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//
// libavg - Media Playback Engine.
// Copyright (C) 2003-2014 Ulrich von Zadow
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
// Current versions can be found at www.libavg.de
//
#include "GeomHelper.h"
#include <math.h>
#include <iostream>
using namespace std;
namespace avg {
LineSegment::LineSegment(const glm::vec2& pt0, const glm::vec2& pt1)
: p0(pt0),
p1(pt1)
{
}
bool LineSegment::isPointOver(const glm::vec2& pt)
{
glm::vec2 c = pt - p0;
glm::vec2 v = (p1 - p0);
float d = glm::length(v);
v /= d;
float t = glm::dot(v, c);
return (t >= 0 && t <= d);
}
// Code adapted from Antonio, Franklin, "Faster Line Segment Intersection,"
// Graphics Gems III (David Kirk, ed.), Academic Press, pp. 199-202, 1992.
bool lineSegmentsIntersect(const LineSegment& l0, const LineSegment& l1)
{
float xdiff0 = l0.p1.x-l0.p0.x;
float xdiff1 = l1.p0.x-l1.p1.x;
float x1lo, x1hi;
/* X bound box test*/
if (xdiff0 < 0) {
x1lo=l0.p1.x;
x1hi=l0.p0.x;
} else {
x1hi=l0.p1.x;
x1lo=l0.p0.x;
}
if (xdiff1 > 0) {
if (x1hi < l1.p1.x || l1.p0.x < x1lo) {
return false;
}
} else {
if (x1hi < l1.p0.x || l1.p1.x < x1lo) {
return false;
}
}
float ydiff0 = l0.p1.y-l0.p0.y;
float ydiff1 = l1.p0.y-l1.p1.y;
float y1lo, y1hi;
/* Y bound box test*/
if (ydiff0 < 0) {
y1lo=l0.p1.y;
y1hi=l0.p0.y;
} else {
y1hi=l0.p1.y;
y1lo=l0.p0.y;
}
if (ydiff1 > 0) {
if (y1hi < l1.p1.y || l1.p0.y < y1lo) {
return false;
}
} else {
if (y1hi < l1.p0.y || l1.p1.y < y1lo) {
return false;
}
}
float Cx = l0.p0.x-l1.p0.x;
float Cy = l0.p0.y-l1.p0.y;
float d = ydiff1*Cx - xdiff1*Cy; /* alpha numerator*/
float f = ydiff0*xdiff1 - xdiff0*ydiff1; /* both denominator*/
if (f > 0) { /* alpha tests*/
if (d < 0 || d > f) {
return false;
}
} else {
if (d > 0 || d < f) {
return false;
}
}
float e = xdiff0*Cy - ydiff0*Cx; /* beta numerator*/
if(f > 0) { /* beta tests*/
if (e < 0 || e > f) {
return false;
}
} else {
if (e > 0 || e < f) {
return false;
}
}
if (f == 0) {
// Theoretically, lines could still intersect in this case, but we don't care
// because given numerical inaccuracies, the result is random anyway :-).
return false;
}
// /*compute intersection coordinates*/
// float num = d*xdiff0; /* numerator */
// offset = SAME_SIGNS(num,f) ? f/2 : -f/2; /* round direction*/
// *x = x1 + (num+offset) / f; /* intersection x */
//
// num = d*ydiff0;
// offset = SAME_SIGNS(num,f) ? f/2 : -f/2;
// *y = y1 + (num+offset) / f; /* intersection y */
return true;
}
// Original code from:
// http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html.
// Precomputing a bounding box for the polygon would speed this up a lot,
// but the function hasn't shown up on any profiles so far.
bool pointInPolygon(const glm::vec2& pt, const vector<glm::vec2>& poly)
{
if (poly.size() < 3) {
return false;
}
bool bPtInPoly = false;
for (unsigned i = 0, j = poly.size()-1; i < poly.size(); j = i++) {
if (((poly[i].y > pt.y) != (poly[j].y > pt.y)) &&
(pt.x < (poly[j].x-poly[i].x)*(pt.y-poly[i].y) / (poly[j].y-poly[i].y)
+poly[i].x))
{
bPtInPoly = !bPtInPoly;
}
}
return bPtInPoly;
}
glm::vec2 getLineLineIntersection(const glm::vec2& p1, const glm::vec2& v1,
const glm::vec2& p2, const glm::vec2& v2)
{
float denom = v2.y*v1.x-v2.x*v1.y;
if (fabs(denom) < 0.0000001) {
// If the lines are parallel or coincident, we just return p2!
return p2;
}
float numer = v2.x*(p1.y-p2.y) - v2.y*(p1.x-p2.x);
float ua = numer/denom;
return p1+ua*v1;
}
}
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