ESM4714
Scientific Visual Data Analysis and Multimedia
Exercise #13: Lorenz 3D Attractor Map

Objective:
Create a 3D visual display of a Lorenz attractor and study the structure-time relationship by manipulating a color table (palette), where one portion of the color palette is used to represent time and another portion of the color palette is reserved for plotting background and axis line colors.

1. Logon onto mercury -> pluto.smvc.vt.edu at the VT-CAVE classroom (SMVC).

2. Mount your optical disk (see procedure for mounting scsi devices).
3. Go to the ESM4714/examples directory.

4. Locate the directory that contains PV-Wave procedure files for generating an image of a Lorenz attractor and corresponding color maps and then start wave.

   viz?% cd /opdisk/examples/color/lorenz

   viz?% ls -lag

   viz?% wave

   wave>_

5. File transfer the rainbow.pal color palette from the Mac to the Sun (this color palette can be found in SciViz Tools/NCSA Tools/PALEDIT on viz3 or viz4).

6. Convert this Mac color palette to a Sun color palette.

   viz?% itoa.x < ranibow.pal > mac_rainbow.ascii

   viz?% wave

   wave> device,pseudo_color=8    (Note: Setup for Sparc20s in Viz lab)
   

   Depending on your particular graphics hardware configuration, other or different devices
   may need to be declared before proceeding. Consult PV-Wave documentation Appendix
   on "Output Devices and Window Systems". To determine your particular graphcis
   configuration, at the wave prompt enter:   wave> info,/device

   wave> adj_ct_mactosun,240

   **** Read-in Mac color-map filname ****

   : mac_rainbow.ascii

   **** Write-out Sun color-map filename ****

   : sun_240_rainbow.ascii

7. Check the color palette just created.

   wave> l_color,240

   **** Enter file name for color map to be loaded ****

   :sun_240_rainbow.ascii

   wave> palette

   The PV-Wave command palette generates an interactive color palette shown below, where
   the Red, Green, and Blue intensities can be manipulated with the left mouse button. Two
   colors at the end of the color spectrum are set to "255" (white) and "0" (black) and are
   reserved for plotting grid lines, coordinate axes, and background in the PV-Wave procedure
   files m_bar.pro and m_lorenz.pro. These two reserved colors are not part of the rainbow
   color palette that is used by m_lorenz.pro to plot time as color.

   Although these end colors can be set with the PV-Wave procedure file palette, in this example
   the white and black colors were originally set in the color palette mac_rainbow.ascii, where
   256 pixels (0-255) were used to define the Red, Green, and Blue color palette. The PV-Wave
   procedure file adj_ct_mactosun.pro rescaled the 256 (0-255) colors in the mac_rainbow.ascii
   color palette to 240 (0-239) colors in the sun_240_rainbow.ascii color palette.

   

8. Create a color bar with 240 r-g-b colors, but reserve the 239-th and 0-th pixels in the color palette for background and line colors.

   wave> m_bar,240,0,239

   **** Enter filename for color map to be loaded ****

   : sun_240_rainbow.ascii (where pixel-0=white ["256"] and pixel-239=black ["0"])

   

9. Draw a Lorenz attractor image using 240 (0-239) colors with a black axis and a white background:
   pixel-0=white (background) and pixel-239=black (axes).

   wave> m_lorenz,240,0,239

   **** enter filename for color map to be loaded ****

   : sun_240_rainbow.ascii

   

10. Modify the color map so that pixel-0=black and pixel-239=white.

    wave> m_color,240

    **** Enter file name for altered color map ****

    : sun_240_mod_rainbow.ascii

    **** Use existing color / Choose new color (0/1) ****

    : 0 (an adjustable color palette appears, see above image)

    Change the 0-th pixel from white to black and the 239-th pixel from black to white.

    

    The Lorenz attractor image, shown above with a white background, is modified and shown below.

    

    Note that this change in background and axis line colors did not effect the colors on the Lorenz
    attractor. The m_lorenz.pro PV-Wave procedure file is constructed so that the end colors on
    the rainbow color palette are reserved for the background and axis line colors and the rainbow
    colors are reserved for plotting time on the attractor plot. This is an example of how a special
    color palette can be constructed so that different portions of the color palette can be used for
    different purposes.