Internal or External Surface Selection

chris_ICL

Hi, I am learning how to use Feature Scripts and I have come up against a bit of a road block that I'm sure must be relatively easy to solve:

I can't figure out how to tell whether a user selected surface is an external or internal face (for example a cylindrical surface could be either a hole or a shaft).

Please could someone point me in the right direction?

Thanks,

Chris

S1mon

I don't really know the answer, but because of all the edge cases, looking at convexity of the edges of the cylinder won't work. What might work is if you find the normal of the surface. I've never used it, but evFaceCurvature seems like it should get you a useful vector for maxCurvature and maxDirection. If you can identify the axis of rotation, you can see if the vector intersects the axis. There's also a canBeCylinder which you may need to use.

Just in case this isn't obvious, you will also need to make sure that the body is solid. If not, the surface normals could be deceiving.

chris_ICL

Thanks for your help S1mon, I will try those out and see how it goes.

antlu65

Late answer, but was just doing something similar with shafts/holes - adding incase someone has same question in future. As S1mon suggested, one can determine whether the selected face of a simple cylindrical/conical body is exterior/interior by using evFaceCurvature and checking the returned values of maxCurvature/minCurvature. An external face will have maxCurvature > 0, an interior face will have minCurvature < 0.

const curvatureResult = evFaceCurvature(context, {
    "face" : qFace,
    "parameter" : vector(0.5, 0.5)
});
const isExterior = curvatureResult.maxCurvature > 0 / millimeter;
// const isInterior = curvatureResult.minCurvature < 0 / millimeter;