clipLine3d

CLIPLINE3D Clip a line with a box and return an edge.

   EDGE = clipLine3d(LINE, BOX);
   Clips the line LINE with the bounds given in BOX, and returns the
   corresponding edge. 

   If the line lies totally outside of the box, returns a 1-by-6 row array
   containing only NaN's.

   If LINE is a N-by-6 array, with one line by row, returns the clipped
   edge coresponding to each line in a N-by-6 array.

   See also:
   lines3d, edges3d, createLine3d, clipRay3d

0001 function edge = clipLine3d(line, box)
0002 %CLIPLINE3D Clip a line with a box and return an edge.
0003 %
0004 %   EDGE = clipLine3d(LINE, BOX);
0005 %   Clips the line LINE with the bounds given in BOX, and returns the
0006 %   corresponding edge.
0007 %
0008 %   If the line lies totally outside of the box, returns a 1-by-6 row array
0009 %   containing only NaN's.
0010 %
0011 %   If LINE is a N-by-6 array, with one line by row, returns the clipped
0012 %   edge coresponding to each line in a N-by-6 array.
0013 %
0014 %   See also:
0015 %   lines3d, edges3d, createLine3d, clipRay3d
0016 %
0017 
0018 % ---------
0019 % author : David Legland
0020 % e-mail: david.legland@inra.fr
0021 % INRA - TPV URPOI - BIA IMASTE
0022 % created the 30/10/2008 from drawLine3d
0023 
0024 %   HISTORY
0025 %   30/10/2008 replace intersectPlaneLine by intersectLinePlane
0026 %   25/11/2008 improve test for bounds, and use more explicit code
0027 %   22/06/2009 fig bug, add support for several lines
0028 %   16/11/2010 use middle point for checking edge bounds
0029 
0030 % get box limits
0031 xmin = box(1); xmax = box(2);
0032 ymin = box(3); ymax = box(4);
0033 zmin = box(5); zmax = box(6);
0034 
0035 % extreme corners of the box
0036 p000 = [xmin ymin zmin];
0037 p111 = [xmax ymax zmax];
0038 
0039 % main vectors
0040 ex   = [1 0 0];
0041 ey   = [0 1 0];
0042 ez   = [0 0 1];
0043 
0044 % box faces parallel to Oxy
0045 planeZ0 = [p000 ex ey];
0046 planeZ1 = [p111 ex ey];
0047 
0048 % box faces parallel to Oxz
0049 planeY0 = [p000 ex ez];
0050 planeY1 = [p111 ex ez];
0051 
0052 % box faces parallel to Oyz
0053 planeX0 = [p000 ey ez];
0054 planeX1 = [p111 ey ez];
0055 
0056 % number of lines
0057 nLines = size(line, 1);
0058 
0059 % allocate memory for result
0060 edge = zeros(nLines, 6);
0061 
0062 % iterate over lines to clip
0063 for i = 1:nLines
0064     
0065     % compute intersection point with each plane
0066     ipZ0 = intersectLinePlane(line(i,:), planeZ0);
0067     ipZ1 = intersectLinePlane(line(i,:), planeZ1);
0068     ipY0 = intersectLinePlane(line(i,:), planeY0);
0069     ipY1 = intersectLinePlane(line(i,:), planeY1);
0070     ipX1 = intersectLinePlane(line(i,:), planeX1);
0071     ipX0 = intersectLinePlane(line(i,:), planeX0);
0072 
0073     % concatenate resulting points
0074     points  = [ipX0;ipX1;ipY0;ipY1;ipZ0;ipZ1];
0075 
0076     % compute position of each point on the line
0077     pos     = linePosition3d(points, line(i,:));
0078 
0079     % keep only defined points
0080     ind     = find(~isnan(pos));
0081     pos     = pos(ind);
0082     points  = points(ind,:);
0083 
0084     % sort points with respect to their position
0085     [pos, ind] = sort(pos); %#ok<ASGLU>
0086     points  = points(ind, :);
0087 
0088     % keep median points wrt to position. These points define the limit of
0089     % the clipped edge.
0090     nv      = length(ind)/2;
0091 
0092     % create resulting edge.
0093     edge(i,:)   = [points(nv, :) points(nv+1, :)];
0094 end
0095 
0096 % check that middle point of the edge is contained in the box
0097 midX = mean(edge(:, [1 4]), 2);
0098 xOk  = xmin <= midX & midX <= xmax;
0099 midY = mean(edge(:, [2 5]), 2);
0100 yOk  = ymin <= midY & midY <= ymax;
0101 midZ = mean(edge(:, [3 6]), 2);
0102 zOk  = zmin <= midZ & midZ <= zmax;
0103 
0104 % if one of the bounding condition is not met, set edge to NaN
0105 edge (~(xOk & yOk & zOk), :) = NaN;
0106