Computer Graphics:
Programming, Problem Solving,
and Visual Communication
Steve Cunningham
California State University Stanislaus and Grinnell College
PowerPoint Instructor’s Resource
Hardcopy
Preserving the results of your
graphics work
What kind of hardcopy?
• Who is your audience and how will they
be able to see your work?
– Digital image (online, presentation, …)
• 2D or stereo viewing?
– Print (article, newsletter, …)
– Film (film recorder, …)
– Video (online, television, presentation, …)
– 3D objects (prototyping, manipulation, …)
• Each can be created directly from your
work, but you treat them differently
Digital Images
• Can capture from screen or can use the
color buffer capture we described in the
code example in this chapter
• The raster (pixel array) these give can
then be saved in several file formats
• Each format has advantages and
disadvantages
Comparing File Formats
• TIFF
– Lossless, often quite large; some compression is
possible (LZW) but optional. If the file is intended
to archive your work, this is a very good choice.
• JPEG
– Uses a compression technique that is often lossy,
especially if you’re trying to reduce file size. Very
good on natural images, but can have serious
artifacts on lines and edges. If you want to use
jpeg formats, use a commercial tool to create and
decode your files.
Comparing File Formats (2)
• GIF
– Widely used format for the Web, but it uses the
LZW compression process so it should not be
used for commercial work. ((check out color
depth))
• Others
– PNG
• Gaining acceptance for the Web, no issues with patent or
with color depth
– Raw
• Simple file with pure RGB components, though some
variations (name?) also include dimensions. Can either
be interleaved (rgbrgbrgb…) or not (rrr…ggg…bbb…)
3D Images
• Compute two different 2D images as if
each were the view from a single eye
• Present them to the viewer in a way that
lets the viewer fuse the images to see a
3D image
– manual fusion (side-by-side)
– color fusion (anaglyph, Chromadepth™)
– temporal fusion (alternate eyes with
polarization)
3D Images - Manual Fusion
• Create two images, one for each eye’s
viewpoint
• Set the viewpoints carefully to mimic the
location of the eyes
• Display the images in side-by-side viewports,
spaced appropriately for the eye to merge
them
3D Images - Color Fusion
• Anaglyph process
– Create two images, one from each eye’s viewpoint, as in
manual fusion
– Compute a new image with the red channel from one view
and the blue and green channels from the other view
– View the image through red/blue glasses
3D Images - Color Fusion
• Chromadepth
process
– Described in the
Textures chapter
– Create a grayscale
image
– Add a 1D eye-depth
texture that is red
near and blue far
– View with diffusiongrating glasses
3D Images - Temporal Fusion
• Compute two images,
one from each eye’s
viewpoint, as in manual
fusion
• Present them alternately
through a reversable
polarizer, with the user
wearing polarized glasses
• CrystalEyes™ is one
such technology,
described in Chapter 10
Print
• Print involves adapting your images to
work with commercial printing techniques.
• Your image must be printed with several
single-color components, so it must be
separated into these components.
• The most common (and inexpensive)
approach is to use the CMYK color model
and separations
Print (2) -- separations
• Many commercial tools (e.g. Photoshop)
can create CMYK separations for you
Print (3) -- screens
• Once you have your separations, the printer
must create screens to control the ink on
press; you can’t print one color over another
• Options: traditional screens and stochastic
screens, but you should talk to the printer
about what can be done
• Stochastic (left) and traditional (right) screens
Film
• Film is not as important as it once was,
but it is still a good way to get highquality images
• Uses a digital film recorder to capture
an image one color at a time, using
filters
3D Objects
• There are several technologies that are
used to create 3D objects from
computation
• All rely on the STL file to define 3D
objects by specifying the triangles that
bound the object
• The file is read to create the boundary
of the object at each horizontal level
3D Objects (2)
• The techniques involve creating objects a
layer at a time, using
–
–
–
–
Paper
Wax
Powder
Plastic
• And the objects that are created can be used
to understand 3D models more fully
3D Objects (3)
• Four example technologies
Z-Corp
System
LOM System
Stereolithography
System
ThermaJet
System