Usage: vgp [-n] [-v] [data-file1 data-file2 ...] First of all: THIS PROGRAM REQUIRES MOTIF OR LESSTIF! What is vgp? Vector Globe Projection is a tool for engineers, scientists, or anyone that deals with series of R3 (3-dimensional) vectors. (A vector of vectors so to speak.) The usual case is a set of these n x 3 matrices with one representing time and the others representing other signals like momentum or velocity, changing with time. It could also represent a partial attitude, by the vector representing e.g. the Y-axis of the body with respect to an inertia frame. Throughout this document I will refer to the series as a time history which is most usually the case. vgp displays the entire time history of the vector as the path it would follow on a sphere. This time history can be animated as a vector starting at the center of sphere and pointing toward the current point. The current row number of the data is displayed in the top right corner. What are the controls? The left mouse button will rotate the sphere. The right button will translate the sphere. The middle mouse button will create a zoom rectangle that should be dragged around the region of interest and a zoom-in will occur. To zoom-out either push the "full size" button or shift-middle mouse button. The "start" button will start the animation. Data Format: The data format consists of three space delimited columns of ASCII text floating point numbers. Examples: vgp data/orbit.data data/earth.dat data/latlon.dat I've included some example data files to demonstrate some of the concepts. The data is in the 'data' sub-directory. The first is named 'spiral.dat'. This is a simple spiral which is good demonstration of the animation. The file 'earth.dat' is the outline of all the major land masses. This is only for show purposes and not the point of the program. The last two files were generated by the SWAS spacecraft simulation. The file 'cone.dat' demonstrates the solar array axis of the spacecraft acquiring the sun and coning about it. The file 'map.dat' demonstrates the mapping mode of the spacecraft along the instrument bore-sight. This data must be zoomed in on a lot! Look for the busy part of the picture. This can be found be starting the animation and rotating the sphere until you find the point were the vector spends the most time. Zoom in on this area repeatedly and you will notice the finer and finer details of the motion. What vgp is not: Since I work with spacecraft many people urged me to make the sphere the earth and animate a spacecraft going around it. But this program is meant to be more general than that. This program will work with any series of 3D vectors. Also, from an engineering perspective, I feel this program, the way it is, gives the important information. What I would like to add to vgp: * Athena Widgets: I believe in the free software creed and would like people to be able to use my program without the proprietary Motif Widget set. However, with the program working now with LessTif, this may never happen. * Keyboard Events: I couldn't figure out how to get keyboard events either. Left the code in there though. * File format: The file format now is just a list of three columns of ASCII text. Does anybody have a better idea that's as flexible? I could do Matlab binary quite easily. If anyone wants to help me with these things it would be greatly appreciated. I recieved a patch file for vgp 1.0 to make it compile with Open Look. I had orginally planned to include those changes in this version. However, Open Look seems a bit passe nowadays. If there's much interest I can get it to work in Open Look. Send Bugs, suggestions, help to: Rick Niles niles@axp745.gsfc.nasa.gov
