On g+, John Baez linked to work by Henk Hilhorst on the probability of finding voronoi cells with n sides in a poisson voronoi diagram. A poisson voronoi diagram has point sites randomly and uniformly distributed, like this: Here's the distribution I came up with, after counting the edges for each voronoi cell from 200 [...]
Saturday, December 3, 2011
At some point I'm going to need random simple polygons for testing my voronoi diagram code. CGAL includes a function random_polygon_2 which uses the "2-opt" heuristic (see Auer&Held-1996). I wrote a minimal boost::python wrapper around this function in order to test it and draw the polygons using vtk. Here are some examples of random polygons [...]
Monday, November 21, 2011
Update3: version 11.10-148 now goes to 16k line-sites without errors or warnings: Update2: This diagram with 8k vertices clearly has errors: Update: Version 11.10-141 now copes with 4k random segments. But I don't know of any smart way to check the diagram for correctness.. Constructing the vd for random (non-crossing) line-segments is a reasonable stress-test [...]
Sunday, November 13, 2011
I've made some more progress with my voronoi diagram code. I described the topology-oriented incremental algorithm earlier here (point sites) and here (line segments). When we want to add a new site (a point or a line-segment) to the diagram we should find a tree of to-be-deleted vertices/edges (red), create new (green) vertices on all [...]
This shows the voronoi-diagram of a single line-segment together with an increasing number of point-sites. (watch it in 1080p on youtube!)
Saturday, October 29, 2011
I've made some progress with my voronoi diagram code: Sites/generators in yellow. Line-edges in cyan, parabolic edges in red. Note that the parabolic edges are split at their apex, i.e. the closest point to the adjacent site. Some problems with hooking up the half-edges of the two new faces that are associated with a new [...]
Saturday, October 22, 2011
Seen on IRC yesterday. The python-scripting capability of FreeCAD(a Qt + OpenCascade based free CAD-program) allows calling opencamlib for toolpath-calculations much like is done from HeeksCAD/CNC(a Wx + OpenCascade based free CAD-program). Cool. Another screenshot with waterline:
Here's a simple test program using LibQGLViewer (screen capture with xvidcap). The vertex array and the index array that OpenGL draws (using glDrawElements) are held in a GLData class which holds a mutex. The Viewer class locks the mutex while drawing, and the worker-thread locks the mutex while updating the data. Here the worker task [...]
I've looked at this example from 2003 and converted it to something that compiles with qt4.7. Here: https://github.com/aewallin/sandbox/tree/master/qt_opengl_threads Each window is a QGLWidget with its own QThread associated with it that does the drawing. That means the UI should stay responsive despite heavy processing in the threads. I wonder if this can be made to [...]
Saturday, October 1, 2011
Based on Mark Pictor's cam-occ work I've been able to use the emc2 g-code interpreter 'rs274' binary that gets built during an emc2-build. It reads g-code files and outputs 'canonical' motion commands (see e.g. "The NIST RS274/NGC Interpreter - Version 3"). I'm positioning the tool at densely sampled points along each move, and subtracting it [...]