Removing tiny bodies from a larger shape

[kriho]

Hi everyone,

has anyone found a way to detect and remove tiny bodies from a larger shape?
I am generating a model from user input and in some cases small "chips" of a model are left floating around. These bodies all have very short edges. I need a method of finding and removing the "chips" from the main shape.

If anyone found a way or has an idea on how to do this, please let me know! Thanks!

[raydeleu]

Are these edges and pieces inside another shape? I think that opencascade.js has an additional function to remove internal edges. The application CascadeStudio, which is also based on opencascade.js, has a function called RemoveInternalEdges(shape, keepShape?). If you look into the code of OpenCascade you can probably derive which OpenCascade function is used to perform this functionality. As far as I know this function is not exposed in Replicad as normally these remnants should be removed by the modelling function automatically.

[kriho]

The bodies are floating outside of the main shape. The are all fully closed.

[sgenoud]

Is your model a mesh that you then import within replicad?

[kriho]

Everything is generated with replicad.
Thanks by the way - I was working with OpenSCAD before and I truly enjoy working with replicad now! I really like the interface and had very few issues so far!

[sgenoud]

My guess is that you do a bunch of boolean operations that leave more than one shape, right?

Then you might try to iterate over all the shapes of type body within your compound shape and remove the one you don't want. There are no exposed APIs to list of the "solids" of a generic shape - you could hack by getting inspiration from here

[kriho]

Correct. Thanks for the help, I got it working with your hint.

const subShapes = shape._listTopo("solid").map(s => new rep.Solid(s));
for(const subShape of subShapes) {
  const bounds = subShape.boundingBox;
  if(bounds.width < threshold || bounds.depth < threshold) {
    shape= shape.cut(subShape);
  }
}

This can lead to a lot of additional boolean operations. Is there a way to just "remove" the filtered sub shapes from the shape?

[msngupta]

I wonder if compounding the shapes to be cut using makeCompound, then performing a single cut operation on the compound, would be faster?

[kriho]

As I understand it, I already have a compound shape and the goal is to remove some of of its shapes. The snippet above works by cutting (boolean operation) the compound shape with one of its shapes. That feels wrong - not sure if that case is detected under the hood or if the boolean operation is performed. I have no solid data but it feels slower now.

[sgenoud]

You could probably try something like that:

const subShapes = shape._listTopo("solid").map(s => new rep.Solid(s)).filter(subShape => {
  const bounds = subShape.boundingBox;
  return bounds.width >= threshold && bounds.depth >= threshold
})

You would then have a list of shapes you can compound together (or not depending on your use case)