See which faces are affected by polyChipOff?

[Erik Spellerberg]

I am extracting objects using mel.eval('performPolyChipOff 0 0;'), but I don't know which of the resulting meshes is the one belonging to the faces i selected previously. Maya does not always order them the same way. So I'm thinking I can check which faces are affected by the resulting polyChipOff node but I don't know how to dig out that information.

[Erik Spellerberg]

Also I'm using pymel for this.

[fruit...@gmail.com]

I'm not sure I understand what you want to achieve, but can't you use the python version instead of the mel one ?
a = cmds.polyChipOff(dup=False)
b = cmds.polySeparate(your_mesh)

this way, you get a proper return value in a and b that you can work with.
What do you need to do exactly ?

[Erik.Spe...@starbreeze.com]

This is what I want to achieve: https://i.imgur.com/ZlZIe3t.jpg

Using polySeparate causes a bunch of problems. I get this result: https://i.imgur.com/917NFMA.jpg (and yes using the the mel command gives the exact same result)

As you can see, Maya gives me three objects and I do not know which one is the original sphere. Sometimes its the one named PolySurface1, on a different model it might be the last one. Maya is not consistent.

I did sort of solve it though by duplicating the entire mesh and deleting the inverted selection. However I do not really like this method as it can be slow. So I would like to be able to read the node data and just SEE what faces

[Marcus Ottosson]

See the inputComponents attribute of the polyChip node.

cmds.getAttr("polyChip1.inputComponents")
# Result: [u'f[202]', u'f[239]', u'f[241]'] #

Example

sphere, _ = cmds.polySphere()
cmds.select(
    sphere + ".f[202]",
    sphere + ".f[239]",
    sphere + ".f[241]"
)

chip = cmds.polyChipOff()
faces = cmds.getAttr(chip[0] + ".inputComponents")
cmds.select(
  sphere + "." + faces[0],
  sphere + "." + faces[1],
  sphere + "." + faces[2]
)

Normally, components affected by polygon modifications - like soft modification, skinning, extrude etc - are stored in an invisible objectSet node, which I was looking for at first. But as it didn’t have any, I knew it must have been stored internally. In this case, it looks to be a compound string attribute.

​

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[fruit...@gmail.com]

Alternately, and especially since speed seems to be a concern, what you can do is to re-write your own extract/duplicate command with python api. This is what I use instead of maya commands, it takes about 50lines to can get all the infos you need to create a new polygon. And, surprisingly, re-creating the poly instead of using maya nodes give you a tremendous gain of speed, especially if you work on heavy meshs and extract many faces on the same object.