HPR.rar_HPR_hidden point removal

function visiblePtInds=HPR(p,C,param) % HPR - Using HPR ("Hidden Point Removal") method, approximates a visible subset of points % as viewed from a given viewpoint. % Usage: % visiblePtInds=HPR(p,C,param) % % Input: % p - NxD D dimensional point cloud. % C - 1xD D dimensional viewpoint. % param - parameter for the algorithm. Indirectly sets the radius. % % Output: % visiblePtInds - indices of p that are visible from C. % % This code was written by Sagi Katz % sagikatz@tx.technion.ac.il % Technion, 2006. % For more information, see "Direct Visibility of Point Sets", Katz S., Tal % A. and Basri R., SIGGRAPH 2007, ACM Transactions on Graphics, Volume 26, Issue 3, August 2007. % % This method is patent pending. dim=size(p,2); numPts=size(p,1); p=p-repmat(C,[numPts 1]);%Move C to the origin normp=sqrt(dot(p,p,2));%Calculate ||p|| R=repmat(max(normp)*(10^param),[numPts 1]);%Sphere radius P=p+2*repmat(R-normp,[1 dim]).*p./repmat(normp,[1 dim]);%Spherical flipping visiblePtInds=unique(convhulln([P;zeros(1,dim)]));%convex hull visiblePtInds(visiblePtInds==numPts+1)=[];