Sunday, September 25, 2011
I've looked at set-operations (union, difference, intersection) for octrees again. Previously I tried it with linear-octrees and visualization with python and VTK. Now I'm using a traditional pointer-based octree data-structure, and drawing with OpenGL VBOs. With the addition of a g-code interpreter, a user-interface, and an isosurface extraction algorithm (such as marching-cubes) this should converge [...]
Wednesday, August 18, 2010
Update: this figure shows the numbering of vertices(red), edges(green), and faces(blue). The arrows show the direction of the X-(red), Y-(green), and Z-axes(blue). Here the sides of the cube are not generated with Marching-Cubes, they are just extracted directly from the octree. Nodes are subdivided whenever the signed distance-field of the cutter indicates that the surface [...]
The speed of the new cutting-simulation code makes it possible to run it at a higher resolution than before. That makes the surfaces look smooth and nice. Alas, some problems still remain with holes in the fabric of reality mystically appearing and disappearing . There is an edge-flipping paper by Kobbelt et al. from 2001 which improves [...]
Saturday, August 14, 2010
This is my second attempt at a machining simulation where a moving milling tool cuts away voxels from the stock material. To save space an octree data structure is used to store the voxels, and to produce a nice looking surface you store the signed distance to the exact surface in each vertex of the [...]
Update 3: this leads slowly towards a better and faster cutting simulation. Here's an example with Tux: Update2: this looks slightly better now (a ball translated in a few steps towards the right). Image and c++ code by fellow OCLer Jiang from China. Update: in a cutting simulation the stock is updated by removing voxels [...]
Here's an initial test of octree-based cutting simulation: If you turn up the resolution to eleven, where it starts to be useful and not so grainy, the calculation of the tool-swept volume, which we subtract from the stock at each move, becomes too slow. See also octree operations. Download a short clip with a depth=10 [...]
If you number the octants in an octree using a 1982 scheme called Gargantini-code, and store the codes for only the black nodes in the tree in a list then that's called a linear octree. For quadtrees, there is a 1985 paper by Bauer with an algorithm for computing set-operations (intersection, union, difference) between two [...]
Recursion and 'divide-and-conquer' must be two of the greatest ideas ever in computer science. Threw together some code in python today for building an octree, given a function isInside() which the tree-builder evaluates to see if a node is inside or outside of the object. Nodes completely outside the interesting volume(here a sphere, for simplicity) [...]