HDTenEightyP/NetNews huggingface dataset:
From: woolstar@gumby.cs.caltech.edu (Derek Woolverton)
Newsgroups: comp.graphics
Subject: Re: wierd polygons (and searching for self intersecting faces)
Date: 15 Oct 1992 17:03:53 GMT
Organization: California Institute of Technology, Pasadena
NNTP-Posting-Host: gumby.cs.caltech.edu


	On the subject of bowties, bouma@cs.purdue.edu states:
>> I have written a lot of
>> code to manipulate polygons and have never seen a polygon like this.

> Actually, the bow-tie polygon is not so unusual as it seems. Many people
> who would claim that their data is "bowtie-free" would be surprised. The

    I agree that bowties are fairly rampant once you give the users 
a chance to sweep out a contour.  My first attempt at dealing with these for
my renderer was to generate very fine artifacts.  My new approach is to 
find and destroy bowties (some objects I've encountered have counts > 100).
For a quad, determining the bowtie case is not too painful, but I've just 
about given up on larger cases.
    Does anyone have a good algo for determining if a polygon is self
intersecting (hopefully something O(n) or so)?  If I can filter out these
problem cases, or even better, decompose these into better behaived entities;
the I can sleep soundly at night, relying on dot product tests for convex/
concave determination.

	woolstar@gumby.caltech.edu
	Video Bits
Newsgroups: comp.graphics
From: kincer@hagar.endicott.ibm.com (Mike Kincer)
Subject: GPC PLB's 
Date: Tue, 13 Oct 92 12:50:23 GMT
Reply-To: kincer@owgvm6.vnet.ibm.com
Organization: IBM FSC Owego

Looking for some comparitive data on GPC Picture Level Benchmarks.
I am especially looking for i860 based designs for graphics adapters.


Mike                              __  __o         / "Everythin's IMHO,
Kincer@owgvm6.vnet.ibm.com       __   \<,        /    irrespective of my
~~~~~~~~~~~~~~~~~~~~~~~~~~    ______()/ ()______/      employer's"
Xref: sparky comp.graphics:10683 comp.graphics.visualization:1521
From: g-kwok@cs.yorku.ca (Bernard Kwok)
Newsgroups: comp.graphics,comp.graphics.visualization
Subject: Availability update
Keywords: radiosity, ray tracing
Date: 16 Oct 92 15:39:29 GMT
Article-I.D.: yetti.1499
Followup-To: Radiosity Package Available
Distribution: comp
Organization: York University, Dept. of Comp. Sci. - Toronto

A few weeks ago I posted a public domain radiosity package in comp.graphics and
comp.graphics.visualization. I'm sorry but I neglected to post the address of nexus.yorku.ca
I have also recently learned that it has been mirrored at wuarchive.wustl.edu. and
can be found in: graphics/graphics/radiosity/simple-radiosity

The two network addresses are:

	nexus.yorku.ca           130.63.9.66
	wuarchive.wustl.edu.     128.252.135.4

Sorry for any inconvenience caused.



Bernard Kwok
g-kwok@cs.yorku.ca
Department of Computer Science
York University, Toronto, Canada.

P.S. [I know I shouldn't post personal messages here. But for Randy Hopper at web.b15.ingr.com. 
      Sorry, but I could not seem to be able to mail to your network address.]
From: adaptive@taurus.cs.nps.navy.mil (zyda res acct)
Newsgroups: comp.graphics
Subject: EDGE list from vertices?
Date: 15 Oct 92 05:14:54 GMT
Organization: Naval Postgraduate School, Monterey CA

Does anyone have an algorithm for generating an edge list given a
vertex list?

thanks,

george dabrowski
dabro@taurus.cs.nps.navy.mil
Newsgroups: comp.graphics
From: truscott@gfx.engga.uwo.ca (Ashley Truscott)
Subject:  eps to ps ?
Organization: University of Western Ontario, London
Date: Sat, 17 Oct 1992 01:21:27 GMT

Hi, I have some software that outputs as encapsulated postscript
but my printer only prints out normal postscript.
Does anyone have some software to convert the two.

Thanks

Ash

Newsgroups: comp.graphics
From: dangold1@iastate.edu (Daniel M Goldman)
Subject: A TV as monitor
Organization: Iowa State University, Ames IA
Date: Mon, 12 Oct 1992 16:08:51 GMT

I noticed a unit being sold for $300 that allows you to plug your
laptop into the video port on a regular TV.  Does anyone have any
experience with this? Does it work? Is the image any good?  Does it
have any limitations or assets I'd want to know about?  Please post
or email your comments. Thanks -DmG

Newsgroups: comp.graphics
From: sloan@cis.uab.edu (Kenneth Sloan)
Subject: Re: Determining if a polygon is convex
Organization: CIS, University of Alabama at Birmingham
Date: Thu, 15 Oct 1992 02:26:24 GMT

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.
[HINT: consider using (B-A) x (C-A) to implement RightTurn, and
 think of this as a property of the triangle ABC as well as a property
 of the angle at B.  Now consider the set of triangles examined by the 
 second for-loop.]

Now, returning to assumption 2) - If you don't happen to know which end
is up, modify the above so that the first loop checks to be sure that
all of the vertices turn the same way, and discovers which way that is.
If the answer is "some go one way and some the other", return FALSE.  If
they all go to the LEFT, check for RIGHT turns in the second loop.  If
they all go to the RIGHT, check for LEFT turns in the second loop.

Still O(N).  

Coding and debugging are left as an exercise.

-- 
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
From: spl@ivem.uucp (Steve Lamont)
Newsgroups: comp.graphics
Subject: Re: Hough Transform
Date: 16 Oct 1992 17:36:50 GMT
Organization: University of Calif., San Diego/Microscopy and Imaging Resource
NNTP-Posting-Host: ivem.ucsd.edu

In article <9210151931.AA19662@enet-gw.pa.dec.com> mek@hydrox.enet.dec.com (Mark Klamerus) writes:
>
>	Does anyone have any source for a Hough transform?  I need
>	to put one together for a project and would appreciate a
>	kickstart.

See Pratt, _Digital Image Processing, Second Edition_, pp. 613-622.
It isn't source code but it's a nice, lucid explanation.  The first
edition also covers the subject but in not quite as much detail.  

							spl
-- 
Steve Lamont, SciViGuy -- (619) 534-7968 -- spl@szechuan.ucsd.edu
UCSD Microscopy and Imaging Resource/UCSD Med School/La Jolla, CA 92093-0608
"Twit twit twit/Jug jug jug jug jug jug/So rudely forc'd./Tereu"
                - T. S. Eliot, "The Waste Land," III. The Fire Sermon
Newsgroups: comp.graphics
From: ph+@cs.cmu.edu (Paul Heckbert)
Subject: Re: Fastest way to fill a 2D triangle
Organization: School of Computer Science, Carnegie Mellon
Date: Mon, 12 Oct 1992 19:26:07 GMT

In article <3081@news.cerf.net> jcbhrb@nic.cerf.net (Jacob Hirbawi) writes:
> What I would like to have is the absolutely fastest way to fill a 2D 
> triangle with a solid color.

Jacob, it sounds like you got a good answer or two, but in case you're
still interested in code for this, see the book "Graphics Gems".  I
contributed some very general C code for scan converting convex
polygons to that book.  The code is only negligibly slower than
special-purpose code that is restricted to triangles.  The key on
optimizing such code is the inner loops, and that's going to be the same
whether you're in a triangle-drawing or general polygon-drawing subroutine.

You save a lot of time if you use this scan conversion approach, simply
writing to the frame buffer, versus a seed fill where you draw the perimeter
and then fill in, reading and writing pixels.  The inner loop of the
second would contain about half the frame buffer accesses of the latter.
A further disadvantage of the latter approach is that it fails when the
polygons become thin slivers.

The article:

    %A Paul S. Heckbert
    %T Generic Convex Polygon Scan Conversion and Clipping
    %E Andrew Glassner
    %B Graphics Gems
    %I Academic Press
    %C Boston
    %D 1990
    %P 84-86, 667-680

The code in "Graphics Gems" is available by anonymous ftp from
princeton.edu (128.112.128.1) in the directory pub/Graphics/GraphicsGems.

There's C code in the book for seed fill as well.

-Paul

Paul Heckbert						    ph@cs.cmu.edu
Computer Science Dept., Carnegie Mellon University
5000 Forbes Ave, Pittsburgh PA 15213-3891, USA
From: billabs@nic.cerf.net (Bill Romanowski)
Newsgroups: comp.graphics
Subject: Formula for animation smoothing
Keywords: Animation
Date: 8 Oct 92 18:41:23 GMT
Organization: CERFnet

I'm looking for the function to perform "slow-in and slow-out" for
smoothing movement in animation. Foley's shows an example of this
curve in fig. 21.2 "The graph of a function f(t) with zero derivative
at it's endpoints and constant curve in it's middle section".

The chapter explains the application of this function but not the
f(t) function itself. 

Can someone supply code (for 2D is what I need) or a pointer to info?

bill romanowski
prairie research


Newsgroups: comp.graphics
From: hollasch@kpc.com (Steve Hollasch)
Subject: Re: 3-D objects
Summary: Candidate site
Organization: Kubota Pacific Computer, Inc.
Date: Thu, 8 Oct 1992 18:07:27 GMT

vapspcx@prism.gatech.EDU (S. Keith Graham) writes:
| 
| Steve Hollasch recently posted two lists of 3D objects available
| for anonymous ftp.  One of them was in /pub/DEC/off.tar.Z on
| gatekeeper.dec.com.
| 
| The other (larger) one was on cs.uoregon.edu.  But that machine
| isn't accepting anonymous ftp connections.  (The original post
| of the list was almost a year ago by worley@updike.sri.com)
| 
| Archie doesn't find the object I'm looking for (F15e.iob), so..
| 
| Does anyone have a copy of this archive?  Is it publically available
| anywhere for anonymous ftp or other retrieval?  (And are there any other
| sites with other 3-D object files?)

    Bummer.  I hadn't been to those sites for quite a while, so I didn't
realize they'd expired.  Sorry to mislead you.

    On a slightly more hopeful note, I'm willing to set up a directory on
our machine (ftp.kpc.com) for graphics objects (plus other stuff I've been
thinking about).  The only problem is that the sysadmin who'd help do this
is on vacation (I spoke with him about this before he took off).  If anybody
out there has 3D object data, please send me e-mail to let me know (don't
send the object data just yet).

______________________________________________________________________________
Steve Hollasch                                   Kubota Pacific Computer, Inc.
hollasch@kpc.com                                 Santa Clara, California
From: Ron_Mcnutt@mindlink.bc.ca (Ron Mcnutt)
Newsgroups: comp.graphics
Subject: SVGA PCX Display Problem
Date: 16 Oct 92 05:36:07 GMT
Organization: MIND LINK! - British Columbia, Canada
Distribution: world



Hello...
I am wondering if anyone has had experience with a problem I am having. I
have a 386 DX 33 with a Trident 8900 1MB video card and "Cheer" monitor. I
use 2 programs extensively - PC Paintbrush 4+ and 'ACT3' authoring system.

My problem is in getting SVGA pictures to load into ACT3. They come up fine
in PC Paintbrush (640 X 480 256color) where they have been created, but
simply refuse to load in ACT3. The tech support people at ACT3 (who I might
add have been outstanding and provide excellent support) have no problems
loading these same pictures into a virtually identical computer running the
same Trident video board, etc. and with the same ACT3 drivers.

The screen seems to change to the proper SVGA resolution, but the image will
not load. Other images, EGA etc., load fine with no problems. Simple things
like correct path to image, etc. are not a problem. I am almost ready to give
up and spend the rest of my life in EGA mode. Any suggestions appreciated...
Thanks

Ron McNutt

Newsgroups: comp.graphics
From: steve@aurora.com (Steve Anderson)
Subject: Raster to Vector conversion software...
Organization: The Aurora Group
Date: Wed, 7 Oct 92 23:46:44 GMT


Who are some of the people doing raster->vector conversion software?

(scan an image, output some kind of vector data like AutoCAD, etc.)

I don't care about platforms, formats, etc., I'm looking for general
information.

Pointers to good papers or other references on the topic would also be
appreciated.

Thanks,

--steve



-- 
 H. Stephen Anderson			 | email: steve@aurora.com
 The Aurora Group 			 | Phone: (415) 327-3001
 800 El Camino Real, Suite 200           | "If you are what you eat, then
 Menlo Park, California 94025            |  I'm dead meat..."  -- Timbuk 3
From: dsriniv@uoft02.utoledo.edu
Newsgroups: comp.graphics
Subject: How to get Graphics gems ?
Date: 14 Oct 92 22:04:34 EST
Organization: University of Toledo, Computer Services

Hi 
I am new to this group & just want to know how to get hold of graphics gems in public domain.
Thanx
Vasu
From: spl@pitstop.ucsd.edu (Steve Lamont)
Newsgroups: comp.graphics
Subject: Re: raw RGB bytes from GIF file ??
Date: 8 Oct 1992 14:46:47 GMT
Organization: University of Calif., San Diego/Microscopy and Imaging Resource
Distribution: world
NNTP-Posting-Host: pitstop.ucsd.edu

In article <1992Oct7.211857.96@htsmm1.Las-Vegas.NV.US> mike@htsmm1.Las-Vegas.NV.US (Mike Haaland) writes:
>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. ...

Why bother writing YAFC (Yet Another Format Converter)?  Unless
there's some compelling reason not to, why not just get Jef P's
pbmplus from your favorite FTP site.  It also comes with the X11
distribution, if memory serves.  Use giftoppm and you're in like
Flynn.  There's no ppmtoraw convertor, but the ppm format is dead
simple, an ASCII header and raw bytes in the raw mode, and would take
about five minutes to write, even if you didn't use the library
routines provided.

							spl
-- 
Steve Lamont, SciViGuy -- (619) 534-7968 -- spl@szechuan.ucsd.edu
UCSD Microscopy and Imaging Resource/UCSD Med School/La Jolla, CA 92093-0608
"If you don't think people are this crazy, you need to move to LA!"
                                     - Gary Stollman
From: torbenm@diku.dk (Torben AEgidius Mogensen)
Newsgroups: comp.graphics
Subject: Re: Determining if a polygon is convex
Date: 16 Oct 92 14:13:41 GMT
Organization: Department of Computer Science, U of Copenhagen

wb104@mbuf.bio.cam.ac.uk (Wayne Boucher) writes:

>/*
>The following is hopefully an implementation of the algorithm given by
>Peter Schorn to determine whether a (planar) polygon is convex.  I have
>changed the idea slightly, so beware!  The algorithm checks for those
>points where the x-coordinates and y-coordinates change from increasing
>to decreasing, or vice-versa.  For x (and similary for y) this must occur
>exactly twice (if you think of the array as circular, not linear), and
>the two x changes must alternate with the two y changes (with suitable
>care taken of what is meant by alternation).  Any formal proofs that
>this really works?
>*/

I doubt that it will work. Consider the (rather crude) drawing below,
with vertices marked by A,B,C,D.

	    A
	    |\
	    | \
	   /   \
	  |     B_
	  |       \_
	 /          \_
	D---___	      \_
	       ---___   \_
		     ---__\C

This is clearly not convex, but

	Between A and B, x increases and y decreases.
	Between B and C, x increases and y decreases.
	Between C and D, x decreases and y increases.
	Between D and A, x increases and y increases.

So x changes at C and D, y changes at C and A. Thus they both change
two times, and they are interleaved (if you allow any order on
simultanious changes, which it appears that you do).

	Torben Mogensen (torbenm@diku.dk)
From: andy@osea.demon.co.uk (Andrew Haveland-Robinson)
Newsgroups: comp.graphics
Subject: Newsgroup for POV files??
Date: 13 Oct 92 03:20:36 GMT
Organization: Haveland-Robinson Associates


In article <1992Oct12.163727.14232@arbi.Informatik.Uni-Oldenburg.DE>
Frank.Neumann@arbi.informatik.uni-oldenburg.de writes:

>To get info, [POV mailing list] send a mail containing the body 'help'
>             to  listserv@trearn.bitnet
>To subscribe, send a mail with this body to the same address:
>             subscribe dkb-l <your full name>
>To submit articles, send them directly to dkb-l@trearn.bitnet.
>

Thanks for the info Frank, I'll sign up...

>On another note, I maintain a directory at our ftp site that deals with
>DKB/POV and related stuff. Among them are also some data files for these
>programs. Our address is:
>
>ftp.informatik.uni-oldenburg.de [134.106.1.9], directory /pub/dkbtrace.

I'll pop in and have a look. If I do convert any of the older ones to run,
then I'll resubmit them.  I should think that everyone into dkb will have
upgraded to POV 1.0 by now.

>Of course, this ftp site does not mean I would be against sharing POV
>files in a newsgroup - this way a lot more people might read/contribute,

A newsgroup is a great way to share and disseminate small pov files...
Unfortunately, some of my pov files sometimes run into several tens of meg
in size...

>>I knocked up a simulation of a solar eclipse which I'd like to distribute.
>>Takes a wee while on anything less than a Cray... or nearly a week on a
>>486/33 using the parameters "-w640 -h480 +a0.3 -x"
>
>I'm just checking it out at 160x128, without anti-aliasing..my god, 200
>light sources :-} Do I have your permission to add this scene to our ftp
>archive ?

Certainly, and that goes for anyone else who would like to play with it.
Reducing the number of lights (and adjusting the intensity to match) is
a great way for getting the feel of the "bigness" of the solar system!

By sitting on the "Earth" you can plug in the values and create your own
total and annular eclipses...

I'm thinking about producing shareware 3d truetype fonts for pov, would
anyone actually pay me though?? :-)

I'd like to do more 3d graphics for a living, as the work I do in Desktop
Publishing, illustration and design seems to be drying up...

While I'm at it, is there any further work being done on pov, specifically
optimisation for various platforms, and support for radiosity?

I don't suppose anyone has cracked the problem of tracing a ray back to a
light source via a reflective/refractive surface yet?

Cheers
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    |
+-------------------------------------------------------------------------+
From: vapspcx@prism.gatech.EDU (S. Keith Graham)
Newsgroups: comp.graphics
Subject: 3-D objects
Summary: Copies of the uoregon archive?
Date: 8 Oct 92 16:43:28 GMT
Organization: Free Agent


Steve Hollasch recently posted two lists of 3D objects available
for anonymous ftp.  One of them was in /pub/DEC/off.tar.Z on
gatekeeper.dec.com.

The other (larger) one was on cs.uoregon.edu.  But that machine
isn't accepting anonymous ftp connections.  (The original post
of the list was almost a year ago by worley@updike.sri.com)

Archie doesn't find the object I'm looking for (F15e.iob), so..

Does anyone have a copy of this archive?  Is it publically available
anywhere for anonymous ftp or other retrieval?  (And are there any other
sites with other 3-D object files?)

Keith Graham
vapspcx@cad.gatech.edu
From: rdhunt@sandia.gov (Richard D Hunt)
Newsgroups: comp.graphics
Subject: Looking for PS to RAS filter?
Date: 7 Oct 92 16:47:33 GMT
Organization: Sandia National Laboratories


I'm looking for a program to convert 8 and 24-bit color
postscript images to a raster format, preferably Sun
raster.  If anyone can tell me where I can locate the
source code to a program like this I would appreciate
it.  

Please post any responses or send email to:

      rdhunt@sandia.gov

Thanks,


Richman (Richard Hunt, 9215)
Newsgroups: comp.graphics,alt.graphics
From: cwm@Turing.ORG (Chris W. Morris)
Subject: Re: scanning slides/negatives.
Keywords: slides,negatives,scanner,photostyler
Organization: The Turing Project, Charlottesville Virginia.
Date: Sat, 10 Oct 1992 16:19:24 GMT

Thanks for your interest,
Chris W. Morris
cwm@Turing.org


Newsgroups: comp.graphics
From: djb@geovision.gvc.com (Darren Burns)
Subject: radiosity question
Organization: Not officially GeoVision Systems Inc., Ottawa, Ontario, Canada
Distribution: na
Date: Thu, 15 Oct 1992 17:51:32 GMT

Hi,

I have a question for those who know something about how radiosity is
implemented.

Basically, for doing radiosity, you divide a large polygon into patches.
You calculate the light intensity for each patch individually and then
when it comes time to render the picture, you smooth out the patches
using Gouraud shading or whatever.

Each patch can have a different intensity value.  The problem comes when
there is an object blocking the light from hitting one patch, while
letting light shine on a neighbouring patch.  Let's say you have a very
thin object standing vertically on a desktop.  There's a light on the far
side of it, so the thin object is casting a shadow on the desktop on the
side nearest to us.  Consider a point on the desktop just this side of the
thin object -- it should be in shadow (completely black if there's no
other light sources and no ambient light).  Patches on the closer side are
in fact dark, but patches on the far side of the object are bright.  When
rendering the point in question, the dark patch and the brightly lit patch
are averaged, resulting in a dimly lit section on the desktop near the
base of the object.

Is there a solution to this, other than making the patches really small
(which increases computation time)?

This sort of thing also applies any time you have an object in contact
with another object (eg. a book sitting on a desktop).  You'll get
half-shadows near the book because patches underneath it aren't getting
any light.

Thanks in advance for any help,
Darren Burns