Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / geometry-1.5.0 / geom2d / intersectLineCircle.m

diff --git a/octave_packages/geometry-1.5.0/geom2d/intersectLineCircle.m b/octave_packages/geometry-1.5.0/geom2d/intersectLineCircle.m
new file mode 100644 (file)
index 0000000..dde01d0
--- /dev/null
+++ b/octave_packages/geometry-1.5.0/geom2d/intersectLineCircle.m
@@ -0,0 +1,106 @@
+%% Copyright (c) 2011, INRA
+%% 2011, David Legland <david.legland@grignon.inra.fr>
+%% 2011 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
+%%
+%% All rights reserved.
+%% (simplified BSD License)
+%%
+%% Redistribution and use in source and binary forms, with or without
+%% modification, are permitted provided that the following conditions are met:
+%%
+%% 1. Redistributions of source code must retain the above copyright notice, this
+%%    list of conditions and the following disclaimer.
+%%     
+%% 2. Redistributions in binary form must reproduce the above copyright notice, 
+%%    this list of conditions and the following disclaimer in the documentation
+%%    and/or other materials provided with the distribution.
+%%
+%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+%% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+%% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+%% ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+%% LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
+%% CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+%% SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
+%% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+%% CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+%% ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+%% POSSIBILITY OF SUCH DAMAGE.
+%%
+%% The views and conclusions contained in the software and documentation are
+%% those of the authors and should not be interpreted as representing official
+%% policies, either expressed or implied, of copyright holder.
+
+%% -*- texinfo -*-
+%% @deftypefn {Function File} {@var{points} = } intersectLineCircle (@var{line}, @var{circle})
+%% Intersection point(s) of a line and a circle
+%%
+%%   INTERS = intersectLineCircle(LINE, CIRCLE);
+%%   Returns a 2-by-2 array, containing on each row the coordinates of an
+%%   intersection point. If the line and circle do not intersect, the result
+%%   is filled with NaN.
+%%
+%%   Example
+%%   % base point
+%%   center = [10 0];
+%%   % create vertical line
+%%   l1 = [center 0 1];
+%%   % circle
+%%   c1 = [center 5];
+%%   pts = intersectLineCircle(l1, c1)
+%%   pts = 
+%%       10   -5
+%%       10    5
+%%   % draw the result
+%%   figure; clf; hold on;
+%%   axis([0 20 -10 10]);
+%%   drawLine(l1);
+%%   drawCircle(c1);
+%%   drawPoint(pts, 'rx');
+%%   axis equal;
+%%
+%%   @seealso{lines2d, circles2d, intersectLines, intersectCircles}
+%% @end deftypefn
+
+function points = intersectLineCircle(line, circle)
+
+  % local precision
+  eps = 1e-14;
+
+  % center parameters
+  center = circle(:, 1:2);
+  radius = circle(:, 3);
+
+  % line parameters
+  dp = line(:, 1:2) - center;
+  vl = line(:, 3:4);
+
+  % coefficient of second order equation
+  a = sum(line(:, 3:4).^2, 2);
+  b = 2*sum(dp .* vl, 2);
+  c =  sum(dp.^2, 2) - radius.^2;
+
+  % discriminant
+  delta = b .^ 2 - 4 * a .* c;
+
+  if delta > eps
+      % find two roots of second order equation
+      u1 = (-b - sqrt(delta)) / 2 ./ a;
+      u2 = (-b + sqrt(delta)) / 2 ./ a;
+      
+      % convert into 2D coordinate
+      points = [line(1:2) + u1 * line(3:4) ; line(1:2) + u2 * line(3:4)];
+
+  elseif abs(delta) < eps
+      % find unique root, and convert to 2D coord.
+      u = -b / 2 ./ a;    
+      points = line(1:2) + u*line(3:4);
+      
+  else
+      % fill with NaN
+      points = NaN * ones(2, 2);
+      return;
+  end
+
+endfunction
+