Function ip = selectpointswithinplanes(p,b,tol) returns a list of indices to the given points which are "within" the given boundary planes, or are at the "inside" of the given boundary planes. Each boundary plane is defined by three points on it; the normal calculated by the three points is pointing outwards, i.e. defining the "outside" of the plane. Input variables p and b have three columns containing the x,y,z coordinates, respectively. Three consecutive rows in b define a boundary plane. Input variable tol is a real scalar and represents the absolute tolerance value by which the planes are virtually moved outwards. Output variable ip is a list of indices to p. The validity of the input is not checked! (c) 2026 fabien van mook 2026.08.20 release of this file within package "fvm-geometry" under GNU GPLv3+