comparison toolboxes/FullBNT-1.0.7/KPMtools/polygon_intersect.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function [is,S] = isintpl(x1,y1,x2,y2)
+% ISINTPL Check for intersection of polygons.
+%	[IS,S] = ISINTPL(X1,Y1,X2,Y2) Accepts coordinates
+%	X1,Y1 and X2, Y2 of two polygons. Returns scalar
+%	IS equal to 1 if these polygons intersect each other
+%	and 0 if they do not.
+%	Also returns Boolean matrix S of the size length(X1)
+%	by length(X2) so that {ij} element of which is 1 if 
+%	line segments i to i+1 of the first polygon and 
+%	j to j+1 of the second polygon intersect each other,
+%	0 if they don't and .5 if they "touch" each other.
+
+%  Copyright (c) 1995 by Kirill K. Pankratov,
+%       [e-mail].
+%       06/20/95, 08/25/95
+
+
+ % Handle input ...................................
+if nargin==0, help isintpl, return, end
+if nargin<4
+  error(' Not enough input arguments ')
+end
+
+ % Make column vectors and check sizes ............
+x1 = x1(:); y1 = y1(:);
+x2 = x2(:); y2 = y2(:);
+l1 = length(x1);
+l2 = length(x2);
+if length(y1)~=l1 | length(y2)~=l2
+  error('(X1,Y1) and (X2,Y2) must pair-wise have the same length.')
+end
+
+ % Quick exit if empty
+if l1<1 | l2<1, is = []; S = []; return, end
+
+ % Check if their ranges are intersecting .........
+lim1 = [min(x1) max(x1)]';
+lim2 = [min(x2) max(x2)]';
+isx = interval(lim1,lim2);  % X-ranges
+lim1 = [min(y1) max(y1)]';
+lim2 = [min(y2) max(y2)]';
+isy = interval(lim1,lim2);  % Y-ranges
+is = isx & isy;
+S = zeros(l2,l1);
+
+if ~is, return, end  % Early exit if disparate limits
+
+ % Indexing .......................................
+[i11,i12] = meshgrid(1:l1,1:l2);
+[i21,i22] = meshgrid([2:l1 1],[2:l2 1]);
+i11 = i11(:); i12 = i12(:);
+i21 = i21(:); i22 = i22(:);
+
+ % Calculate matrix of intersections ..............
+S(:) = iscross([x1(i11) x1(i21)]',[y1(i11) y1(i21)]',...
+               [x2(i12) x2(i22)]',[y2(i12) y2(i22)]')';
+
+S = S';
+is  = any(any(S));
+