Centroid of a convex surface is outside of it

[Grasshope (Ji)]

I have the following brep surface whose centroid is obtained using the surface evaluation component (with reparameterization). However, this centroid falls outside the surface, unlike the center obtained using the area component.

May I ask why the centroid is not located inside the surface, and how to solve this kind of problem?

Thanks.

centroid of a convex surface is outside of it.gh (9.8 KB)

[ferry59]

Its beacuse it is a trimmed surface:

Re_centroid of a convex surface is outside of it.gh (14 KB)

[martinsiegrist]

I’m using this script to shrink trimmed surfaces in Grasshopper:

c_shrink_trimmed_surface.gh (5.6 KB)