File: intersectLinePlane.m

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## Copyright (C) 2024 David Legland
## All rights reserved.
## 
## 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 AUTHOR 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 the copyright holders.

function point = intersectLinePlane(line, plane, varargin)
%INTERSECTLINEPLANE Intersection point between a 3D line and a plane.
%
%   PT = intersectLinePlane(LINE, PLANE)
%   Returns the intersection point of the given line and the given plane.
%   LINE:  [x0 y0 z0 dx dy dz]
%   PLANE: [x0 y0 z0 dx1 dy1 dz1 dx2 dy2 dz2]
%   PT:    [xi yi zi]
%   If LINE and PLANE are parallel, return [NaN NaN NaN].
%   If LINE (or PLANE) is a matrix with 6 (or 9) columns and N rows, result
%   is an array of points with N rows and 3 columns.
%   
%   PT = intersectLinePlane(LINE, PLANE, TOL)
%   Specifies the tolerance factor to test if a line is parallel to a
%   plane. Default is 1e-14.
%
%   Example
%     % define horizontal plane through origin
%     plane = [0 0 0   1 0 0   0 1 0];
%     % intersection with a vertical line
%     line = [2 3 4  0 0 1];
%     intersectLinePlane(line, plane)
%     ans = 
%        2   3   0
%     % intersection with a line "parallel" to plane
%     line = [2 3 4  1 2 0];
%     intersectLinePlane(line, plane)
%     ans = 
%       NaN  NaN  NaN
%
%   See also 
%   lines3d, planes3d, points3d, clipLine3d
%

% ------
% Author: David Legland 
% E-mail: david.legland@inrae.fr
% Created: 2005-02-17
% Copyright 2005-2023 INRA - TPV URPOI - BIA IMASTE

% extract tolerance if needed
tol = 1e-14;
if nargin > 2
    tol = varargin{1};
end

% unify sizes of data
nLines  = size(line, 1);
nPlanes = size(plane, 1);

% N planes and M lines not allowed 
if nLines ~= nPlanes && min(nLines, nPlanes) > 1
    error('MatGeom:geom3d:intersectLinePlane', ...
        'Input must have same number of rows, or one must be 1');
end

% plane normal
n = crossProduct3d(plane(:,4:6), plane(:,7:9));

% difference between origins of plane and line
dp = bsxfun(@minus, plane(:, 1:3), line(:, 1:3));

% dot product of line direction with plane normal
denom = sum(bsxfun(@times, n, line(:,4:6)), 2);

% relative position of intersection point on line (can be inf in case of a
% line parallel to the plane)
t = sum(bsxfun(@times, n, dp),2) ./ denom;

% compute coord of intersection point
point = bsxfun(@plus, line(:,1:3),  bsxfun(@times, [t t t], line(:,4:6)));

% set indices of line and plane which are parallel to NaN
par = abs(denom) < tol;
point(par,:) = NaN;