// Globals which should be set before calling this function: // // int polySides = how many corners the polygon has // float polyX[] = horizontal coordinates of corners // float polyY[] = vertical coordinates of corners // float x, y = point to be tested // // (Globals are used in this example for purposes of speed. Change as // desired.) // // The function will return YES if the point x,y is inside the polygon, or // NO if it is not. If the point is exactly on the edge of the polygon, // then the function may return YES or NO. // // Note that division by zero is avoided because the division is protected // by the "if" clause which surrounds it.
bool pointInPolygon() {
int i, j=polySides-1 ; boolean oddNodes=NO ;
for (i=0; i<polySides; i++) { if (polyY[i]<y && polyY[j]>=y || polyY[j]<y && polyY[i]>=y) { if (polyX[i]+(y-polyY[i])/(polyY[j]-polyY[i])*(polyX[j]-polyX[i])<x) { oddNodes=!oddNodes; }} j=i; }