Convex/Concave Hull
The
Convex Hull
node is a very useful in Geometry Nodes, but what if we can exclude certain geometry to produce more complex geometry?
Example: the red spheres are inside the hull and the green one on the outside to produce a shape not yet possible to produce with the
Convex Hull
node.
I imagine another input on the
Convex Hull
node, as seen below, for the geometry which has to be excluded. The bottom input is not required, the top should be. Mockup of what it could be like:
6 Comments
seems a bit ironic that the result mesh isn't convex... doesn't that defeat the entire purpose of the convex hull node?
I know it isn't convex anymore, but how else would you call it?
sounds like the set-up for a joke "what do you call a bicycle with four wheels"
in all seriousness, what you're wanting to create is called a concave mesh, or complex mesh. I'm not really sure what you're trying to accomplish with this proposal, it almost seems like you're really wanting metaballs?
Metaballs are something entirely different. I think my proposal is indeed getting some node which outputs a convex and concave mesh, using two inputted geometries.
Here's a video of what I sort of want: youtu.be/PeEAkzKlI08
This example is done in QGIS.
I had to deal a lot with convex and concave polyhedra in procedural level generation for the Quake branch of game engines.
As already pointed out, you'd get a concave hull there... but I personally don't know of a sound and fast algorithm to actually do in 3D what you've illustrated in 2D.
If you take a cloud of points, its convex hull is pretty well defined. Now, working with "outside points" in that could could bring various problems. Which area/side of the convex hull will be affected by a point? If it has thin or small triangles, would you get just a really thin bore hole? How to decide how to re-triangularize the border around each hole?
It is possible that the thing you have in mind can't be defined and generalized clearly enough to be taught to a program, unfortunately. :|