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Pt In Poly simple algorithm. Works for convex & concave polygons.
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#include <stdlib.h> // MUST BE BEFORE GLUT ON WINDOWS | |
#ifdef _WIN32 | |
#include <gl/glut.h> | |
#else | |
#include <GLUT/glut.h> | |
#include <OpenGL/gl.h> | |
#include <OpenGL/glu.h> | |
#endif | |
#include <vector> | |
using namespace std; | |
inline float& clamp( float& x, float minVal, float maxVal ) { | |
if( x < minVal ) x = minVal ; | |
else if( x > maxVal ) x = maxVal ; | |
return x ; | |
} | |
struct Vector2f | |
{ | |
float x,y; | |
Vector2f():x(0.f),y(0.f){} | |
Vector2f( float ix, float iy ):x(ix),y(iy){} | |
//Vector2f( const CGPoint& o ):x( o. { } | |
Vector2f( float iv ):x(iv),y(iv){} | |
} ; | |
union Vector4f | |
{ | |
struct{ float x,y,z,w ; } ; | |
struct{ float r,g,b,a ; } ; | |
float elts[4]; | |
Vector4f():x(0.f),y(0.f),z(0.f),w(1.f){} | |
Vector4f( float ix, float iy, float iz ):x(ix),y(iy),z(iz),w(1.f){} | |
Vector4f( float ix, float iy, float iz, float iw ):x(ix),y(iy),z(iz),w(iw){} | |
Vector4f( float iv ):x(iv),y(iv),z(iv),w(iv){} | |
} ; | |
Vector4f Red( 1,0,0,1 ), DarkRed( 0.35,0,0,1 ), | |
Green( 0,1,0,1 ), DarkGreen( 0,0.35,0,1 ), | |
Blue( 0,0,1,1 ), DarkBlue( 0,0,0.35,1 ), | |
White(1,1,1,1), Gray(0.5,0.5,0.65,1), DarkGray(0.21,0.21,0.21,1), Black(0,0,0,1), | |
Magenta(1,0,1,1), Teal(0,1,1,1), Yellow(1,1,0,1), | |
TWhite(1,1,1,0), TBlack(0,0,0,0) | |
; | |
inline bool GL_OK() | |
{ | |
GLenum err = glGetError() ; | |
if( err != GL_NO_ERROR ) | |
printf( "GLERROR %d\n", err ) ; | |
return err == GL_NO_ERROR ; | |
} | |
static float w=512.f,h=512.f,ptSize=1.f ; | |
static Vector2f mousePos ; | |
struct Poly | |
{ | |
vector<Vector2f> pts ; | |
vector<Vector4f> colors ; | |
void setColor( const Vector4f& color ) | |
{ | |
for( int i = 0 ; i < colors.size() ; i++ ) | |
colors[i] = color ; | |
} | |
void draw() | |
{ | |
if( colors.size() != pts.size() ) { | |
printf( "ERROR colors.size( %d ) != pts.size( %d )\n", colors.size(), pts.size() ) ; | |
colors.resize( pts.size() ) ; // shouldn't happen, but could. | |
} | |
//if( !pts.size() ) { | |
// puts( "ERROR NO PTS INSIDE POLYGON" ) ; | |
// return ; | |
//} | |
else if( pts.size() == 1 ) | |
glBegin( GL_POINTS ) ; | |
else if( pts.size() == 2 ) | |
glBegin( GL_LINES ) ; | |
else | |
glBegin( GL_POLYGON ) ; | |
for( int i = 0 ; i < pts.size() ; i++ ) | |
{ | |
glColor4fv( &colors[i].x ) ; | |
glVertex2fv( &pts[i].x ) ; | |
} | |
glEnd() ; | |
} | |
void addPt( const Vector2f &pt, const Vector4f &color ) | |
{ | |
pts.push_back( pt ) ; | |
colors.push_back( color ) ; | |
} | |
int pnpoly( const Vector2f& test ) | |
{ | |
int i, j, c = 0; | |
for (i = 0, j = pts.size()-1; i < pts.size(); j = i++) { | |
if ( ((pts[i].y>test.y) != (pts[j].y>test.y)) && | |
(test.x < (pts[j].x-pts[i].x) * (test.y-pts[i].y) / (pts[j].y-pts[i].y) + pts[i].x) ) | |
c = !c; | |
} | |
return c; | |
} | |
} ; | |
vector<Poly*> polys; | |
static Poly* cp = 0; | |
void addPt( const Vector2f& pt ) | |
{ | |
cp->addPt( pt, White ) ; | |
} | |
void draw() | |
{ | |
glEnable( GL_DEPTH_TEST ) ; | |
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) ; | |
glViewport( 0, 0, w, h ) ; | |
glMatrixMode( GL_PROJECTION ) ; | |
glLoadIdentity(); | |
glOrtho( 0, w, 0, h, 10, -10 ) ; | |
glMatrixMode(GL_MODELVIEW); | |
glLoadIdentity(); | |
for( Poly * p : polys ) p->draw() ; | |
glBegin( GL_POINTS ) ; | |
glColor4f( 1,1,0,1 ) ; | |
glVertex2fv( &mousePos.x ) ; | |
glEnd() ; | |
//TEXT | |
glDisable( GL_DEPTH_TEST ) ; | |
glColor4f(1.0f, 1.0f, 1.0f, 1.0f); | |
glRasterPos2f( 20, h-20 ) ; | |
char buf[300]; | |
if( !polys.size() ) | |
sprintf( buf, "Left click: add pt." ) ; | |
else | |
sprintf( buf, "Move mouse to poly test. Keys: new (p)oly, (c)lear all polys." ) ; | |
const char * p = buf ; | |
do glutBitmapCharacter( GLUT_BITMAP_HELVETICA_18, *p ); while( *(++p) ) ; | |
glutSwapBuffers(); | |
} | |
// Called every time a window is resized to resize the projection matrix | |
void resize( int newWidth, int newHeight ) | |
{ | |
w = newWidth ; | |
h = newHeight ; | |
} | |
void newPoly() | |
{ | |
polys.push_back( new Poly() ) ; | |
cp = polys.back() ; | |
} | |
void mouse( int button, int up, int x, int y ) | |
{ | |
if( !cp ) newPoly() ; | |
y = h-y; | |
if( !up ) | |
addPt( Vector2f( x, y ) ) ; | |
} | |
void mouseMotion( int x, int y ) | |
{ | |
Vector2f pt( x, h-y ) ; | |
mousePos = pt ; | |
for( int i = 0 ; i < polys.size() ; i++ ) | |
{ | |
if( polys[i]->pnpoly( pt ) ) | |
{ | |
polys[i]->setColor( Red ) ; | |
} | |
else | |
{ | |
polys[i]->setColor( White ) ; | |
} | |
} | |
} | |
void keyboard( unsigned char key, int x, int y ) | |
{ | |
static float lineWidth = 1.f ; | |
switch( key ) | |
{ | |
case '2': | |
{ | |
int pMode[2]; | |
glGetIntegerv( GL_POLYGON_MODE, pMode ) ; | |
if( pMode[0] == GL_FILL ) glPolygonMode( GL_FRONT_AND_BACK, GL_LINE ) ; | |
else glPolygonMode( GL_FRONT_AND_BACK, GL_FILL ) ; | |
} | |
break ; | |
case '-': | |
lineWidth--; | |
::clamp( lineWidth, 1.f, 16.f ) ; | |
glLineWidth( lineWidth ) ; | |
break; | |
case '+': | |
case '=': | |
lineWidth++; | |
::clamp( lineWidth, 1.f, 16.f ) ; | |
glLineWidth( lineWidth ) ; | |
break; | |
case 'c': | |
puts( "Clear" ) ; | |
for( Poly * p : polys ) delete p ; | |
cp=0; | |
polys.clear() ; | |
break ; | |
case 'p': | |
newPoly() ; | |
break ; | |
case 27: | |
exit(0); | |
break; | |
default: | |
break; | |
} | |
} | |
void init() | |
{ | |
glClearColor( 0.1, 0.1, 0.1, 0.1 ) ; | |
glEnable( GL_COLOR_MATERIAL ) ; | |
ptSize=4.f; | |
glPointSize( ptSize ) ; | |
glLineWidth( 2.f ) ; | |
glPolygonMode( GL_FRONT_AND_BACK, GL_LINE ) ; | |
glEnable( GL_BLEND ) ; | |
glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ; | |
} | |
int main( int argc, char **argv ) | |
{ | |
glutInit( &argc, argv ) ; // Initializes glut | |
glutInitDisplayMode( GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA ) ; | |
glutInitWindowSize( w, h ) ; | |
glutInitWindowPosition( 0, 0 ) ; | |
glutCreateWindow( "Point in poly" ) ; | |
glutReshapeFunc( resize ) ; | |
glutDisplayFunc( draw ) ; | |
glutIdleFunc( draw ) ; | |
glutMouseFunc( mouse ) ; | |
glutPassiveMotionFunc( mouseMotion ) ; | |
glutKeyboardFunc( keyboard ) ; | |
init(); | |
glutMainLoop(); | |
return 0; | |
} | |
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From http://stackoverflow.com/a/2922778/111307