Fun with batches and generators.

[tonious]

As part of playing around with chamfers, I've been making looking at meshes up close. I could just save the result, and view that in something like meshlab. But where's the fun in that? It would be easy to... Look at each triangle, place a sphere at each vertex, hull those in pairs to make line segments and then union the whole thing together. That should be fast, right?

Unoptimized:

Bundling code took 0.02 seconds
Exporting Manifold object as mesh:
  Triangles: 10,628
  Bounding Box: X = 100.2 mm, Y = 100.2 mm, Z = 50.2 mm
  Genus: 0
  Volume: 393.02 cm^3
Total glTF nodes: 1
  Manifold meshes: 1
Manifold took 2.85 seconds
Exporting GLB took 0.01 seconds
Exporting 3MF took 0.07 seconds

Deduplicating segments, and performing unions in batches:

Bundling code took 0.02 seconds
0/1074 edges processed
500/1074 edges processed
1000/1074 edges processed
1074/1074 edges processed
Exporting Manifold object as mesh:
  Triangles: 8,156
  Bounding Box: X = 100.2 mm, Y = 100.2 mm, Z = 50.2 mm
  Genus: 0
  Volume: 393.02 cm^3
Total glTF nodes: 1
  Manifold meshes: 1
Manifold took 1.08 seconds
Exporting GLB took 0 seconds
Exporting 3MF took 0.05 seconds

This second run is faster, even though it's forcing a mesh evaluation every 500 segments.

Check it out!

meshTriangleWireframe() accepts a Mesh object, and returns a Manifold representation of the triangle mesh.

batchUnion() is a drop-in replacement for Manifold.union() with a few creature comforts. It prints feedback as each batch is completed, via a callback so it can be customized. It will accept iterators as well as flat arrays, which is a side-benefit of using generators.

And now I don't have to leave the browser to check my work.

[elalish]

That's amazing! Though, would you be sad if I told you it's probably easier to hack <model-viewer> to make it render edges? It's just three.js after all, which does all the things. I should probably just do that and put in a switch...

[tonious]

Here are some faces, then 😀

Live example here

Next step -- figuring out why I can't package this through jsDelivr/npm.

[tonious]

And that's sorted. Here's a demo and the corresponding package source.

[elalish]

Dang, that's beautful! And probably a fair bit fancier than I can manage in <model-viewer>. However, if you're looking to make it fast for meshes with larger edge counts, I'd recommend instead of hulling, just make a transform that scales a cube to the proper long, thin edge based on those two segment coordinates. Then you can just make a single cube manifold for all the edges and just do a GLTFNode with a transform for each. We call this instancing in the biz...

[tonious]

And now with normals. (Demo)

Running calculateNormals() before and after subtract:

An inverted normal?

Getting normals for either input, and then both:

[elalish]

We now have an edge rendering switch in ManifoldCAD: #1624

Your tool for visualizing normals looks quite handy though, especially for debugging!