HDTenEightyP/NetNews huggingface dataset:
From: belme@waterloo.hp.com (Frank Belme)
Subject: Ray Tracing in General
Date: Wed, 9 Sep 1992 21:10:12 GMT
Organization: HP Panacom Div Waterloo ON Canada
X-Newsreader: Tin 1.1.3 PL5

I have become very interested in ray tracing lately.  I am an experienced 
programmer and was interested in writing a ray tracer.  I have Roy Hall's book
on illumination models to help me along.  I was wondering if someone could help
me with some simple questions.  The idea of how ray tracing is actually
implemented is new.

I just need a very basic description of a good procedure to follow for
rendering a simple scene once I have the scene defined.  This probably seems
like a silly request but the concept is new to me.

The types of things I need to know are based on the main loop (excluding distributive tracing and all of the specifics).  I need to know how to store the objects for intersection testing (ie. a good type of tree) and the procedure for
testing intersections.  Nothing that is object specific.  I just want a very
basic description.

Thanks.  Frank Belme
From: diskount@micromed.com (don hirschfeld)
Newsgroups: comp.graphics
Subject: Re: 24 bit images
Date: Fri, 11 Sep 92 17:22:31 PDT
Organization: Micro-Medic BBS - +1 408 279 5240 - Public Access

rounsley@jeeves.ucsd.edu (Steve Rounsley) writes:

> Hi ,
> 	I have recently purchased a 24bit video card -(speedstar
> 24x), and was hoping to get some images that can take advantage
> of this.  Does anybody have any suggestions for archives of
> 24bit images.  Also which viewers can handle 24 bit right now?
> Any input would be appreciated....
> 		Steve Rounsley

I know of no DOS viewers that have 24X drivers. Most Windows graphic 
programs which can use 24bit Targa, TIFF, BMP files can be used. Look for 
any .tga files which are 24bit. I have the card and no render to 24bit on 
the PC and Amiga and view it in Windows with Graphic Workshop for Windows 
(shareware).

-- 
diskount@micromed.com (don hirschfeld)
From: oj@miki.pictel.com (Oliver Jones)
Newsgroups: comp.graphics
Subject: SIGGRAPH '92 proceedings CD -- Windows viewer
Summary: where's the latest?
Date: 14 Sep 92 14:39:12 GMT
Reply-To: oj@pictel.com
Followup-To: poster
Organization: PictureTel Corporation

The MS Windows viewer program on the SIGGRAPH '92 Proceedings CD
doesn't work on my Windows 3.1 386 PC (it gets a GP fault).  Has
anyone else had this problem?  Is there a later/better version of the
viewer anyplace on the net?

Reply to me; I'll post a summary.  Thanks.
Ollie Jones
From: ekirby@buckeye.boeing.com (Elizabeth Kirby)
Newsgroups: comp.graphics.explorer
Subject: plot3d module
Date: 10 Sep 92 21:21:30 GMT
Reply-To: ekirby@buckeye.boeing.com (Elizabeth Kirby)


Hi,

	I'm trying to display data using the plot3d module and
am getting no results.   I`ve tried it on the data supplied with
explorer (in the $EXPLORERHOME/data/plot3d directory) as well as 
with my own data.   I'm hooking it into a network which consists
of 

	readplot3d -|      |- generate colormap
                    |      |
	            |      |
		   volume to geom
			|
			|
		     render

	Does anyone know why I'm not getting any picture?

		Thanks,		Beth
From: hashimoto@sgi.com (Roy Hashimoto)
Newsgroups: comp.graphics.explorer
Subject: Re: plot3d module
Date: 11 Sep 92 16:40:42 GMT
Organization: Silicon Graphics, Inc.

In article <82511@bcsaic.boeing.com> ekirby@buckeye.boeing.com (Elizabeth Kirby) writes:
>	I'm trying to display data using the plot3d module and
>am getting no results.   I`ve tried it on the data supplied with
>explorer (in the $EXPLORERHOME/data/plot3d directory) as well as 
>with my own data.   I'm hooking it into a network which consists
>of 
>
> [ basic VolumeToGeom map deleted ]
>
>	Does anyone know why I'm not getting any picture?

The common reason no picture is shown with VolumeToGeom is that alpha
(opacity) values less than 1 are not provided in the colormap.  There
should really be a single large splat representing the whole volume in
this case.

Play with the alpha mapping in GenerateColormap, and something should
show up for you.

Roy Hashimoto
hashimoto@sgi.com
From: hashimoto@sgi.com (Roy Hashimoto)
Newsgroups: comp.graphics.explorer
Subject: Re: IsosurfaceLat2 normals
Date: 11 Sep 92 16:54:36 GMT
Distribution: na
Organization: Silicon Graphics, Inc.

In article <1992Sep10.220413.11698@ncar.ucar.edu> scheitln@ncar.ucar.edu (Tim Scheitlin) writes:
>I have a question about the Explorer IsosufaceLat2 module.
>Some of the polygons in the isosurfaces I am generating with this module 
>appear to have their normals pointing in the wrong direction.

That's rather peculiar, all the normals should be right or all should be
wrong.  What kind of graphics do you have, do you see the same behavior
on the original IsosurfaceLat, and is your input lattice curvilinear?

>My question is:  Is the problem I am having with incorrect normals 
>related to the bug in the original Marching Cubes algorithm?

No, that bug just causes polygons to be missing.  Normal generation is
entirely separate.

Here are my guesses:

1.  You have a curvilinear lattice that reflects on itself so that cells
can have two different "senses".

2.  The module has a bug in normal generation.  Quite possible, but it's
strange that we haven't seen it before.

3.  There is a bug in the rendering code or the GL.  Very unlikely, but
not out of the question.

Roy Hashimoto
hashimoto@sgi.com
From: hashimoto@sgi.com (Roy Hashimoto)
Newsgroups: comp.graphics.explorer
Subject: Re: Problems with snapshot of Render
Date: 15 Sep 92 15:59:43 GMT
Organization: Silicon Graphics, Inc.

In article <92258.132830SONDWIJA@HASARA11.BITNET> SONDWIJA@HASARA11.BITNET writes:
>I am creating animations with Explorer and have some strange problems with
>the Render module. The images that I have generated with the Render module
>are written to disk by hooking up the Snapshot port to the WriteImg module.
>Each time a picture of the animation is produced in the Render window
>I fire the snapshot port and a picture is written to disk. However, not the
>picture that is shown in the Render window is written out but the previous
>picture. The result of all this is that my first picture of the animation is
>rubbish and the last picture is missing. To me this looks like a problem
>with some buffers or so but could somebody help me out ?

We have recently discovered this problem using Starter graphics on an Indigo
in double buffer mode.  The workaround is to use single buffer mode; we are
working on a fix for the next release.

If you are using different graphics, please let us know.

Roy Hashimoto
hashimoto@sgi.com
Newsgroups: comp.graphics.explorer,comp.graphics.visualization,comp.graphics.avs
From: williams@casbah.acns.nwu.edu (Gus Williams)
Subject: Coarse-grained data languages
Organization: Northwestern University, Evanston, Illinois, USA
Date: Mon, 7 Sep 1992 16:43:04 GMT


Some time ago I saw the answer to this question but did not save the
message.  I am now at the stage where it is needed :')

I have heard of the underlying data scheme behind such packages as
AVS and IRIS Explorer as being called "coarse-grained data flow" and
the previous message (mentioned above) had references to a PhD thesis
from MIT (if my memory serves correctly) by an author who went on to
Evans and Sutherland to continue the research.  The message also mentioned
several other references for this subject.

Does anyone know of any references to this data flow scheme?
Am I correct in terming these packages "coarse-grained data flow"?
If not can anyone point me to references that do describe the
underlying structure for these packages?

Any help would be appreciated.

Newsgroups: comp.graphics.explorer,comp.graphics.visualization,comp.graphics.avs
From: eugene@wilbur.nas.nasa.gov (Eugene N. Miya)
Subject: Re: Coarse-grained data languages
Organization: NAS, NASA Ames Research Center, Moffett Field, CA
Date: Wed, 9 Sep 92 17:49:28 GMT

Robbie Babb at the Oregon Grad Inst. is one of the people associated with
coarse grain data flow.  Not specifically for graphics programming.
Robbie is the Editor and Chief of Scientific Programming.  Numerous
non-computer graphics references exist.  You can go back to Jack Dennis (MIT)
for the original concept of data flow.  Everybody else's definition differs
slightly.  Also look up Petri nets.

--eugene miya, NASA Ames Research Center, eugene@orville.nas.nasa.gov
  Acting Associate Editor, Software and Publication Reviews
  Scientific Programming
  {uunet,mailrus,other gateways}!ames!eugene
Ref: Mathematics and Plausible Reasoning, vol. 1, G. Polya
Newsgroups: comp.graphics.explorer
From: gds@casper.cs.uct.ac.za (Riel Smit)
Subject: Datascribe: inputting multiple sets of non-homogeneous data
Reply-To: gds@cs.uct.ac.za
Organization: Computer Science Department, University of Cape Town
Date: Tue, 15 Sep 1992 07:56:02 GMT

How do one do it?  I am new to explorer and can't find the answer either in
the manual or by experimenting (at least not within the time I have
available :-)

Can someone point me in the right direction as to how to read the follwoing
data into one or more latices (the data is in binary form, but that has not
been the problem):

  id1          (char[11] string of ASCII characters identifying data set 1)
  nobs1        (int: number of observations>
  junk         (real[20]: data I don't care about)
  data1        (int[5,nobs]: five data values I'm interested in with 
	                     data[1,i], the x-coordinate;  y-coordinates
                             can be taken to be 1,2,3,4...)
  id2           (data set 2)
  nobs2
  junk2
  data2
  id3
  nobs3
  ...

It was fairly straightforward to create a map that reads the first set of 
data into a lattice, but how do I tell it now to repeat that until it finds
an end of file?  The only way I can see is to define an array, but array
elements cannot be non-homogeneous (used here to indicate "consisting of
different types")

If I could define an array of structs, no problem ... :-)  (Even though the
data file does not say how many data sets there are, I can always find out
off-line).

Do I have to write my own input module rather than use datascribe?
Any help would be much appreciated.
-- 
Riel Smit,  Computer Science                              gds@cs.uct.ac.za
University of Cape Town                      gds%cs.uct.ac.za@rain.psg.com
From: gln@iti.org (Glen Niebur)
Newsgroups: comp.graphics.explorer
Subject: 2d Curvilinear latice
Summary: my lattice isn't rectangular
Keywords: latice shape
Date: 8 Sep 92 17:40:28 GMT
Organization: Mayo Foundation, Rochester MN. Campus

This is probably a beginners question, but i can't seem to find it in TFM.
I have a set of points which represent a bicubic surface.  My problem is
that explorer seems to want a rectangular grid of points, but my surface
doesn't have the same number of control points in each row.  It looks
something like this

       x  x  x  x
    x  x  x  x  x  x
 x  x  x  x  x  x  x  x
 x  x  x  x  x  x  x  x
 x  x  x  x  x  x  x
    x  x  x  x  x
       x  x  x  x

Is there a way to make datascribe read this and display/contour it in
explorer.  Can i create dummy points for the extras, and then have eplorer
ignore them when contouring?

Thanks in advance for any help.

Glen

--
Glen Niebur     | These sobering sights i've seen in the city of angels
Mayo Clinic     | have all been one rude awakening that was due to me
Biomechanics Lab|  ...in heaven
gln@mayo.edu    |            ~Natalie Merchant
Newsgroups: comp.graphics.explorer
From: sean@petvax.mni.mcgill.ca (Sean MARRETT)
Subject: (Q) Plotting contours over high-order finite-elements
Reply-To: sean@petvax.mni.mcgill.ca (Sean MARRETT)
Organization: Positron Imaging Labs, Montreal Neurological Institute
Date: Wed, 16 Sep 92 01:38:59 GMT

As an explorere novice I am interested in finding out if someone can help me withe following problem:

I have a program which produces a solution to a 2-D PDE using high
order (uniform) finite elements. That is to say, the solutions are
computed for the nodes of the elements (triangles) using 2nd-4th order
(alpha)-polynomials. My question is as follows: Is there any easy way to use
the element order when I plot isocontours of the solution, or would
this require writing my own module. Ideally, what I would like to do
is to have a module that would generate contours using the high-order
elements, but it is not clear to me how to go about doing this.

E-mail or post any suggestions. I suspect this has probably ben done,
but I haven't found any references to it yet.
Newsgroups: comp.graphics.explorer
Subject: Problems with snapshot of Render
From: <SONDWIJA@HASARA11.BITNET>
Date: Monday, 14 Sep 1992 13:28:30 CET
Organization: SARA - Stichting Academisch Rekencentrum Amsterdam

Hello,
 
I am creating animations with Explorer and have some strange problems with
the Render module. The images that I have generated with the Render module
are written to disk by hooking up the Snapshot port to the WriteImg module.
Each time a picture of the animation is produced in the Render window
I fire the snapshot port and a picture is written to disk. However, not the
picture that is shown in the Render window is written out but the previous
picture. The result of all this is that my first picture of the animation is
rubbish and the last picture is missing. To me this looks like a problem
with some buffers or so but could somebody help me out ?
 
                                                  Wilfred
From: dpr@ohm.york.ac.uk (David Rossiter)
Newsgroups: comp.graphics.explorer
Subject: Trackerball grey bits
Keywords: sgi render trackerball
Date: 8 Sep 92 14:20:44 GMT
Organization: Electronics Department, University of York, UK

Hi

Does anyone have any suggestions for TOTALLY eliminating the
grey shaded areas that render 'fills in' when drawing the 
trackerball around a data set? I thought I had done it, only
to print the resulting image and find printing 'clouds' where 
near-invisible (and unnoticed) brown pixels had been displayed by
render.

Suggestions much appreciated!

Dave
From: hwa@batman.asd.sgi.com (John Hwa)
Newsgroups: comp.graphics.explorer
Subject: Re: Datascribe: inputting multiple sets of non-homogeneous data
Date: 15 Sep 92 20:36:52 GMT
Organization: Silicon Graphics, Inc.

In article <BuM0pE.LAE@casper.cs.uct.ac.za>, gds@casper.cs.uct.ac.za (Riel Smit) writes:
|> How do one do it?  I am new to explorer and can't find the answer either in
|> the manual or by experimenting (at least not within the time I have
|> available :-)
|> 
|> Can someone point me in the right direction as to how to read the follwoing
|> data into one or more latices (the data is in binary form, but that has not
|> been the problem):
|> 
|>   id1          (char[11] string of ASCII characters identifying data set 1)
|>   nobs1        (int: number of observations>
|>   junk         (real[20]: data I don't care about)
|>   data1        (int[5,nobs]: five data values I'm interested in with 
|> 	                     data[1,i], the x-coordinate;  y-coordinates
|>                              can be taken to be 1,2,3,4...)
|>   id2           (data set 2)
|>   nobs2
|>   junk2
|>   data2
|>   id3
|>   nobs3
|>   ...
|> 
|> It was fairly straightforward to create a map that reads the first set of 
|> data into a lattice, but how do I tell it now to repeat that until it finds
|> an end of file?  The only way I can see is to define an array, but array
|> elements cannot be non-homogeneous (used here to indicate "consisting of
|> different types")
|> 
|> If I could define an array of structs, no problem ... :-)  (Even though the
|> data file does not say how many data sets there are, I can always find out
|> off-line).
|> 
|> Do I have to write my own input module rather than use datascribe?
|> Any help would be much appreciated.
|> -- 
|> Riel Smit,  Computer Science                              gds@cs.uct.ac.za
|> University of Cape Town                      gds%cs.uct.ac.za@rain.psg.com


The dscribe 1.0 cannot handle array of set.  You will need to write
your own input module to handle it in this case.


John P. Hwa
hwa@sgi.com
From: scheitln@ncar.ucar.edu (Tim Scheitlin)
Newsgroups: comp.graphics.explorer
Subject: IsosurfaceLat2 normals
Date: 10 Sep 92 22:04:13 GMT
Reply-To: scheitln@ncar.ucar.edu (Tim Scheitlin)
Distribution: na
Organization: Nat'l Center for Atmospheric Research (NCAR); Boulder, CO

Hi Folks,

I have a question about the Explorer IsosufaceLat2 module.
Some of the polygons in the isosurfaces I am generating with this module 
appear to have their normals pointing in the wrong direction.

This is evidenced by the fact that some of the polygons appear black
while the other polygons in the isosurface are colored correctly.
Flipping the normal produces just the opposite effect.

The man page for this module says that a "KNOWN PROBLEM" is that the
module can produce surfaces with holes because of a bug in the original
Marching Cubes algorithm.

My question is:  Is the problem I am having with incorrect normals 
related to the bug in the original Marching Cubes algorithm?
Is there a fix?

Thanks for any pointers.

Tim Scheitlin
scheitln@ncar.ucar.edu
From: crawfis@ramius.ocf.llnl.gov (Roger Crawfis)
Newsgroups: comp.graphics.explorer
Subject: Only 20 args in mbuilder?
Date: 15 Sep 92 22:42:52 GMT
Reply-To: crawfis@ramius.ocf.llnl.gov (Roger Crawfis)
Organization: Lawrence Livermore National Laboratory

In using mbuilder, the Function Arguments GUI will only let me enter
20 arguments. Is this a hard limit in Explorer? If I try to add an
argument after the last one, it erases the last one and puts in a
blank one.

Any advise?  I have 20 since I was too lazy to try to figure out how
to use nice C and C++ structures with Explorer.

Roger Crawfis
Lawrence Livermore National Lab
(crawfis@llnl.gov)
(510) 423-1320
Newsgroups: comp.graphics.explorer
From: vincent@cadillac.cray.com (Vincent LE BARAZER)
Subject: Explorer versus AVS
Originator: vincent@cadillac
Keywords: AVS comparaison
Organization: Cray Research, Inc.
Date: 14 Sep 92 03:50:10 CDT


 Hi explorers,

 For some commercial reasons, I'd like to know if a report showing
differences between AVS and Explorer exists .
 AVS and Explorer seems to be very close ...and perhaps very different.
I've no experience on AVS .

 If such a report exists, could someone tell where I can copy it from ?

 Many thanx in advance.

 Vincent Le Barazer
 Cray Research France
 Email: vincent@cray.com
Newsgroups: comp.graphics.explorer
From: pascal@nextasy.physics.mcmaster.ca (Pascal Gaudette)
Subject: geom -> tiff/ps
Organization: McMaster University, Hamilton, Ontario, Canada.
Date: Mon, 7 Sep 1992 02:28:13 GMT



Hello.

Does anyone know of a way to convert a file saved from Render
(geom) to tiff or postscript format?

I tried to connect Render to WriteImg, but since my data
is on a 1D lattice, WriteImg doesn't seem to be willing to
cooperate...

Thanks for any help/pointers you may provide.
--
Pascal "The Rascal" Gaudette       pascal@nextasy.physics.mcmaster.ca
MacNUG president                      | *NeXTmail encouraged* 
graduate student, McMaster university | Je ne suis pas infaillible.
Physics and astronomy dep.            | Vive le Quebec LIBRE!
From: lucas@WATSON.IBM.COM ("Bruce Lucas")
Newsgroups: comp.graphics
Subject: 1-, 2-, and 3-point perspective
Date: 6 Sep 92 16:55:37 GMT

1-, 2-, and 3-point perspective are all generated by the same
mapping: (x,y,z) -> (kx/z, ky/z) (where k can be chosen to suit
your purposes and, depending on the exact formulation, may depend
on lens focal length, image resolution, etc.)

Any set of parallel lines in a scene will appear to converge to
a point in the projection onto an image if they are not parallel
to the image plane.  1-point projection arises if there is only one
set of parallel lines in the scene not parallel to the image plane,
as for example in the case of a building seen face-on.  2-point projection
arises if there are two such sets of parallel lines not parallel to
the image plane, as for example in the case of a building seen from
an oblique view but where the viewer (or camera) is not tilted with
respect to the horizontal.  3-point project arises if there are three
such sets of parallel lines not parallel to the image plane, as for
example in the case of a building seen from an oblique view an where
the camera is also tilted with respect to the horizontal.  Thus 1-,
2-, and 3-point projection all arise from the same projection formula
and depend on the relationship of the viewer to the parallel lines
in the scene.

Bruce Lucas
Newsgroups: comp.graphics
From: edwarda@cs.monash.edu.au (Edward Fok Iao Au)
Subject: Re: Digital Image Warping - CODE
Organization: Computer Science, Monash University, Australia
Date: Thu, 10 Sep 1992 06:42:05 GMT

glover@elec.uq.oz.au (Stuart Glover) writes:

>Hi,
>   I have just read George Wolbergs book on Digital Image Warping
>and am interested in implementing some of the code.   In particular
>I would like to use the two pass mesh warp code on pp238 - 240,
>however I can't get it to work properly.  When I pass it through
>with a mesh that maps the input points directly on to the same
>output points, it warps the top part of the image.  It also gives
>lines down the right hand side of the image.  Also if I change the
>mesh, there is no noticeable difference. Has anybody had these
>problems or have I made a mistake in transcribing the code? I fixed
>up some obvious bugs (well i hope they are bugs anyway) but don't 
>know if there are there any more.  Has anyone actually used this
>code and got it working?  If so could they email me with the corrected 
>code or the corrections. Any help would be greatly appreciated.

I have been successful in implementing the two pass mesh warping along
with Fant's 1-D sampling algorithm on a DECstation. The code has been
modified to utilize the Monash Image Library for image i/o. Basically,
the code is the same as in George's book.

The mesh warping code in the book (pp. 222) works perfectly as far as
I have tested it. However, the code for Fant's resampling algorithm
seems to have some minor bug. I don't have my code here so I cannot
locate exactly where the bug is. If I recall it correctly, it seems to
do with the index sampling.

The index sampling part actually computes the inverse mapping between
the source and target images. A full description of the algorithm (with
some examples) by Fant can be found in his paper (see the reference in
the warping book).

I think your problem has something to do with the resampling code, or
the meshes you specified. If one of the meshes is self-intersecting,
the chance is that the resampling algorithm won't work. This is because
the algorithm (George's implementation) caters for mapping within
increasing coordinates. Look at the for/while loop in the beginning of
the code.

If you still have problem, I try to dig out my code.

Edward
______________________________________________________________________________

e-mail: edwarda@bruce.cs.monash.edu.au                           _--_|\
Department of Computer Science                                  /      \
Monash University (Clayton Campus)                              \_.--. /
Australia                                                             V
______________________________________________________________________________
Newsgroups: comp.graphics
From: sz7116084@ntuvax.ntu.ac.sg
Subject: Computer files
Organization: Nanyang Technological University - Singapore
Date: Sat, 5 Sep 1992 03:09:26 GMT

Hello world,
	I am interested in finding a library of good computer graphics files,
especially those animation files of FLI format.Please inform me if there is
such a  library of files. Thanks.

Ong Boon Wee
Nanyang Technological University

>