08:51:55 GMT



From fellow netter:
======
In article <199210021947.AA27522@tuna.wang.com>
IMAGING.CLUB@OFFICE.WANG.COM ("Imaging Club") writes:
>The Wang Integrated Imaging System (recently ranked as the number one
>document imaging system by Computerworld) has been ported to AIX, with
>equivalent or better functionality, and named OPEN/image for AIX.
>Customer shipments began in September.
     
Should these sort of "Ads" really be posted here, I really read this
for ideas and other peoples views on hardware, to get away from the
Ads, and get honest opinions (all though some are obviously
opinionated towards their own favorite brand).

Vivek
======


After the above notice Wang decided to repost the article??


In article <199210061739.AA03216@tuna.wang.com>
IMAGING.CLUB@OFFICE.WANG.COM ("Imaging Club") writes:
>Regarding that posting about Wang on comp.graphics which you may have
>noticed, we can confirm that we are now in volume shipping of our new
>Wang client-server RS/6000-based document imaging.  Please feel free to
>send in any questions to our worldwide Imaging Club network, and I'll
>broadcast them.
>
[..deleted..]


I agree on that these advertisements should be kept away from the
comp.graphics -- specially those ads. which poster doesn't respect
others opinions.

Reposting the article was unnecessary.


Juhana Kouhia
=============
Vote Clinton for president!
Newsgroups: comp.graphics
From: gfadel@eng.clemson.edu (George Fadel)
Subject: gl.h and device.h 
Reply-To: gfadel@eng.clemson.edu
Organization: College of Engineering, Clemson Univ.
Date: Wed, 7 Oct 1992 18:15:43 GMT


I had a program written in c and running on an SGI computer using gl.h and device.h

I would like to port the program to a sun workstation (sparkstation IPX) and I 
was wondering if there are any equivalent programs for the sun (public domain in
particular).

Thanks
---
From: zhu@sgi.com (Benjamin Zhu)
Newsgroups: comp.graphics
Subject: Re: Determining if a polygon is convex
Date: 15 Oct 92 04:32:20 GMT
Organization: Silicon Graphics, Inc.
NNTP-Posting-Host: graphack.asd.sgi.com

In article <1992Oct15.022624.963@cis.uab.edu> sloan@cis.uab.edu (Kenneth Sloan) writes:
>0)Assume that you have the subroutine:
>
>    RightTurn(A,B,C)
>
>which returns TRUE iff the path A->B->C describes a strict right turn, 
>and returns FALSE if the path A->B->C describes a left turn, or if the
>points are colinear.
>
>1)Assume that your polygon is represented as: P = (P[0], P[1], ..., P[n-1]).
>
>2)Assume that you know that the polygon vertices are given in
>  counter-clockwise order (that is, convex vertices turn to the LEFT.
>  [This assumption will be removed later, if necessary]
>
>3)CONVEX(P) == for(i=0;i<n;i++)
>                if (RightTurn(P[i],P[(i+1)%n],P[(i+2)%n]) return FALSE;
>               for(i=2;i<n;i++)
>                if (RightTurn(P[0],P[(i+1)%n],P[(i+2)%n]) return FALSE; 
>               return TRUE;
>
>Looks O(n) to me.
>
>Proof of correctness is left as an exercise.
> [stuff deleted]

	Sorry, Ken. This algorithm may not work. I believe I have
	found a counter-example. Since the figure is reasonably
	complicated, and I really want to get some kernel stuff
	done before long, I will send you the example during the
	weekend.

	If you have a proof, then either I have overlooked something,
	or the other way around.

	By the way, I still have not found a counter-example to
	my third solution, which ironically also runs at O(n) time.
	
>
>-- 
>Kenneth Sloan                   Computer and Information Sciences
>sloan@cis.uab.edu               University of Alabama at Birmingham
>(205) 934-2213                  115A Campbell Hall, UAB Station 
>(205) 934-5473 FAX              Birmingham, AL 35294-1170


--
Benjamin Zhu             ;;; Priest of ucode and self-appointed bug terminator
Silicon Graphics, Inc.   ;;; ``Just call my name, I will be there.''
zhu@graphack.asd.sgi.com ;;; ``Projective geometry is all geometry.'' - Cayley
(415) 390-1187           ;;; ``Learn forever, young forever.'' - Anonymous
Xref: sparky comp.graphics:10351 rec.arts.animation:4415
From: tlilley@csugrad.cs.vt.edu (Tripp Lilley)
Newsgroups: comp.graphics,rec.arts.animation
Subject: Re: Wow!  Killer Bee
Date: 8 Oct 92 03:28:16 GMT
Organization: Virginia Tech Computer Science Dept, Blacksburg, VA

rdippold@qualcom.qualcomm.com (Ron Dippold) writes:
> It think it might have been done by Angel Studios here in San Diego,
> so I'll call them and ask, but till then does anyone know anything
> about this one?

   If the bit you're talking about started with a tree going through
seasonal changes, then picked up on the bee (lots of pix of the hive, and
bees milling about?) and went into the chase sequence (which included 
initially three bees, who were successively nixed) ... anyway, if this
sounds like the video you describe, it was originally called 'The Nature'
and appeared in the 1991 SIGGraph proceedings (the same year as Grinning
Evil Death) ... and was done by a Japanese firm (whose name escapes me,
and i don't have the video in front of me) .... if not, ignore this post <g>.

- t.
-- 
 USES disclaim;                                                      |^^\/^^| 2
 Tripp Lilley   -- tlilley@csugrad.cs.vt.edu                         | |\/| |
 The MultiMedia Lab of the Colleges of Architecture and Engineering  |_|  |_|
 Virginia Polytechnic Institute and State University         (silly ASCII logo)
From: adaptive@libra.cs.nps.navy.mil (zyda res acct)
Newsgroups: comp.graphics
Subject: Re: Human Head wanted...
Keywords: 3d mesh head human
Date: 14 Oct 92 18:16:10 GMT
Organization: Naval Postgraduate School, Monterey CA


>	Greetings, all!  I'm in desperate need of a 3d mesh of a human head
>(it need not be terribly accurate or very fine mesh) for a project I'm working
>on.  Either a head or a skull would work, so *please* if you have one, send
>it my way!  Much appreciation in advance!
>
	>-Rat	(schilkk@prism.cs.orst.edu)

Ok, I have human heads and an anatomically correct human skull. The
data is a mesh and the demo contains convert utilities to translate
into various other formats, eg. ASCII, Wavefront, IGES, etc. The demo
runs on a SGI IRIS workstation.

In order to get the Cyberware_demo via ftp do the following:

	1) ftp taurus.cs.nps.navy.mil
	2) login as anonymous, guest as the password
	3) cd pub/dabro
	4) binary
	5) get cyberware_demo.tar.Z

Once you get the demo onto your workstation:

	1) uncompress cyberware_demo.tar.Z
	2) tar xvof cyberware_demo.tar


If you have any questions, please let me know.

george dabrowski
dabro@taurus.cs.nps.navy.mil


-- 
george dabrowski
Cyberware Labs

dabro@taurus.cs.nps.navy.mil
Xref: sparky comp.graphics:10433 rec.arts.animation:4453
From: tlilley@csugrad.cs.vt.edu (Tripp Lilley)
Newsgroups: comp.graphics,rec.arts.animation
Subject: Re: Wow! Killer Bee
Date: 9 Oct 92 19:15:20 GMT
Organization: Virginia Tech Computer Science Dept, Blacksburg, VA


  OKay, then it *is* The Nature, they just cut out all of the cool intro and
outro stuff about life in space... I recommend the original (you can almost
hear Walter Kronkite giving you the voice-over at the end "and so we see
that life holds infinite potential, whether on earth, or in space..." <g>)

  well, if you see it in the japanese, you'll know what i mean... <g>

- t.
-- 
 USES disclaim;                                                      |^^\/^^| 2
 Tripp Lilley   -- tlilley@csugrad.cs.vt.edu                         | |\/| |
 The MultiMedia Lab of the Colleges of Architecture and Engineering  |_|  |_|
 Virginia Polytechnic Institute and State University         (silly ASCII logo)
From: hollasch@kpc.com (Steve Hollasch)
Newsgroups: comp.graphics
Subject: Re: Determining if a polygon is convex
Summary: Counter-example
Date: 14 Oct 92 17:40:18 GMT
Organization: Kubota Pacific Computer, Inc.
Originator: hollasch@thorn

fred@kpc.com (Fred Fisher) writes:
> Does anyone know a nice quick way to determine if a polygon is convex?

zhu@sgi.com (Benjamin Zhu) writes:
| 
| (1) Throw away vertex ordering, and compute the convex hull of
|     these vertices. If the computed convex hull is identical to the
|     original polygon, the old polygon is convex. Otherwise, not!

                                                0 _____ 3
                                                  \   /
                                                   \ /
    This fails for a bow-tie polygon, i.e.:         X
                                                   / \
                                                  /   \
                                                2 ~~~~~ 1

______________________________________________________________________________
Steve Hollasch                                   Kubota Pacific Computer, Inc.
hollasch@kpc.com                                 Santa Clara, California
Xref: sparky comp.graphics:10338 comp.graphics.visualization:1464
From: checker@acf5.NYU.EDU (checker)
Newsgroups: comp.graphics,comp.graphics.visualization
Subject: Re: Issues of Computer Graphics
Date: 7 Oct 92 23:13:08 GMT
Followup-To: comp.graphics
Organization: New York University

rsc@altair.csustan.edu (Steve Cunningham) writes:
>Instead, we will "publish" an on-line
>special (unnumbered) issue about that time that will appear on siggraph.org and
>will be available by ftp and e-mail.  This experiment with online publication
>will help fill the publication gap and should help us learn about the viability
>of online publications.

Do you plan on including diagrams and pictures in the issue, or simply
text?  If the former, how?

Chris
From: kluster@gumby.cs.caltech.edu (Kevin Luster)
Newsgroups: comp.graphics
Subject: Re: Req. for refs on reflectance models
Date: 15 Oct 92 20:50:33 GMT
Distribution: usa
Organization: California Institute of Technology, Pasadena
NNTP-Posting-Host: gumby.cs.caltech.edu

jbm@eos.arc.nasa.gov (Jeffrey Mulligan) writes:


>I would appreciate literature references on the subject of computational
>models for color and reflectance.  I am interested in anything
>between Cook & Toorance '81 and the present.  I have one other
>reference on this topic by Borges that appeared in JOSA A in 1991,
>but I suspect that there are things in the computer graphics literature
>that I don't know about.

>thanks in advance,

>Jeff Mulligan
>jbm@vision.arc.nasa.gov
> 

Well, it seems like Roy Hall's book, "Illumination and Color in Computer
Generated Imagery" (Springer-Verlag) is pretty much a standard reference
now. It also contains a list of references at the back which would point
you towards the original sources. If you aren't aware of the Siggraph
Proceedings then you should probably look through them as well.

-K
Newsgroups: comp.graphics.avs
From: tvv@doppler.ncsc.org (Terry Myerson)
Subject: Re: 2D arrows
Organization: North Carolina Supercomputing Center
Date: Wed, 14 Oct 1992 03:00:17 GMT

Hi Folks,

> Hi Ion,
> 
> I think the best thing to do is use a filter which transforms
> a 2D vector field to a 3D vector field.
:
> This filter module is available at the AVS ftp-site (I think).
> If not, I've made one myself (in that case contact me).
> 

The IAC's field_2Dto_3D should do it:

NAME
	Field 2D to 3D - converts a field 2D to a field 3D

SUMMARY
	Name	Field 2D to 3D
	Type	Filter
	Inputs	In 2D Field - 	field 2D REQUIRED

	Outputs	Out Field - 	field 3D

	Parameters
	Name		Type	Default	Choices	NONE

DESCRIPTION
	Field 2D to 3D converts its input field from 2 to 3 dimensions,
	and sets the physical-space dimensions to 3-space.  The data
	remains unchanged.  This module is useful, for example, if you
	have a 3-vector 2D field that you would like to view with Hedgehog,
	which requires field 3D uniform data.

INPUTS
	In 2D Field - field 2D
		The field 2D that needs conversion

OUTPUTS
	Out Field - field 3D
		A field identical to the input field with the array and
		physical dimensionality increased to 3.  The data and
		coordinates remain unchanged.

EXAMPLE NETWORK
	This example reads a field 2D and converts it to a field 3D that
	Hedgehog can use, then displays it.

                        READ FIELD
                             |
                             |
                      FIELD 2D TO 3D
                             |
                             |
                          HEDGEHOG
                             |
                             |
                       RENDER GEOMETRY
                             |
                             |
                       DISPLAY PIXMAP

AUTHOR
	Chris Allen, Unisys Corporation
	Created at U.S. EPA Visualization Center
	National Data Processing Division
	Research Triangle Park, North Carolina
----------------------------------------------------------------
   Steve Thorpe, Application Visualization System Specialist
International AVS Center, North Carolina Supercomputing Center
PO Box 12889   3021 Cornwallis Rd, RTP, NC 27709   avs@ncsc.org
----------------------------------------------------------------
Newsgroups: comp.graphics.avs