How to extract the boundy of the hole in pcl?

Question

There is a point cloud on a plane with a circle hole,i wander how to extract the points of the hole to make me fit the 3D circle?

Answer 1

When using the pcl::BoundaryEstimation<pcl::PointXYZ, pcl::Normal, pcl::Boundary> class. It is better to project the point cloud to the xoy plane,not the plane using ransac to fit.

It's a little bit weird, i don't know how the class work in pcl, isn't it using PCA method to calculate the boundary?Hope someone can give a explanation.

Use the plane fitted by ransac method to project(the boundary):

Use the XOY plane to project(the boundary):

Or use pcl::ConcaveHullpcl::PointXYZ class，which can also solve such problem.