Polygon LinePolygonIntersection( Polygon poly, float x1, float y1, float x2, float y2 ) {
int size = poly->numberOfVertices, i, k;
float x3, y3, x4, y4, xInt, yInt;
Polygon intersections = NewPolygon(10);
for (i=0;i<size;i++) {
x3 = poly->vertices[i].x;
y3 = poly->vertices[i].y;
k = ( i + 1 ) % size;
x4 = poly->vertices[k].x;
y4 = poly->vertices[k].y;
k = LineLineIntersection( x1, y1, x2, y2, x3, y3, x4, y4, &xInt, &yInt );
switch ( k ) {
case 2: AddPolygonVertex(intersections,x3,y3);
AddPolygonVertex(intersections,x4,y4);
break;
case 1: AddPolygonVertex(intersections,xInt,yInt);
case 0: break;
}
}
return intersections;
}
bool PhysicsSystem::InsideConcaveShape(const Vector3* shapePoints, const int numPoints, const Vector3& testPoint){
int intersectionCount = 0;
//Counting hom many times we cross the line.
for( int i = 0; i < numPoints; ++i){
const int i0 = i;
const int i1 = (i+1)%numPoints;
const Vector3& p0 = shapePoints[i0];
const Vector3& p1 = shapePoints[i1];
bool intersect = LineLineIntersection(Line_c(p0,p1), Line_c(testPoint, testPoint + Vector3(1000,1000,0)));
if (intersect){
intersectionCount++;
}
}
//Even = false;
if(intersectionCount % 2 == 0){
return false;
}
else {return true;}
}