104 lines
2.6 KiB
C++
104 lines
2.6 KiB
C++
// This file is part of libigl, a simple c++ geometry processing library.
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//
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// Copyright (C) 2013 Alec Jacobson <alecjacobson@gmail.com>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public License
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// v. 2.0. If a copy of the MPL was not distributed with this file, You can
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// obtain one at http://mozilla.org/MPL/2.0/.
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#include "line_segment_in_rectangle.h"
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IGL_INLINE bool igl::line_segment_in_rectangle(
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const Eigen::Vector2d & s,
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const Eigen::Vector2d & d,
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const Eigen::Vector2d & A,
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const Eigen::Vector2d & B)
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{
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using namespace std;
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using namespace Eigen;
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// http://stackoverflow.com/a/100165/148668
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const auto SegmentIntersectRectangle = [](double a_rectangleMinX,
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double a_rectangleMinY,
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double a_rectangleMaxX,
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double a_rectangleMaxY,
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double a_p1x,
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double a_p1y,
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double a_p2x,
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double a_p2y)->bool
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{
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// Find min and max X for the segment
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double minX = a_p1x;
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double maxX = a_p2x;
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if(a_p1x > a_p2x)
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{
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minX = a_p2x;
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maxX = a_p1x;
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}
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// Find the intersection of the segment's and rectangle's x-projections
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if(maxX > a_rectangleMaxX)
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{
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maxX = a_rectangleMaxX;
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}
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if(minX < a_rectangleMinX)
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{
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minX = a_rectangleMinX;
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}
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if(minX > maxX) // If their projections do not intersect return false
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{
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return false;
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}
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// Find corresponding min and max Y for min and max X we found before
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double minY = a_p1y;
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double maxY = a_p2y;
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double dx = a_p2x - a_p1x;
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if(fabs(dx) > 0.0000001)
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{
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double a = (a_p2y - a_p1y) / dx;
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double b = a_p1y - a * a_p1x;
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minY = a * minX + b;
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maxY = a * maxX + b;
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}
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if(minY > maxY)
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{
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double tmp = maxY;
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maxY = minY;
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minY = tmp;
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}
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// Find the intersection of the segment's and rectangle's y-projections
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if(maxY > a_rectangleMaxY)
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{
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maxY = a_rectangleMaxY;
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}
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if(minY < a_rectangleMinY)
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{
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minY = a_rectangleMinY;
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}
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if(minY > maxY) // If Y-projections do not intersect return false
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{
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return false;
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}
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return true;
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};
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const double minX = std::min(A(0),B(0));
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const double minY = std::min(A(1),B(1));
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const double maxX = std::max(A(0),B(0));
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const double maxY = std::max(A(1),B(1));
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bool ret = SegmentIntersectRectangle(minX,minY,maxX,maxY,s(0),s(1),d(0),d(1));
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return ret;
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}
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