HDTenEightyP/NetNews huggingface dataset:
From: schorn@inf.ethz.ch (Peter Schorn)
Subject: Re: Determining if a polygon is convex
Summary: Yet another O(n) algorithm
Organization: Dept. Informatik, Swiss Federal Institute of Technology (ETH), Zurich, CH
Date: Thu, 15 Oct 1992 22:28:17 GMT

Problem: Given a polygon P with n vertices p(1) to p(n). Determine
in O(n) time whether the polygon is convex. Note: P might be self
intersecting.

Assumptions and definitions:
1) All indices are calculated modulo n.
2) p(1) has the smallest x-coordinate and in case of ties the
   smallest y-coordinate (otherwise a O(n) time cyclic shift is
   necessary).
3) p(m) has the largest x-coordinate and in case of ties the
   largest y-coordinate (m can be found in time O(n)).
4) The predicate rightTurn(p, q, r) is true if and only if
   the point r lies to the right or on the directed line
   segment from p to q.
5) rightTurn(p(1), p(2), p(m)) since the case
   'not rightTurn(p(1), p(2), p(m)' is symmetric.

Idea: A convex polygon consists of a monotone convex upper chain and
      monotone convex lower chain. The following should also work
      for degenerate cases.

Solution:  P is convex if and only if the x-coordinates of
p(1) to p(m) are monotonically increasing and the x-coordinates
of p(m) to p(n+1) are monotonically decreasing and there is a
right turn at each vertex.

P is convex <==> p(i).x <= p(i+1).x for 1 <= i < m  and
                 p(i).x >= p(i+1).x for m <= i <= n and
                 rightTurn(p(i-1), p(i), p(i+1)) for 1 <= i <= n

This can be calculated in time O(n).


Peter Schorn     schorn@inf.ethz.ch
From: gvokalek@augean.eleceng.adelaide.edu.AU (George Vokalek)
Newsgroups: comp.graphics
Subject: Seeking a pc utility to rotate big 2-colour bitmaps
Date: 15 Oct 92 04:58:32 GMT
Organization: Electrical & Electronic Eng., The University of Adelaide


I am looking for a command line utility for the PC which will rotate
bitmaps of A4 pages scanned at 300dpi through 90 degrees (or multiples
thereof).

The bitmaps tend to be about 2500x3000 pixels in size, stored as
BW TIFF files.

I have looked at the PC pbmplus kit, but it will not even run, complaining
about not being in real mode on the 386.  This seems to be the latest 
version of the kit.

Any suggestions appreciated.

George.

--
George Vokalek,                                Dept. of Mechanical Engineering,
                                           University of Adelaide, GPO BOX 498, 
gvokalek@augean.eleceng.ua.oz.au                 Adelaide 5001, South Australia
                                         Phone 61-8-228-4704, Fax 61-8-224-0464
Newsgroups: comp.graphics
From: u882405@franklin.cc.utas.edu.au (Paul J. Watson)
Subject: Practical uses for multi-viewpoint scene analysis  ?
Summary: Request for information about multi-viewpoint scene analysis
Keywords: multi-viewpoint image-analysis scene-analysis
Organization: University of Tasmania, Australia.
Date: Fri, 16 Oct 1992 12:28:53 GMT

Greetings,
          I am looking for information and references which relate to the
practical uses of multi-viewpoint image analysis for object detection, 
as part of an essay which I have to complete for my Honors course.

Some of the possible uses for this method of scene analysis are : 
 o  automated mapping for surveying, from multiple aerial photographs,
      as suggested in a recent issue of National Geographic which described
      the mapping of Mt Everest,
 o  medical image analysis, from CAT/NMR/Sonar/X-ray,
 o  robotic vision, where the images are obtained from multiple TV cameras
      (or other 2D image sensors ??),
 o  3D object encoding for use with 3D morphing, 
 o  Scene reconstruction from moving viewpoint video,

ANY practical (or theoretical) reference/experiences you could provide would be 
*greatly* appreciated. Please e-mail me replies to save bandwidth.

I will post a summary (and the essay itself) if there is enough interest.

Many thanks,

Paul J. Watson.
--
Paul J. Watson - u882405@bruny.cc.utas.edu.au  )  _--_|\   ) Apprentice
                                              (  / oz   \ (   Bitsmith
-- I think therefore I shouldn't be here. -Me  ) \_.--._/  )------------
===President of the Science Honours Club======(======> *  ( 3D photo nut
Newsgroups: comp.graphics
From: andy@osea.demon.co.uk (Andrew Haveland-Robinson)
Subject: Unreal Demo! 
Distribution: world
Organization: Haveland-Robinson Associates
Date: Wed, 14 Oct 1992 00:35:05 +0000


In article <1992Oct13.080024.1@tesla.njit.edu> kpm8447@tesla.njit.edu writes:

>I just got a demo called "unreal" from Ultra Force or one of those
>Sweden, Finland, whoever groups.  This is the most impressive graphics
>demo for a 386 or 486.  My question is, how do they do it?  How do they
>get the routines to redraw so fast?  They animate a world in 3-d and
>fly by really quickly and it works!  Have any of these algorithms been
>implemented into virtual reality or other such 3-d graphics oriented
>programs?  Any info would be appreciated.
> - Thanks

Well?  Where is it then??  :-)

+-------------------------------------------------------------------------+
| Haveland-Robinson Associates     | Email: andy@osea.demon.co.uk         |
| Pine Cottage, Osea Island, Essex |        ahaveland@cix.compulink.co.uk |
| CM9 8UH England.  0621-88756     | Also:  081-800 1708  081-802 4502    |
+-------------------------------------------------------------------------+
Newsgroups: comp.graphics
Subject: Ray/Line interstection in 2D 
From: Hamish_Hubbard@kcbbs.gen.nz (Hamish Hubbard)
Date: 10 Oct 92 13:28:11 GMT
Organization: Kappa Crucis Unix BBS, Auckland, New Zealand

What is the most efficient method of determining the collision point 
of a ray (with just it's angle specified) and a flat-sided object in 
2D. The ray length is determined by the point it's being projected from 
and the point it finally hits. The ray is guaranteed to hit the side 
of an object.

--
Hamish_Hubbard@kcbbs.gen.nz             Auckland, New Zealand
From: slqy8@cc.usu.edu (The Blizzard)
Newsgroups: comp.graphics
Subject: Looking for screen capture utility!!
Date: 15 Oct 92 14:33:51 MDT
Organization: Utah State University

Hi all,
	I sure hope that someone out there can help me out on this one...
What I am looking for is a good (read: high resolution, or as high as I can
get) screen capture utility for MS DOS.  I need this as soon as possible,
and welcome any and all suggestions on the subject.  If I can get one via
FTP, it would be especially appreciated.  (The utility needs to capture a
graphics screen and save it to a file that can be read by another program-
(i.e.  TIFF, PCX, etc.)
Thanks!!  Rick
-- 
-----------------------------------------------------------------------------
Rick C. Larkin              *    "Did I do that?....  I didn't know that THAT
"The Blizzard"              *        would happen!..."  - (User of our net)
Systems Analyst/Programmer  *
Internet:  SLQY8@CC.USU.EDU *
Bitnet:    SLQY8@USU.BITNET *
=============================================================================
Newsgroups: comp.graphics
From: hollasch@kpc.com (Steve Hollasch)
Subject: Re: Determining if a polygon is convex
Summary: Counter-example to adjacent edge cross-product test
Organization: Kubota Pacific Computer, Inc.
Date: Thu, 15 Oct 1992 00:19:16 GMT

pff@pablo.b11.ingr.com (Pablo Fernicola) writes:
| Walk through all the vertices, taking the cross product between 
| the vectors that form the two adjacent edges.  If at any time the 
| normal (resulting from the cross product) "flips", pointing in the 
| opposite direction of the previous normal, the polygon is not convex.  
| As an added bonus, you can use the normal for your face culling too.

    This method only works if the polygon does not      3 ________ 2
self intersect.  Consider again the example on the        \       |
right.  In a right-handed coordinate system, the           \   5  |
cross-product of adjacent edges will always yield           \ /|  |
a normal vector that points towards you; the normal          X |  |
vector never flips.                                         / \|  |
                                                           /   4  |
                                                          /       |
                                                        0 ~~~~~~~~ 1

______________________________________________________________________________
Steve Hollasch                                   Kubota Pacific Computer, Inc.
hollasch@kpc.com                                 Santa Clara, California
From: bstango@ernie.Princeton.EDU (Robert T. Stango)
Newsgroups: comp.graphics
Subject: Looking for Printshop graphics (IBM)
Date: 9 Oct 92 01:41:49 GMT
Article-I.D.: Princeto.1992Oct9.014149.15027
Organization: Princeton University
Originator: news@nimaster


I am not sure if this is the place for this. Please redirect me if there
is a better newsgroup to post to.
I am looking for more graphics for the New PrintShop for the IBM (and
clones). The ones that come with the program are ok, but I would like to
get more for a wider range of card and poster making. If anybody knows
of maybe a server someplace I would be truly greatful. Thanks.

Bob
========================---------------------===========================

Bob Stango                       Internet :bstango@phoenix.Princeton.EDU
Princeton University CIT         Bitnet   :bstango@pucc.Princeton.EDU

****************** MY THOUGHTS AND OPINIONS ARE MY OWN *****************
Newsgroups: comp.graphics
Subject: Re: Converting epsf to tiff or gif
From: marcello@deis20.cineca.it (Marcello Dalpasso)
Date: 8 Oct 92 17:54:52 +0100
Distribution: world
Organization: Dept. of Electronics, Computer Science & Systems, Univ. of Bologna, Italy
Keywords: epsf, gif, tiff

>> You can do it with the wonderful xv package (running in the XWindows environment)
>> developed by John Bradley.
>>
>Humm ... epsf to tiff or gif. I didn't think that it was possible :)
>As a matter of fact xv CAN convert images to PostScript but not the opposite !
>
>The only way I know how to "convert" epsf to any other format is
>to display it and then grab the window and save it GIF or whatever ...


Sorry, I forgot a step!!!
We actually use ghostscript (by GNU) to convert ps (or eps) to ppm, than xv to
convert ppm to (almost) anything!!!

Sorry again.

-- 
	Marcello Dalpasso (e-mail: marcello@deis16.cineca.it)
	D.E.I.S. - Department of Electronics, Computer Science and Systems
	Viale Risorgimento 2, I-40136 Bologna, Italy			
	Phone: +39-51-644-3015 (fax: +39-51-644-3073)
Xref: sparky comp.graphics:10455 comp.os.ms-windows.advocacy:2409 comp.os.os2.advocacy:7321 comp.sys.sgi:14910
From: hunter@phoenix.apana.org.au (James Gardiner)
Newsgroups: comp.graphics,comp.os.ms-windows.advocacy,comp.os.os2.advocacy,comp.sys.sgi
Subject: Re: Considering getting an SGI machine...
Keywords: SGI
Date: 9 Oct 92 15:27:07 GMT
Organization: Phoenix ComSystem
NNTP-Posting-Host: localhost.apana.org.au

dic5340@hertz.njit.edu (David Charlap) writes:

>In article <1992Oct2.141914.8147@njitgw.njit.edu> dic5340@hertz.njit.edu (David Charlap) writes:
>>SGI has anounced NT for one new model workstation.  It is MIPS R4000
>>based, though, so it's likely that NT will be ported to SGI's other
>>workstations if this one works out well.

>One minor correction:  Apparantly (according to one of Brian's posts)
>SGI has demoed a beta of NT on Indigoes.

The new R4000 based pizza box type indigo system that NT will be on
is suppose to be quite price competetive. I'd support the SGI because
you buying a piece of REAL hardware.  It can also run IRIX(unix) if you grow
out of NT. (you could boot up in either OS).
Also an R4000PC (Pc version chip. no secondary cache) still wips
a 486/50 by many times.


James
From: "peter shirley" <shirley@death.cs.indiana.edu>
Subject: Re: Nearest point on a line from a point. How do I do it in 3D?
Organization: Computer Science, Indiana University
Date: Sat, 10 Oct 1992 08:36:41 -0500

One way to get the answer is to represent the line parametrically
and then minimize disytance while varying the parameter.  If your
line goes through (x0, y0, z0) and (x1, y1, z1) and your point
is (xp, yp, zp), then the line is:

	p = p0 + u(p1 - p0)

or

	x = x0 + u(x1 - x0)
	y = y0 + u(y1 - y0)
	z = z0 + u(z1 - z0)

Distance squared from the point to the point on the line is:

	D2 = (x - xp)^2 + (y - yp)^2 + (z - zp)^2

Differentiate D2 with respect to u and set to zero.  This gives
you a linear equation in u which you can solve.

pete

Newsgroups: comp.graphics
From: andy@osea.demon.co.uk (Andrew Haveland-Robinson)
Subject: Human Head wanted... 
Distribution: world
Organization: Haveland-Robinson Associates
Date: Wed, 14 Oct 1992 00:35:05 +0000


In article <1992Oct13.043047.7006@CS.ORST.EDU> schilkk@prism.CS.ORST.EDU writes:

>        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!

I'd like one too, pref in dxf/3ds format...

oh, and on a plate please! :-)

+-------------------------------------------------------------------------+
| Haveland-Robinson Associates     | Email: andy@osea.demon.co.uk         |
| Pine Cottage, Osea Island, Essex |        ahaveland@cix.compulink.co.uk |
| CM9 8UH England.  0621-88756     | Also:  081-800 1708  081-802 4502    |
+-------------------------------------------------------------------------+
Newsgroups: comp.graphics
From: rlg@IDA.ORG (Randy garrett)
Subject: Seeking ADRG viewer under X11
Organization: IDA, Alexandria, VA
X-Newsreader: Tin 1.1 PL4
Date: Sat, 17 Oct 92 01:22:53 GMT


Does anyone have a good recommendation for an ADRG viewer
that runs under X11 or Sun's OpenWindows?  I have seen some
that run on PC's, but haven't been able to find anything
for X.

Thanks,

=================================================================
Dr. Randy Garrett
Computer and Software Engineering Division
Institute for Defense Analyses
1801 N. Beauregard St.
Alexandria, VA 22311
(703)845-6688
FAX: (703)845-6788
rlg@ida.org
          "Picture a witty saying of your choice here."
=================================================================

Newsgroups: comp.graphics
From: andy@osea.demon.co.uk (Andrew Haveland-Robinson)
Subject: Unreal Demo! 
Distribution: world
Organization: Haveland-Robinson Associates
Date: Thu, 15 Oct 1992 00:18:58 +0000


In article <jensenjp.719066201@craft.camp.clarkson.edu> jensenjp@craft.camp.clarkson.edu writes:

>>Well?  Where is it then??  :-)
>
>I have FTP'ed it from ftp.ulowell.edu
>btw get all of the demos in the EuroDemos they are all very impressive
>and most of them have excellent sound for the Blaster/Blaster Pro/and others
>jon

Thanks Jon, will do...

Andy.

+-------------------------------------------------------------------------+
| Haveland-Robinson Associates     | Email: andy@osea.demon.co.uk         |
| Pine Cottage, Osea Island, Essex |        ahaveland@cix.compulink.co.uk |
| CM9 8UH England.  0621-88756     | Also:  081-800 1708  081-802 4502    |
+-------------------------------------------------------------------------+
Newsgroups: comp.graphics
From: douglas@cs.scarolina.edu (David Douglas)
Subject: Re: Klingon and 3d objects ftp
Organization: USC  Department of Computer Science
Date:  8 Oct 92 04:09:40 GMT

g.coulter@daresbury.ac.uk (G. Coulter) writes:

>What is the difference between object files ending in
>.geom and files that end in .geomZU is the second one
>compressed in some way and if so how is it compressed
>and what do you use to de-compres it.


>      \    __
>   AMIGA  ///  Gary Coulter
>     __ \///   SERC Daresbury Laboratory
>     \\\/X/(*)
>      \X//\/   G.Coulter@Daresbury.ac.uk

Well, I can't say this is an absolute solution for your question, but
the "ZU" part of the filename reminds me somewhat of a file-naming
convention I've seen used for compressed, then uuencoded files.  For
instance, a file named  datalist  , after being compressed, usually
has the name  datalist.Z  .  After uuencoding this compressed file,
something like "U" or "UUE" is sometimes added to the end of the
filename, producing  datalist.Z.UUE  ,  datalist.Z.U  , or
datalist.ZU  , etc.  So you might try the following:

uudecode datalist.geomZU

Assuming that this produces the file named  datalist.geom.Z  , you
could then enter

uncompress datalist.geom.Z

thus producing the original file you wanted to use.

By the way, datalist.geomZU would still be around -- uudecoding it
doesn't mean it gets deleted.

(Creating the compressed/uuencoded file could have been done as follows:

compress datalist.geom

uuencode datalist.geom.Z < datalist.geom.Z > datalist.geomZU

)

For a quick check, try editing or viewing the original file,
filename.geomZU -- if you see something like

begin 644 filename.geom.Z

then what I wrote above might work.  Hope this helps!


David Douglas
douglas@usceast.cs.scarolina.edu

Newsgroups: comp.graphics
From: ng@ee.tamu.edu (Kit-Tong Ng)
Subject: gifs file format ? help!
Keywords: file format gifs 
Organization: Texas A&M University
Distribution: comp.graphics
Date: Thu, 8 Oct 1992 04:15:56 GMT

Howdy:

Anyone out there know of where can I get information on GIFs
file fomart ?
I am interested to know in detail how GIFs file are read/stored.
I am trying to display/save gifs images on a SUN workstation.
Any suggestions ( books/ftp.sites/documentations ) are welcome.
I had looked at source codes fo xloadimage, but it is far too, too 
flexible( ie complex ) for my needs.  

Please Email me at : kit@Napolean.tamu.edu

Thanks.
Gig'm, Aggies!
From: gavin@krypton.asd.sgi.com (Gavin Bell)
Newsgroups: comp.graphics
Subject: Re: Determining if a polygon is convex
Date: 14 Oct 92 17:39:55 GMT
Organization: Silicon Graphics, Inc.  Mountain View, CA
NNTP-Posting-Host: krypton.asd.sgi.com

>>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)
Newsgroups: comp.graphics
From: hollasch@kpc.com (Steve Hollasch)
Subject: Re: Determining if a polygon is convex
Summary: He runs up the midfield, he shoots, HE SCORES!!!
Organization: Kubota Pacific Computer, Inc.
Date: Fri, 16 Oct 1992 06:19:41 GMT

schorn@inf.ethz.ch (Peter Schorn) writes:
| ...
| Solution:  P is convex if and only if the x-coordinates of
| p(1) to p(m) are monotonically increasing and the x-coordinates
| of p(m) to p(n+1) are monotonically decreasing and there is a
| right turn at each vertex.
| ...

    I have to second Benjamin's applause; I think you've done it.  I hope to
work on this and hack up some pseudo-code to do this well, but it feels very
good to me.  Not only O(n), but mathematically simple, too.  Way to go!

    I think, though, that you don't need to worry about ties in X
coordinates, you should be able to pick any starting vertex that has the
minimum X coordinate, and assign m to any vertex that has the maximum X
coordinate value.

______________________________________________________________________________
Steve Hollasch                                   Kubota Pacific Computer, Inc.
hollasch@kpc.com                                 Santa Clara, California
Newsgroups: comp.graphics,alt.graphics.pixutils,comp.sys.mac.programmer
From: farm@gpu.utcs.utoronto.ca (B. Munroe)
Subject: Lens flare algorithm/code?
Organization: UTCS Public Access
Date: Fri, 9 Oct 1992 13:07:06 GMT

Does anyone have an algorithm/sample code for a lens flare filter (similar
to that found in Photoshop)?  If you haven't seen the Photoshop filter,
take a look at either the CBS or ABC IDs that are currently on air.  The
lens flare effect is a simulation of what happens to a camera lens when
it is hit by a bright flash of light.  The Photoshop implementation is
nice but buggy.  I'd like to write my own (so I can batch process) but I 
haven't seen any code that describes the process.

Thanks in advance.

Bob Munroe
farm@utcs.utoronto.ca


-- 
.............................................................
Bob Munroe		: Internet>	farm@utcs.utoronto.ca
The Farm		: CompuServe>	71160,3455
From: dbassett@bonnie.ics.uci.edu (Douglas Scott Bassett)
Subject: Looking for two SIGGRAPH articles
Newsgroups: comp.graphics
Reply-To: dbassett@ics.uci.edu (Douglas Scott Bassett)
Organization: Univ. of Calif., Irvine, Info. & Computer Sci. Dept.
Date: 9 Oct 92 19:10:00 GMT

I am looking for two article references mentioned in Computer Principles
and Practice by Foley et. al.  They are...

Donato, N., and R. Rocchetti, "Techniques for Maniuplating Arbitrary
 Regions"  Course Notes 11 for SIGGRAPH 88, Atlanta, GA, August, 1988

Steinhart, J.  "Introduction to Window Management", Course Notes 11
 for SIGGRAPH 89, Boston, MA, August, 1989

Does anyone know where I can find these (or similar) articles?
Course Notes 11 sounds like something the authors created for
themselves (class notes). Is this a publication? If not, then were
these articles ever released in the SIGGRAPH journals?  Thanks,  Doug
From: mike@htsmm1.Las-Vegas.NV.US (Mike Haaland)
Newsgroups: comp.graphics
Subject: Re: raw RGB bytes from GIF file ??
Date: 7 Oct 92 21:18:57 PDT
Distribution: world
Summary: Easy to do
Organization: HyperTech Software

govind@point.cs.uwm.edu (Govind Seshadri) asks:

>Is there some source out there that will generate raw RGB bytes 
>from an input GIF source file ?
>I would be happy to receive any suggestions/pointers towards this.

If you have any GIF decoder code around, a convertor would be easy to
hack together.  The bytes in the raster data are a CLUT (Color lookup
Table), so the byte tells which RGB triplet to output from the colortable
associated with the image.  I assume your working in C.  If so there are
many GIF decoding/viewing routines floating around the NET.


--
Mike Haaland

CompuServe : 72300,1433
Delphi     : MikeHaaland
Internet   : mike@htsmm1.las-vegas.nv.us
Usenet     : ...!htsmm1.las-vegas.nv.us!mike      	
--
Newsgroups: comp.graphics.explorer
From: foulser@homebrew.asd.sgi.com (David Foulser)
Subject: Re: Q:  3D Perimeter --> 3D Uniform Lattice Conversion?
Keywords: lattice perimeter uniform conversion how-to
Reply-To: foulser@homebrew.asd.sgi.com (David Foulser)
Cc: danw@uh.msc.edu
Organization: sgi
Date: Thu, 15 Oct 1992 01:51:55 GMT

Dan,

You should try using the Interpolate module, where you enter perimeter data 
as the source and a lattice of uniform coordinates in the correct coord
space as the set of interpolation points. This will do the interp for you
and be reasonably fast. I'll leave it to you to create the uniform lattice
of coords, though it would be easy in LatFunction(2).

Dave

-- 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
David Foulser					foulser@sgi.com 
MS 1L-545
Silicon Graphics, Inc   			415/390-5338 
2011 N. Shoreline Blvd. 			415/390-6056 FAX
Mountain View, CA 94039-7311 			
Newsgroups: comp.graphics.explorer