// Tests if two edges defined by their endpoints (a,b) and (c,d) intersect. Returns true and the
// point of intersection if they do and false otherwise.
static bool edgeEdgeTest(const FloatPoint& a, const FloatPoint& b, const FloatPoint& c, const FloatPoint& d, FloatPoint& r)
{
FloatSize u = b - a;
FloatSize v = d - c;
FloatSize w = a - c;
float denom = perpProduct(u, v);
// If denom == 0 then the edges are parallel. While they could be overlapping
// we don't bother to check here as the we'll find their intersections from the
// corner to quad tests.
if (!denom)
return false;
float s = perpProduct(v, w) / denom;
if (s < 0 || s > 1)
return false;
float t = perpProduct(u, w) / denom;
if (t < 0 || t > 1)
return false;
u.scale(s);
r = a + u;
return true;
}
// Tests if two edges defined by their endpoints (a,b) and (c,d) intersect. Returns true and the
// point of intersection if they do and false otherwise.
static bool edgeEdgeTest(const FloatPoint& a, const FloatPoint& b, const FloatPoint& c, const FloatPoint& d, FloatPoint& r)
{
FloatSize u = b - a;
FloatSize v = d - c;
FloatSize w = a - c;
float denom = perpProduct(u, v);
// If denom == 0 then the edges are parallel.
if (!denom) {
// If the edges are not colinear then there's no intersection.
if (perpProduct(u, w) || perpProduct(v, w))
return false;
if (pointInColinearEdge(a, c, d)) {
r = a;
return true;
}
if (pointInColinearEdge(b, c, d)) {
r = b;
return true;
}
if (pointInColinearEdge(c, a, b)) {
r = c;
return true;
}
if (pointInColinearEdge(d, a, b)) {
r = d;
return true;
}
return false;
}
float s = perpProduct(v, w) / denom;
if (s < 0 || s > 1)
return false;
float t = perpProduct(u, w) / denom;
if (t < 0 || t > 1)
return false;
u.scale(s);
r = a + u;
return true;
}
