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example2.cpp
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example2.cpp
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/**
* A simple program experimenting the point in polygon algorithm using C++ and OpenGL.
* example2.cpp supports multiple polygons.
* To run: ./Example2
*
* 1. Draw each polygon by clicking points inside the window,
* it will connect all the consecutive points as line segments.
* 2. Press 'c' to close the polygon (i.e., finishing drawing the current polygon);
* You can start drawing another poygon using the same way in 1.
* 3. Press 'd' if you are done drawing all the polygons,
* a blue point will appear and it will follow your cursor, or you can control the point using keyboard i,k,j,l.
* If the point is in any of the polygons, that polygon will turn red, otherwise they are black。
* 4. Press 'x' to clear the polygons and restart.
*
* Created by Zebin Xu on 9/27/2017
*/
#include <iostream>
#include <vector>
#include "polygon.h"
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
int width = 600;
int height = 600;
Point2d thepoint(width / 2, height / 2);
std::vector<Point2d> points;// a list of points of the polygon in order.
bool drawn = false;//flag indicating if all drawing are done in order to start detection
Polygon* polygon = NULL;
std::vector<Polygon*> polygons;//supporting drawing multiple polygons
void draw_polygon(Polygon& polygon) {
glBegin(GL_LINE_STRIP);
for (auto &point : polygon.points) {
glVertex2i(point.x, point.y);
}
glEnd();
}
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
//draw the polygon
glBegin(GL_LINE_STRIP);
for (auto &polygon : polygons) {
if (drawn && polygon->inPolygon(thepoint)) {
glColor3f(1.0, 0.0, 0.0);
} else {
glColor3f(0.0, 0.0, 0.0);
}
draw_polygon(*polygon);
}
glEnd();
//render the current drawing polygon (unclosed)
glColor3f(0.0, 0.0, 0.0);
glBegin(GL_LINE_STRIP);
for (auto &point : points) {
glVertex2i(point.x, point.y);
}
glEnd();
//draw the point
if (drawn) {
glPointSize(4.0);
glColor3f(0.0, 0.0, 1.0);
glBegin(GL_POINTS);
glVertex2i(thepoint.x, thepoint.y);
glEnd();
}
glFlush();
glutSwapBuffers();
}
void my_init()
{
glClearColor(1.0, 1.0, 1.0, 1.0);
glEnable(GL_LINE_SMOOTH);
}
void reshape(int w, int h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, (GLdouble) w, 0.0, (GLdouble) h);
}
void idle(void)
{
glutPostRedisplay();
}
void keyboard(unsigned char key, int x, int y) {
switch (key) {
case 'q':
case 'Q':
exit(0);
break;
case 'i':
case 'I':
thepoint.y += 5;
break;
case 'k':
case 'K':
thepoint.y -= 5;
break;
case 'j':
case 'J':
thepoint.x -= 5;
break;
case 'l':
case 'L':
thepoint.x += 5;
break;
case 'd':
case 'D':
//finish all the drawings (and may close the final polygon is it is not closed yet)
//and start the point in polygons detection
if (!drawn) {
drawn = true;
//if not closed, add a final point, same as the starting point, to close the polygon
if (points.size() != 0) {
points.push_back(Point2d(points[0]));
}
polygons.push_back(new Polygon(points));
points.clear();
}
break;
case 'c':
case 'C':
//Close the current polygon and start drawing a new polygon
points.push_back(Point2d(points[0]));
polygons.push_back(new Polygon(points));
points.clear();
break;
case 'x':
case 'X':
//Clear all the polygon(s)
polygons.clear();
drawn = false;
default:
break;
}
}
void passiveMotion(int x, int y) {
if (x >= 0 && y >= 0 && x <= width && y <= height) {
thepoint.x = x;
thepoint.y = height - y;
}
}
void mouse(int button, int state, int x, int y) {
if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
if (!drawn) {
points.push_back(Point2d(x, height - y));
}
}
}
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(width, height);
glutInitWindowPosition(100, 100);
glutCreateWindow("Point in Polygons");
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutPassiveMotionFunc(passiveMotion);
glutMouseFunc(mouse);
glutKeyboardFunc(keyboard);
glutIdleFunc(idle);
my_init();
glutMainLoop();
return 0;
}