private bool CircleLineIntersect(MovingObject o, SimpleCollidableLine boundry)
{
Vector2 A = boundry.From;
Vector2 B = boundry.To;
Vector2 C = o.Position;
float r = (o.Width - 5) / 2; // approx. radius of bibble
// compute the euclidean distance between A and B
float lab = Vector2.Distance(A, B);
// compute the direction vector D from A to B
Vector2 D = new Vector2((B.X - A.X) / lab, (B.Y - A.Y) / lab);
// check, whether the centre of o has passed the line within one update cycle
// the object must be fast, else, in the last collision check(s) it would have
// touched the line!
if (Vector2.Distance(o.LastPos, o.Position) > r) // this object is fast!
{
Vector2 C2 = o.LastPos;
float ua = (C.X - C2.X) * (A.Y - C2.Y) - (C.Y - C2.Y) * (A.X - C2.X);
float ub = (B.X - A.X) * (A.Y - C2.Y) - (B.Y - A.Y) * (A.X - C2.X);
float denominator = (C.Y - C2.Y) * (B.X - A.X) - (C.X - C2.X) * (B.Y - A.Y);
if (Math.Abs(denominator) <= 0.00001f)
{
if (Math.Abs(ua) <= 0.00001f && Math.Abs(ub) <= 0.00001f && o.Collide(boundry))
{
//arbitrary intersectionpoint
// (A + B) / 2;
return true;
}
}
else
{
ua /= denominator;
ub /= denominator;
if (ua >= 0 && ua <= 1 && ub >= 0 && ub <= 1)
{
// crossing point E
Vector2 Es = new Vector2(A.X + ua * (B.X - A.X), A.Y + ua * (B.Y - A.Y));
// compute the euclidean distance from E to C
float lecs = (float)Math.Sqrt((Es.X - C.X) * (Es.X - C.X) + (Es.Y - C.Y) * (Es.Y - C.Y));
//intersectionPoint.X = A.X + ua * (B.X - A.X);
//intersectionPoint.Y = A.Y + ua * (B.Y - A.Y);
if (o.Collide(boundry))
{
o.Position = Es;
return true;
}
else
{
//position and orientation correction
Vector2 resulting;
Vector2 oldDirection = new Vector2((float)Math.Cos(o.MovementDirection), (float)Math.Sin(o.MovementDirection));
Vector2 normal = new Vector2(-D.Y, D.X);
Vector2.Reflect(ref oldDirection, ref normal, out resulting);
if (resulting.Length() != 1f)
{
resulting.Normalize();
}
o.MovementDirection = (float)Math.Atan2(resulting.Y, resulting.X);
// move it back distance r-lec and furth r-lec again (in the new direction)
o.Position = Es + resulting * lecs;
return false;
}
}
}
}
if (Vector2.Distance(A, C) + Vector2.Distance(B, C) - 2 * r > lab)
{
return false;
}
// Now the line equation is x = Dx*t + Ax, y = Dy*t + Ay with 0 <= t <= 1.
// compute the value t of the closest point to the circle center (Cx, Cy)
float t = D.X * (C.X - A.X) + D.Y * (C.Y - A.Y);
// This is the projection of C on the line from A to B.
// compute the coordinates of the point E on line and closest to C
Vector2 E = new Vector2(t * D.X + A.X, t * D.Y + A.Y);
// compute the euclidean distance from E to C
float lec = (float)Math.Sqrt((E.X - C.X) * (E.X - C.X) + (E.Y - C.Y) * (E.Y - C.Y));
// test if the line intersects or tangents the circle
if (lec < r) // TODO lec = r
{
/* // compute distance from t to circle intersection point
float dt = (float)Math.Sqrt(r * r - lec * lec);
// compute first intersection point
Vector2 F = new Vector2((t - dt) * D.X + A.X, (t - dt) * D.Y + A.Y);
// compute second intersection point
Vector2 G = new Vector2((t + dt) * D.X + A.X, (t + dt) * D.Y + A.Y);*/
if (o.Collide(boundry))
{
Explosion(E, 0.05f, false); // ugly style
return true;
}
else
{
Vector2 resulting;
Vector2 oldDirection = new Vector2((float)Math.Cos(o.MovementDirection), (float)Math.Sin(o.MovementDirection));
if (Vector2.Distance(C - oldDirection, E) < Vector2.Distance(C + oldDirection, E)) return false;
Vector2 normal = new Vector2(-D.Y, D.X);
Vector2.Reflect(ref oldDirection, ref normal, out resulting);
if (resulting.Length() != 1f)
{
resulting.Normalize();
}
o.MovementDirection = (float)Math.Atan2(resulting.Y, resulting.X);
// move it back distance r-lec and furth r-lec again (in the new direction)
o.Position -= oldDirection * (r - lec);
o.Position += resulting * (r - lec);
return false;
}
}
else
{
// line doesn't touch circle
return false;
}
}
internal void addLine(SimpleCollidableLine l)
{
lines.Add(l);
Components.Add(l);
}
