Up: graphics resources
One of the most important steps in a visualization project is to
choose the right kind of software for the task. There are several
distinct genres of image generating software, each with its own
strengths and weaknesses.
2D Structured Graphics
Structured graphics programs keep track of the objects drawn, so that they
can be moved and edited later. Typically, a structured graphics program
will enable you to draw lines, polygons, ellipses, place text and so
on. They do not allow you to "air brush" over the whole scene, since
this process is a "pixel" operation, where the color of individual
pixels changes in many objects. Conequently, structured graphics tend to
be better suited to illustrations and diagram s, as opposed to more
"artistic" or photorealistic images. Another useful feature of
structured graphics is that sizes and colors
tend to be independent of the underlying hardware.
- Adobe Illustrator -- Illustrator is a powerful,
high end package. It runs only on the NeXTs at the Center; find it in
/LocalApps directory. Illustrator also interfaces
well with Adobe Photoshop, which is a pixel based, "raster" drawing
program, so between the two, it is possible to produce very high
quality graphics. To learn about Illustrator, consult the manuals in
the Center library.
- xfig --
xfig is a relatively
straight forward, bare bones drawing program. It allows only 8 colors,
but it outputs PostScript directly, integrates very well with TeX, and it is
widely available. This is a good choice for a simple diagram from a
mathematical paper in TeX. The man
page contains detailed information.
- gnuplot --
gnuplot is a
graphing program. That is all it does, but it does that relatively
well. It can make 2D and 3D plots, either from data files, or
constructed out of elementary functions. There are lots of style
options. For more information, consult its
page, or the online documentation, which is probably more useful.
Raster graphics programs are "paint programs". You cannot go back and
select an object and edit it; instead, you change the colors of the
pixels on the screen as you go, and the computer only keeps track of
the image. Thus, one can "air brush" and apply "effects" in a way one
cannot in a vector graphics drawing program. This allows the user to
create beautiful and highly refined images, but like a painting, they
cannot be easily "edited" later. Thus, raster graphics are best for
things like logos and cover artwork -- high quality, but one time
graphics. Another thing to watch out for with raster graphics is that
they tend to depend on the underlying hardware; colors and sizes will
vary from machine to machine.
- Adobe Photoshop -- Photoshop is essentially
the only raster graphics editor the Center has, and there is only one
copy. Ask the staff on which Mac it is currently residing. Photoshop
is the graphic arts industry standard, and is a very powerful program.
Among other things, it works very well for "touching up" illustrations
created with Adobe Illustrator. For more information, consult the
manuals in the Center library.
- IconBuilder -- A quicker, simpler graphics editor
is the Next IconBuilder.app in
provide roughly "MacPaint" level editing. It only works with .tiff
A large proportion of people at the Geometry Center will naturally be
concerned with making pictures of objects with mathematical
descriptions. This enterprise takes place at two levels. On the one
hand, there are occasions when the main objective is simply getting
some picture to look at, in order to better understand an
object. On the other hand, people also need to produce high quality
images to communicate a visual concept.
Typically, one will use specialized mathematical software to produce some
graphical representation of an object. Then, if a high quality image is
desired, the user will use the graphical description of the object
produced in the first phase as input to a 3D modelling and rendering
program where lighting, texture mapping, shadows and so forth can be
added. For example, one might use Mathematica to compute the vertices
of a dodecahedron, and then use Geomview to find a good viewpoint and
add lights and shading. If necessary, one could then use Geomview to
write a Renderman file, which could then be used to render the
dodecahedron in mahogany, through a haze.
There are many ways of producing a first pass graphical representation
of a mathematical object. However, four packages have proved
particularly useful in the recent experience at the Center.
Basic instructions for making mathematical illustrations with them are
3D Modeling and Rendering
The generation of high quality 3D images is complicated and labor
intensive. In terms of ease of use, Geomview is the clear pick for
generating a 3D scene, however Geomview doesn't support texture
mapping yet, or a variety of other high end features. However,
Geomview can output a scene description in Renderman (.rib) format.
By editing the RIB file, one can add texture mapping and so on. Most
frames from the Geometry Center videos "Not Knot" and "Outside In"
were produced with Renderman. Renderman does not do ray tracing
however, so if things like reflections and shadows are important, one
must use something like Rayshade or Softimage. Softimage is
state-of-the-art, boasting the
production credits for Jurassic Park among other things. However, the
learning curve for Softimage is immense, so the need for ray tracing
should be compelling before undertaking a Softimage project.
Similarly, using Rayshade requires learning another scene description
language, not to mention producing the actual description.
- Geomview -- Geomview is the correct choice for
most mathematical 3D modeling. Scenes are described by
(Object Oriented Graphics Language) which one can create
directly, or via the applications noted above. One of Geomview's most
outstanding features is the ability to manipulate a scene in real
time, and interactively set many rendering attributes. This gives the
user the ability to experiment with a scene to find the combination of
rendering options and viewing parameters that most effectively conveys
a visual concept. Moreover, Geomview can output a scene description
in RIB format for further processing by Renderman.
To get started with Geomview, consult the
documentation or the printed manual in the Center library.
- Renderman -- Renderman produces high quality
still images of scenes described in RIB format. There is a library of
C routines one can use to produce a scene description in RIB format,
but often one works directly with the RIB file. Although Renderman is
not interactive, it is possible to do sophisticated shading and
- Softimage -- Starting up Softimage is like
climbing into the cockpit of a spaceship, except Softimage has more
enigmatic buttons. However, even if it is complex, it is nonetheless
an interactive 3D modeling environment, complete with
sophisticated tools for building up a scene description as well as
Softimage is only licensed on abel, nonabel, gauss and riemann. You
will want to start by perusing the documentation in the Center Library.
- Rayshade -- Rayshade is a public domain ray
tracing program. One writes a scene description file, specifying
lighting and rendering options, as well as the objects in the scene.
Objects must be describe in terms of constructive geometry,
i.e. constructed out of triangles, cylinders, cones, spheres, etc. To
get started, consult the printed documentation in the Center library.
Up: graphics resources
The Geometry Center Home Page
Created: Fri Sep 8 11:39:00 1995 ---
Last modified: Jun 18 1996