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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] New oogl object classes
Hi, I've been thinking that it might be useful to have a couple of new oogl object classes. The first of these is a class for vector fields. At present you can either draw a vector field as a set of VECT's, but neither end of the lines is distinguished as a base point, if I'm applying a nonlinear transformation to a vector, I want to transform the base point, but use the derivatives of the transformation to find the new direction, if the vector is just a line both points will be transformed, not what is desired. The alternative is to pretend that the normals in an OFF etc, are tangent vectors, again we have problems with transformations as normals are actually bivectors, or the duals of vectors. The standard rules for transforming normals do not apply to vectors, for instance the mapping x > 2x effects normal and tangent vectors to the unit sphere differently. So what is required of a class for tangent vectors, 1) Each vector has a base point and direction componant, 2) the vectors may or may not be oriented, they may or may not be of unit length, they can be coloured; 3) some type of topological information might be useful, eg for a curve, you could have a set of tangents to the curve, including information about which order the vectors come in, this information could be similar to that used in an OFF but we might to use 3cells (tetrahedra) for vector fields defined over a region of space. The need for vector fields was first brought to my attention, by the question "Can you draw the set principal directions along a parabolic line on a surface?" "yep easy, this is just a set of lines", "now can you find where each of these lines insersect a plane, and draw the curve in the plane?", "Ah, not without cheating and knowing that the oogl object is actually suposed to be tangent vector along a curve." So wouldn't a class for tanget vectors be nice. The other class is that of ndimensional manifolds in R^m, not directly visulisable by geomview, but posibly useful for aplication programs, I just know there are pople in our department, who thing anything less than 6 just isn't intresting. A final comment on classes and objects, I'd realy like to include coments in with my data, describing exactly what the file represented, and still keep that information after the data has been read into geomview and saved. Ho hum, let us know what you think of these ideas, bye for now Rich


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