I think I got the picture. Thanks for the useful comments. Ted
P.S. By the way, the hard copy of David's book is still not available :( >Ok, "invalid positions" will separate the boundary points from the >volume points but in respect to the boundary conditions the boundary >points are not equivalent. Is it possible to mark the boundary points >with a tag/property that specify the type of boundary conditions >imposed on the surface this point belongs? > >Thanks for your comments, >Ted > Sure, just create multiple different components each carrying a particular type of tag/property and attached in a one-to-one correspondence to each and every position (including interior positions because you have to retain the same structure for each component attached to a field). Of course, the interior points don't have a tag, so make it either a bogus number like -99 or something to preserve the presumed numeric nature of the tag elements. If they are strings, then use "NA" or something. The invalid positions knock these out anyway when you go to display the tags (so only the boundary tags show up). That's why I proposed invalids. So you have something like: x, y, z, data1, data2, tag1, tag2, invalid tuple for each and every point in the data set. data1, data2,... are the various data values you measured (temp, pressure, etc.) and can be scalar or vector as desired. tag1, tag2, .... are various properties. Each column must have consistent type, but as mentioned, tag1 could be numeric and tag2 string. invalid is the invalid marker already discussed. If you think of the positions as the base array that "carries" all the other components, then imagine laying a sheet of data over these positions. This sheet must have a data entry to correspond with every position (position-dependent data). Then, the invalids sheet also has a value for every position, but the way DX utilizes this sheet is to knock holes out where invalids are 01. This takes out the underlying position and all associated data/tags/etc with that position, either permanently (if you cull) or temporarily (treating it as a 'bandpass' filter if you like). If David's book doesn't answer all your questions, my company does do DX consulting for agencies like yours. (:-) Chris Pelkie Vice President/Scientific Visualization Producer Conceptual Reality Presentations, Inc. 30 West Meadow Drive Ithaca, NY 14850 [EMAIL PROTECTED]
