For my problem I need to extract the lower convex hull of a set of 3D points (X,Y,Z). In Matlab, one can find the convex hull using the convhull function as follows: K = convhull(X,Y,Z).
Could anybody please suggest me a way to extract the lower hull from the convex hull? I found many references/code for 2D case but for 3D it seems to be not very popular (I'm new to computational geometry).
Thank you in advance for your help.