when use boolean operations on shape, found that on simple examples all work well, but sometime take false on function l Segment2D::findIntersect when it need to be true.
Cannot understand why function is so heavy, change to more simple variant and all works well.
old code
bool Segment2D::findIntersect(const Segment2D& other, Vector2& intersection) const
{
const Vector2& p1 = mA;
const Vector2& p2 = mB;
const Vector2& p3 = other.mA;
const Vector2& p4 = other.mB;
Vector2 d1 = p2-p1;
float a1 = d1.y;
float b1 = -d1.x;
float g1 = d1.x*p1.y-d1.y*p1.x;
Vector2 d3 = p4-p3;
float a2 = d3.y;
float b2 = -d3.x;
float g2 = d3.x*p3.y-d3.y*p3.x;
float det=d1.crossProduct(d3);
// if both segments are parallel, early out
if (det == 0.)
return false;
Vector2 intersect;
float intersectx = (b2*g1-b1*g2)/(b1*a2-b2*a1);
float intersecty = (a2*g1-a1*g2)/(a1*b2-a2*b1);
intersect = Vector2(intersectx, intersecty);
if ((intersect-p1).dotProduct(intersect-p2)<0 && (intersect-p3).dotProduct(intersect-p4)<0)
{
intersection = intersect;
return true;
}
return false;
}
new code
bool Segment2D::findIntersect(const Segment2D& other, Vector2& intersection) const
{
const Vector2& p0 = mA;
const Vector2& p1 = mB;
const Vector2& p2 = other.mA;
const Vector2& p3 = other.mB;
float s1_x, s1_y, s2_x, s2_y;
s1_x = p1.x - p0.x; s1_y = p1.y - p0.y;
s2_x = p3.x - p2.x; s2_y = p3.y - p2.y;
float s, t;
s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
t = ( s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
if (s >= 0 && s <= 1 && t >= 0 && t <= 1)
{
// Collision detected
intersection.x = p0.x + (t * s1_x);
intersection.y = p0.y + (t * s1_y);
return true;
}
return false; // No collision
}
when use boolean operations on shape, found that on simple examples all work well, but sometime take false on function l Segment2D::findIntersect when it need to be true.
Cannot understand why function is so heavy, change to more simple variant and all works well.
old code
new code