HDTenEightyP/NetNews huggingface dataset:
From: kluster@gumby.cs.caltech.edu (Kevin Luster)
Newsgroups: comp.graphics
Subject: Re: Problem with zbuffer algorithm and colinear lines...
Date: 15 Oct 1992 16:25:32 GMT
Organization: California Institute of Technology, Pasadena
NNTP-Posting-Host: gumby.cs.caltech.edu

gibsonm@milton.u.washington.edu (Michael Gibson) writes:

>I've been pretty successful implementing a zbuffer algorithm for hidden
>surface removal , except that there are sometimes little lines left over that
>get written on top of everything else. I am fairly certain that these lines
>happen when the three points that make up a face end up being colinear, since
>3 points on the same line don't define a plane so I would guess that my plane
>equation stuff is not valid in these cases. So I was wondering if anybody
>could help me with an easy test to see if three 3-d points lie on the same line
>and therefore aren't valid for plane stuff? I'd sure appreciate any help.

>                                                     Michael

Well, there are two questions here. The first is whether colinear
lines are the source of your Z-buffer problems, the second is how to
detect them if they are.  Since you said you were fairly sure about
the first question I'll only respond to the second:

Question: Given three points A = (Ax, Ay, Az) B = (Bx, By, Bz) and C =
(Cx, Cy, Cz) how do you determine if they are colinear?

Answer: If the vectors defined by taking pairs of these points are
multiples of each other then the points are colinear. So take any two
pairs of these points and construct two vectors, call them S and T:
	S = (Bx - Ax, By - Ay, Bz - Az) (defines vector from B to A)
	T = (Cx - Ax, Cy - Ay, Cz - Az) (defines vector from C to A)

Now if Sx/Tx = Sy/Ty = Sz/Tz then the two vectors are a scaler multiple
of each other and are thus parallel. (Actually if the scaler is negative
then they are anti-parallel, but for this problem that's the same thing.)

Note that you could also find the problem by normalizing S and T and then
taking the dot product and seeing if you get +/- 1. But that would involve
doing a square root which should be avoided if possible.

Now unless if I'm asleep at the wheel that should probably be about the best
way to solve the problem.

-K

Newsgroups: comp.graphics
From: paulf@halcyon.com (Paul Forgey)
Subject: Re: Ray Transformation
Organization: Northwest Nexus Inc. (206) 455-3505
Date: Tue, 13 Oct 1992 07:00:52 GMT

belme@waterloo.hp.com (Frank Belme) writes:

>Hi,

>I was wondering what a good way is to calculate the direction of each ray 
>for ray tracing a scene given an eyepoint, eye direction, and field of view
>angle.  Any help would be appreciated.  Thanks.

A method that I used, which is probably pretty clumsy, but it worked,
was to take point (0, 1, 0), treat it as a 3d stick, and rotate it for
the angles needed.

Basically, I called that point zero rotation, then rotated around Y for
my right/left heading.  Then, I rotated along X for my up/down heading.

I took how many screen pixels of resolution I had for each direction
(this ignores aspect ratios!), divided my field of view angle by that,
and used this constant as my increments.

I would highly recommend using vectors, as I effectively did here, to
move your ray.  Also, I'm working on a method of drawing an imaginary
line to check for intersections, rather than scoot-and-look.

Hope this helps

paulf@halcyon.com

Newsgroups: comp.graphics
From: faraghec@cognos.com (Chad Faragher)
Subject: Re: Nearest point on a line from a point. How do I do it in 3D?
Organization: Cognos Incorporated, Ottawa CANADA
Date: Tue, 13 Oct 1992 14:28:58 GMT

In article <9210101307.AA29403@ucbvax.Berkeley.EDU> S.Marshall@sequent.cc.hull.ac.uk (Simon Marshall) writes:
>
>	Hello to you all, can anyone help?  I'm trying to find the shortest
>    distance from a point to a line, and the coordinates of that point on
>    the line, in 3D.  I've tried to fiddle with the solution for 2D from
>    Graphics Gems II, but without success.  Please can anyone give me a hot
>    tip, or reference where I can find one?
>
>	Specifically, what I am trying to do is work out how high a 1D
>    column is after a sphere of radius r has travelled from (x1,y1,z1) to
>    (x2,y2,z2).  The column is the line (x,y,zlow), (x,y,zhigh).  I need to
>    find the nearest position of the sphere to the column line, so I can
>    work out how much the sphere cuts the column down (if at all).  Any
>    ideas anyone?
>
>	Many thanks, in advance, Simon.
>_______________________________________________________________________________
>Simon Marshall, Dept. of Computer Science, University of Hull, Hull HU6 7RX, UK
>  "Football isn't about life and death.  It's more important than that." Bill
>Email: S.Marshall@Hull.ac.uk    Phone: +44 482 465181    Fax: 466666   Shankley


Xref: sparky comp.graphics:10587 alt.graphics:379 alt.graphics.pixutils:2255
From: spel@hippo.ru.ac.za (Dr. Eberhard W. Lisse)
Newsgroups: comp.graphics,alt.graphics,alt.graphics.pixutils
Subject: dxf to mapinfo
Date: 14 Oct 92 17:57:02 GMT
Article-I.D.: hippo.1992Oct14.175702.17730
Organization: Katatura State Hospital, Windhoek, Namibia

Hi,

I have a DXF file (about 550kb) of a map (of Namibia and its
districts [=counties]) and want to translate this into the
MapInfo format.



It should look something like this:

"district_n",n
x0, y0, x1, y1
x1, y1, x2, y2
.
.
.
x(n-1), y(n-1), x0, y0


In other words n number of lines each defined by its beginning
and ending coordinates.

The districts are unfortunately not marked in the DXF file so
I will have to find the beginning and end of each district
myself, but this is not a problem. 

Any ideas would be greatly appreciated. I do read this group
but email works better.

regards, el

-- 
Dr. Eberhard W. Lisse    \          /                   (spel@hippo.ru.ac.ZA)
Katatura State Hospital   \        |                            (el@lisse.NA)
Dept of Obstetrics & Gyn   \ *    /                         Private Bag 13215
Windhoek, Namibia           ;____/ (postmaster@uonamib.NA) Postmaster NAmibia
From: spl@pitstop.ucsd.edu (Steve Lamont)
Newsgroups: comp.graphics
Subject: Re: Converting RGB -> HSV: How?
Date: 10 Oct 1992 15:06:33 GMT
Organization: University of Calif., San Diego/Microscopy and Imaging Resource
NNTP-Posting-Host: pitstop.ucsd.edu

In article <1992Oct10.012156.56440@qut.edu.au> csn201lawren@qut.edu.au (Steve Lawrence) writes:
>How can I convert a 24-bit RGB encoded colour into HSV encoding?

See pp. 590-592 of Foley, van Dam, Feiner, and Hughes, _Computer
Graphics, Principles and Practice, Second Edition_ (ISBN 0-201-12110-7).
Chapter 17 also covers CMY, YIQ, HLS, CIE, and bunches of other stuff.

							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
From: davis@dssdev.enet.dec.com (Peter Davis)
Newsgroups: comp.graphics
Subject: SIGGRAPH `92 Proceedings?
Date: 9 Oct 92 15:59:04 GMT
Article-I.D.: engage.1992Oct9.150122.18656
Organization: Digital Equipment Corporation


What's going on with the SIGGRAPH `92 Proceedings?  It's been two months since
the conference, and I still have not received this in the mail. Unfortunately,
I was not able to attend this year, but I'm still a member and I expect to get
the Proceedings.  I've already seen these for sale in stores, so why haven't
members gotten them?


                   /
                  /
        /  /  /  /		Peter Davis,	Digital Equipment Corp.
       /  /  /  /				davis@3d.enet.dec.com
      /__/__/__/
     /
  __/
From: fergnani@cadlab.sublink.org (Sandro Fergnani)
Newsgroups: comp.graphics
Subject: .FLI info needed !
Date: 6 Oct 92 16:15:46 GMT
Organization: CAD.LAB S.p.A., Bologna, Italia


Iwolud like to include some .FLI animation in a little program i'm writing.

Does anyone knows if .FLI format is somewhere documented ??
PD or commercial libraries are welcome.

Sandro Fergnani
-- 
Email: fergnani@cadlab.sublink.org                   Phone: ++39 (51) 6130360
CAD.LAB s.p.a., v. Ronzani 7/29, Casalecchio, Italia   Fax: ++39 (51) 6130294
From: hstark@caip.rutgers.edu (howard stark)
Newsgroups: comp.graphics
Subject: LENA picture wanted...
Keywords: lena
Date: 15 Oct 92 19:24:13 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

;


  I looked in all the FAQS I have and could not find an answer
to this question...  
   Where can I ftp the 'lena' image??  I would also like to
know of any sites that contain other DSP related images..
                                       thanx
    hstark@caip.rutgers.edu

------ place witty sig here ------
From: gpr@dcs.exeter.ac.uk (Gordon Price)
Newsgroups: comp.graphics
Subject: Rhubarb
Date: 7 Oct 92 10:31:41 GMT

The following are a few useful tips which you may care to ignore!

1. When printing from MsWindows, (certainly to a dot matrix printer), and I
   imagine, to any other black and white printer, it seems that if you first
   gray-scale your image, better quality is produced - anyone else find this?

2. If you have a diagram you wish to input, (particularly if you wish it to
   end up as line art), I have found that the cheapest and easiest way is to
   trace the image with over head projector pens, onto an acetate, stick this
   to the screen, and copy it!  Rubber band lines tend to be the easiest to
   use for this purpose, and are especially good if they can then be turned
   into bezier curves afterwards - this allows a rough copy to be made and then
   "touched up".

While I'm on the subject, here's a couple of tips which are not graphics
related:

1. OHP pens are also very useful for labeling disks temporarily.  Permenant
   ones are better, since they do not smudge, but you need to use surgical
   spirit to remove it.  (Remember to choose a colour which reflects well for
   the colour of disk you are using)

2. It is often possibly to overcome data errors with disks, by getting the
   disk drive spinning, before closing the door, (though this is more
   difficult these days, since drives tend to cut off automatically - I tend
   to just hold down the "R" key for Retry).  You may shudder at this one, but
   it has saved me on a number of occasions, from losing vital data.


Hope these are of some use.

Gordon Price
(gpr@uk.ac.ex.dcs)
Newsgroups: comp.graphics
Subject: Re: SIGGRAPH `92 Proceedings?
From: rsc@altair.csustan.edu (Steve Cunningham)
Date: Fri, 9 Oct 92 18:25:26 GMT
Organization: California State University, Stanislaus
Summary: They'll be out soon...

In <1992Oct9.150122.18656@engage.pko.dec.com>, davis@dssdev.enet.dec.com
   (Peter Davis) asks:

> What's going on with the SIGGRAPH `92 Proceedings?  It's been two months since
> the conference, and I still have not received this in the mail. Unfortunately,
> I was not able to attend this year, but I'm still a member and I expect to get
> the Proceedings.  I've already seen these for sale in stores, so why haven't
> members gotten them?

These will be mailed out soon.  It always takes us some time to get copies
shipped back from the conference and boxed and prepared for shipment.  This
is not an unusual "delay" -- the conference proceedings always take two to
three months before they are mailed.

As to why these are in stores already, apparently the shipment to Addison-Wesley
didn't come back from the conference but came directly from the printers.

-- Steve Cunningham
Newsgroups: comp.graphics
From: u926135@tasman.cc.utas.edu.au (Adrian Hassall Lewis)
Subject: image enhancement
Summary: image enhancement software info wanted
Keywords: image enhancement
Organization: University of Tasmania, Australia.
Date: Thu, 15 Oct 1992 06:06:23 GMT

I'm looking for advice on image enhancement.  There are three main things I
want to do.

(1)  Scanning in line drawings (using a mac scanner) gives a line which is
actually several pixels wide with a range of greyscales.  When this is 
imported into, say, Macdraw II for manipulation and printing on a laser
printer, the light pixels dropout and a lot of the lines become fragmented
or dropout entirely.
     Is there any way (ie is there any software) that can preprocess a grey-
scale scanned image and turn it into a black&white image?  The software I'm
using at present doesn't appear to be able to do this.

(2)  Can I take a scanned line image and turn it into a postscript file?
(Well actually I suppose I should ask first is this a pointless exercise?,
will this produce a smaller or bigger file?)

(3)  I have a largeish number of GIF files that I'm looking at converting
to JPEG.  The FAQ in this groups says that smoothing the GIF before JPEGing
can help.  However, as I also want to blow up many of the pictures smoothing
will produce unacceptable (to me) blurring.
     NASA, spooks, remote sensers (sp?) commonly do image enhancement (line
enhancement, contrast manipulation, etc), and I have used some primitive image
enhancement software when I did a remote sensing course a while back.  So, I
was wondering if there was any software floating around which would be able 
to get a GIF and do a better job of enhancing it than a simple smoothing?

If you could email me at u926135@minke.iasos.utas.edu.au (please note that
my news computer is NOT my mail computer), I'll post a summary later.

Thanks in advance,
			ajax.

Newsgroups: comp.graphics,rec.arts.animation
From: musashi@blinn.eecs.uic.edu (Miyamoto Musashi)
Subject: Re: Wow!  Killer Bee and re: SIGGRAPH Video Review
Keywords: SIGGRAPH video animation
Organization: Electronic Visualization Lab, U. of Illinois at Chicago
Date: Thu, 8 Oct 1992 01:02:00 GMT

In article <rdippold.718487023@qualcom> rdippold@qualcom.qualcomm.com (Ron Dippold) writes:
> [stuff deleted]
>Anyhoo, there was one sequence in Beyond the Mind's Eye called Killer
>Bee that just blew everyone away.  It consisted of an insect being
>chased by a larger insect.  Anyhow, the animated stuff was of
>excellent quality (especially the spider), but the real killer was the
>background.  Lush vegitation, trees, dead logs, rivers, ponds, etc.,
>looking so damned real, even on extreme closeup, that I actually
>thought that they had superimposed the insects on actual footage for a
>little while.  You could stick this stuff in a Discover channel
> [stuff deleted]

I believe the piece you are referring to was originally titled
"The Nature".  It was produced by Dentsu Inc./Tokyu Agency Inc.
for Osaka's Expo '90 and is indeed a combination of computer animation
and live action.  It was shown as part of the Film & Video show at
SIGGRAPH '90 and is available in its entirety on SIGGRAPH Video
Review No. 66.

In response to Ron Ho's post about how to obtain SIGGRAPH Video
Reviews:

Ordering info:
By phone - within USA  1-800-523-5503
           outside USA 1-708-250-0807
           FAX: 1-708-250-0038

By mail - SIGGRAPH Video Review
          c/o 1st Priority
          PO Box 576
          Itasca, IL  60143-0576
          USA

General info:

An order form and tables of contents for all the SIGGRAPH Video Reviews
are available by anonymous ftp to siggraph.org (128.248.245.250) in the
directory /publications/video_review
This site also contains all sorts of other SIGGRAPH-related goodies.

I believe info is also available by e-mail but I am clueless as
how to access it.  Anybody out there care to comment?  Ralph Orlick?
John Fujii?

        Irv Moy              Internet: musashi@whitted.eecs.uic.edu
        -----------------------------------------------------------
        |        Insert clever comment -> HERE <- and mail        |
        -----------------------------------------------------------
Newsgroups: comp.graphics
Newsgroups: comp.graphics
Subject: Morphing software for an ibmpc compatible
Date: 12 Oct 92  23:47:30 EST

Hi,

maybe this is an faq, but is there any good software voor an ibmpc compatible machine that does a little object morphing ?? or good animation ?

Thanx!

Regards,
 _
|_)
|\_enee.

 * Origin: freusys.nl.mugnet.org, a prive uucp gate at (27:4331/107.19)
Newsgroups: comp.graphics,comp.graphics.visualization,alt.binaries.pictures
From: jpl@tiger.fct.unl.pt (Joao Prospero Luis [ps])
Subject: Re: Q:problem with alt.binaries.pictures 
Organization: Universidade Nova de Lisboa, PORTUGAL
X-Newsreader: TIN [version 1.1 PL6]
Date: Sat, 10 Oct 1992 20:06:31 GMT

Rich Thomson (rthomson@mesa.dsd.es.com) wrote:
: Yes, the problem is that "alt.binaries.pictures" is no longer in
: existence.  It was replaced by the group "alt.binaries.pictures.misc";

	What do you mean "alt.binaries.pictures is no longer in existence"?
	I am reading this in al.binaries.pictures, do you mean that this
does not exist?

		JPL

--
Joao Prospero Luis                 |
Universidade Nova de Lisboa        | Internet: jpl@fct.unl.pt
Faculdade de Ciencias e Tecnologia |
Departamento de Informatica        | Fax:   (+351) (1) 295-5641
2825 Monte Caparica, PORTUGAL      | Phone: (+351) (1) 295-4464
From: kpm8447@tesla.njit.edu
Newsgroups: comp.graphics
Subject: Re: 32k color gifs
Date: 13 Oct 92 12:54:16 GMT
Distribution: comp
Organization: New Jersey Institute of Technology

In article <millernw.718377080@craft.camp.clarkson.edu>, millernw@craft.camp.clarkson.edu (Neal Miller) writes:
> odyy@vax5.cit.cornell.edu writes:
> 
>>Hello, all.  If anybody out there has any 32K color gifs, could you please post
>>it or email it to me?
> 
> 	There are no such things as 32K color gifs.  The very definition of a
> gif image restricts it to 256 colors.  There are other formats that support
> more colors though...  Targa images (*.TGA) come to mind.  I know that my
> raytracer, POVRAY, outputs in targa format by default.

That's not true.  I had a discussion about this last year and someone
said that there is a format for hicolor .gif files but compuserve
won't release it.  I'm sure the same argument was true when people wanted
256 color and not 4 or 16 color .gifs.
(I don't know anything about the format though..sorry)

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Kirk Membry             ( * * * T H I S   S P A C E   F O R   R E N T * * * )

kpm8447@tesla.njit.edu                                    kpm8447@teak.njit.edu
kmembry@andromeda.rutgers.edu                             kpm8447@maple.njit.edu
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Newsgroups: comp.graphics
From: klint@vipunen.hut.fi (Kari E Linden)
Subject: Re: 3-D objects
Organization: Helsinki University of Technology, Finland
Date:  9 Oct 92 15:40:50 GMT

In <70460@hydra.gatech.EDU> vapspcx@prism.gatech.EDU (S. Keith Graham) writes:


>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..
.iob means that this file is in Imagine Object format.

>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?)
There is one archive which has plenty of 3D objects/textures/pictures
made for and done with Imagine raytracing software for Amiga. 

This site has also TTDDDLIB (conversion toolkit) done for Amiga, but
I think that there is source code also, that you propably can translate
it to any other machine.

The site is HUBCAP.CLEMSON.EDU and the files can be explored in 

/PUB/AMIGA/INCOMING/IMAGINE/...

Cheers,
	Kari

-- 
   -------------------------------------------------------------------------
  / Kari Linden        / Helsinki University of Technology                / 
 / kari.linden@hut.fi / Micro Computing Support for Finnish Universities /
-------------------------------------------------------------------------
From: sundar@fiber-one.ai.mit.edu (Sundar Narasimhan)
Newsgroups: comp.graphics
Subject: address of N'th graphics
Date: 13 Oct 92 20:25:54 GMT
Reply-To: sundar@ai.mit.edu
Organization: MIT Artificial Intelligence Laboratory

Hi, Can someone e-mail me the address/phone number for
N'th graphics?
Thanks.
From: goldstei@cgi.com ("Morris Goldstein")
Newsgroups: comp.graphics
Subject: Spyrograph Kinematics
Date: 8 Oct 92 14:07:09 GMT

I recently figured out the kinematics of the popular childrens toy
Spyrograph.  It turns out to be amazingly simple.  With a computer
version, one can create some truely interesting pictures, some not
possible with the mechanical version.

I have two questions:

1.  Is this of sufficient interest that I should post my result to
this or any other appropriate news group?

2.  Are their any journals which might be appropriate to publish an
article on Spyrograph kinematics?


Morris Goldstein (goldstein@cgi.com)
Newsgroups: comp.graphics
Distribution: world
From: vachrisa@deluge.thegrid.com (Alfred F. Vachris)
Organization: The Grid, Westchester, NY USA
Date: Tue, 06 Oct 1992 11:28:14 EST
Subject: Re: octree data wanted

get in touch with RPI. pass requesst to mjohnson.rdrc.rpi.edu
***************************************************************************
 This Message was sent from The Grid, a first-class bbs in lower New York
***************************************************************************
From: checker@acf5.NYU.EDU (checker)
Newsgroups: comp.graphics
Subject: Re: Fastest way to fill a 2D triangle
Date: 8 Oct 92 00:18:51 GMT
Organization: New York University

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. I have two simplistic ways of doing this which
>are not only slow but will not work if some of the pixels within the triangle
>are already set to the color of the boundary. I am sure there are better ways
>of doing this and would really appreciate any pointers.
[examples of fill routines]

Yikes!  If you are the one drawing the triangle in the first place there
is no need to use a fill routine; use a scanline oriented rasterizer. 
Any decent book on graphics will discuss ways of rasterizing triangles
(which are convex polygons).

You should get a tremendous speedup when going from fill to
rasterization.

Chris
From: lees@cps.msu.edu (John Lees)
Newsgroups: comp.graphics
Subject: GPIB color scanner on SPARCstation
Date: 8 Oct 92 14:42:47 GMT
Distribution: na
Organization: Department of Computer Science, Michigan State University
Originator: lees@ahmeek.cps.msu.edu

We have a Sharp JX-300 Color Scanner with a GPIB interface. Currently
it is attached to a Macintosh IIfx. We would like to attach it to one
of our Sun SPARCstations. I would like to hear from anyone who has
done this with the same or a similar scanner:

 1. What GPIB controller do you use in your Sun?

 2. What SunOS software do you use for image acquisition?

 3. How long does it take to scan an image?

Thanks. Please respond by email. I will summarize.
----------                                                     O
 John Lees, Pattern Recognition & Image Processing Laboratory OoO
 Systems Analyst & Lab Manager, Computer Science Department   /O
 A714 Wells Hall, MSU, East Lansing, Michigan, 48824-1027     |
 lees@pixel.cps.msu.edu, lees@msuegr.bitnet, CIS 74106,1324  (|)
   M i c h i g a n   S t a t e   U n i v e r s i t y         _|_