Draw Your Data in 3D with HoloDraw

HoloDraw is free VRML generator software that helps you make rotating, fly-through and fly-by 3D images from your data. Downloads are available for Unix, Mac or Windows. The images you make with HoloDraw can be viewed on a GeoWall in stereo 3D, or in a web browser with the free Cortona plug-in or Cosmo Player.

HoloDraw is designed to read many common data formats including X-Y and X-Y-Z points, lines or surfaces. You can also represent a fourth attribute as a color. For example, the X-Y-Z values might be the hypocenter of an earthquake, while you use color to represent the magnitude, date, or some other type of information about each quake (Figure 1). It can be very easy to convert your data to HoloDraw format. For example, a HoloDraw file to plot three points might look like this:

   point:270.3 9 -2790
   point:268.0 0.4 -2415
   point:270.5 6 -2760

Several HoloDraw programs exist to help format your data, but often you can do it with a single Unix command such as sed or awk. Then, use another HoloDraw program to output your data in VRML 1 or VRML 2 format for the GeoWall, or VRML 2 format for web browsers.

HoloDraw can also work with Generic Mapping Tools (GMT) maps and scripts. Figure 2 shows a GMT pscoast map plotted above other (non-GMT) data, using HoloDraw. The GMT map can be fully rotated and zoomed in real time stereo 3D along with the rest of the image. Figure 3 shows a GMT surface plot integrated within a HoloDraw 3D section of Earth's interior. HoloDraw also recognizes GMT Color Palette Tables (".cpt" files.)

As the figures illustrate, HoloDraw can work with flat map projections, spheres, or sections of spheres. You can even have multiple spheres within a cube's coordinate system, as seen in this true-scale diagram of Earth and its moon.

Although HoloDraw processes graphical data, it does not have a graphical user interface. Some people find a graphical interface easier to learn the first time they are doing something new. However, experienced users may prefer to write scripts to automate their work. Like GMT, HoloDraw is designed for the latter type of user. HoloDraw is driven by commands that can be scripted, or can come from another program. This means programmers can generate VRML without having to bother with all the details of VRML syntax. HoloDraw provides a "quick and dirty" interface from your data or program to VRML.

HoloDraw is also intended to build on the strengths of Unix. The HoloDraw format interfaces easily with standard Unix tools such as awk, grep and sed. HoloDraw embraces powerful Unix concepts such as

• modularity
• small simple programs that act as filters to transform data
• pipelines using standard input, standard output and standard error
• scripted commands

While you can run the HoloDraw programs on other computing platforms, a Unix or Unix-like environment is recommended for maximum benefit.

Finally, HoloDraw is intended for data visualization, not creative drawing. If you want to sketch a lovely scene, those point-and-click drag-and-drop graphical-interface programs are probably the thing for you. If you have ten million data points you'd like to plot in 3D, and you'd rather have the computer do all the work and spare your mouse, welcome to HoloDraw.