c++ - pcl中，PrincipalCurvatures 和 Normal中的curvature的关系是什么？

Question

PrincipalCurvature的结构

{
    principal_curvature_x
    principal_curvature_y
    principal_curvature_z
    pc1
    pc2
}

Normal中也有个curvature

{
    nx
    ny
    nz
    curvature
}

那末这两个结构中的曲率到底有什么不一样？

Answer 1

It seems that the curvature of PrincipalCurvature is not the curvature in the mathematical definition. It seems to be calculated through the neighborhood of points and least squares. The curvature in Normal should be calculated using the co-defense matrix of the neighborhood point set + singular value decomposition. .
This is the result I displayed using addPointCloudPrincipaCurvature under the visualization class in pcl

The blue line is perpendicular to the green line (they are both line segments, after zooming in), but it is still unclear what it means?