William Cauchois wrote: > Hello, > > William forwarded this thread to me. I've been working on the > parametric_plot3d code under his guidance, and I think I could > implement this feature, the option to specify points for exclusion > from a plot. Last night I investigated an implementation that simply > removes all faces whose vertices do not satisfy the region function > (this would be in ParametricSurface.triangulate, before the data is > passed to Jmol or Tachyon). > > Jason, it sounds like you are familiar with the code. Do you think > that that method should be sufficient, or is something more complex > necessary? Of course, I can write the implementation and then see for > myself, but I wouldn't want to waste effort. > >
I'm not familiar with the code. I dug through it once or twice trying to track something down (and because I was curious). Robert Bradshaw is the real person to ask. Does that implementation give jagged edges? It seems like it would. I'm thinking of something like the marching cubes algorithm instead, where you approximate where a surface crosses the edge of a cube by linear approximation. With a True/False function, we don't have any sort of approximation we could use. However you could do something of a binary search to narrow down where the edge crossed the region boundary In other words, if you had a triangle edge that crossed the border of the region, I wonder if you could subdivide the edge once or twice to try to get a finer approximation to the region boundary. Try to find out better where exactly the edge crossed the region boundary via a binary search and split the triangle at your best guess, keeping as much of the triangle as you can. Just a thought. Of course, you'd probably want to put in a limit to the subdivisions, something like the subdivisions of 2d plots. Thanks for working on this! I've wanted this functionality for a long time! Jason --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sage-edu" group. To post to this group, send email to sage-edu@googlegroups.com To unsubscribe from this group, send email to sage-edu+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-edu?hl=en -~----------~----~----~----~------~----~------~--~---
