学步园

bool areVecsEqual(b2Vec2 v1, b2Vec2 v2) {
		return v1.x == v2.x && v1.y == v2.y;
	}

bool HelloWorld::linesCross(b2Vec2 v0, b2Vec2 v1, b2Vec2 t0, b2Vec2 t1, b2Vec2 &intersectionPoint)
{
	if ( areVecsEqual(v1,t0) ||
		areVecsEqual(v0,t0) ||
		areVecsEqual(v1,t1) ||
		areVecsEqual(v0,t1) )
		return false;

	b2Vec2 vnormal = v1 - v0;
	vnormal = b2Cross(1.0f, vnormal);
	float v0d = b2Dot(vnormal, v0);
	float t0d = b2Dot(vnormal, t0);
	float t1d = b2Dot(vnormal, t1);
	if ( t0d > v0d && t1d > v0d )
		return false;
	if ( t0d < v0d && t1d < v0d )
		return false;

	b2Vec2 tnormal = t1 - t0;
	tnormal = b2Cross(1.0f, tnormal);
	t0d = b2Dot(tnormal, t0);
	v0d = b2Dot(tnormal, v0);
	float v1d = b2Dot(tnormal, v1);
	if ( v0d > t0d && v1d > t0d )
		return false;
	if ( v0d < t0d && v1d < t0d )
		return false;

	intersectionPoint = v0 + ((t0d-v0d)/(v1d-v0d)) * (v1-v0);

	return true;
}

bool areVecsEqual(b2Vec2 v1, b2Vec2 v2) {
		return v1.x == v2.x && v1.y == v2.y;
	}

bool areVecsEqual(b2Vec2 v1, b2Vec2 v2) {
return v1.x == v2.x && v1.y == v2.y;
}