README 8/1/90 NCSA Isosurface Visualizer _______________________________________________________________________________ BEFORE YOU BEGIN Please read the README.FIRST file - found at the root level of this server - for general information and instructions on unarchiving and uncompressing files. The README.BROCHURE also contains helpful descriptions of this and other software offered on the ftp server. _______________________________________________________________________________ NCSA ISOSURFACE VISUALIZER NCSA Isosurface Visualizer is a 3D visualization tool which allows a user to generate 3D surfaces of constant value in a simple manner. Input data must be in the form of a single 3D array of scalar data stored as a Scientific Data Set (SDS) in an HDF file. As output, the program can generate a VSet in an HDF file and/or an object file. Both of these files contain the polygons that make up the isosurface. The VSet may be viewed by a program such as NCSA PolyView. The object file is a simple ascii file of vertices and connectivity; and it may be viewed by programs such as Personal Visualizer from Wavefront Technologies, Inc. If the program has been compiled on a Silicon Graphics Iris, then ISOVIS also gives you the option of displaying the isosurface within ISOVIS. You can control color selection, scaling, rotation, etc. You can also save the resultant image as a raster image in HDF format. ISOVIS has been set up as a non-interactive batch utility to enable users the ability to create 3D animations from time-dependent data with little effort. Isosurface Visualizer was written at the National Center for Supercomputing Applications (NCSA) located at the University of Illinois, Urbana-Champaign. The software was developed by NCSA's Software Development Group and NCSA's Visualization Services and Development Group. _______________________________________________________________________________ GENERAL NOTES By typing just the name of the program, it will respond with a list of available options for your particular machine. The basic command line format is: isovis [-options] <3d_sds.hdf> Where [-options] can be zero or more options to isovis, <3d_sds.hdf> is the name of a three dimensional data set which must be a Scientific Data Set in a NCSA HDF formatted file, and is the particular floating point value of the isosurface that you are interested in. The options fall into two categories: general options and SGI options. The general options are: -def - print default values -p - print status during execution -vset - create an HDF file containing a VSet of the polygons -obj - create an ascii .obj file containing the polygons The SGI options are: -bc - set the background color of the window -d - toggle the display on and off -k - set lighting characteristics -lc - set light color -ll - set light location -ns - set specular exponent -ntsc - use a window in NTSC position -o - save the image as an HDF 24 bit raster image -r - rotate the image -s - scale the image -t - transate the image -v - set the window location The range of values for '-bc' and '-lc' are from 0.0 to 1.0 and they specify the RGB colors. The values for '-r' are in degrees, and the values for '-ll', '-s', and '-t' are in unspecified units. An example command line might be: isovis_sgi -vset demo.hdf -bc 0. 0. 1. -o img.hdf -r 45. 45. 45. \ dataset.sds 5.0 The above command would generate an isosurface of threshold equal to 5.0. The isosurface would be displayed in a window on the SGI with the background color set to blue. The image would be rotated by 45 degrees in x, y, and z directions. The resultant polygons would be saved to an HDF file, named 'demo.hdf', containing a VSet (which could be viewed by a program such as NCSA PolyView), and a 24 bit raster image would also be saved in another HDF file named 'img.hdf'. Example three dimensional SDS HDF files can be found on the NCSA Anonymous FTP server (ftp.ncsa.uiuc.edu/128.174.20.50) in the directory XDataSlice/samples.