Updated integral_mean_curvature function

[yajushikhurana]

The integral_mean_curvature (IMC) function did not agree with the analytical value for non-convex objects such as a torus and an annulus. The angle in the function needs to have an appropriate sign to detect concave angles. This code corrects that error and also adds a test function for IMC to test for non-convex objects.

[mikedh]

Awesome thanks for the PR and test! Quick question, do we need another function and attribute for vector_angle_with_sign? Couldn't one use the existing mesh.face_adjacency_convex value?

In [12]: signs = np.array([-1.0, 1.0])[m.face_adjacency_convex.astype(np.int64)]

In [13]: angles = m.face_adjacency_angles * signs

[yajushikhurana]

Thank you for the review. You are right! I initially added vector_angle_with_sign to handle signed angles manually, but I overlooked the fact that mesh.face_adjacency_convex can provide what’s needed. I've updated the PR.

[mikedh]

Looks great thanks for the update!