/// <summary> /// Determines if a collision has occurred on an Axis of one of the /// planes parallel to the Rectangle /// </summary> /// <param name="theRectangle">The rectangle.</param> /// <param name="aAxis">A axis.</param> /// <returns> /// <c>true</c> if [is axis collision] [the specified the rectangle]; otherwise, <c>false</c>. /// </returns> private bool IsAxisCollision(RotatedRectangle theRectangle, Vector2 aAxis) { //Project the corners of the Rectangle we are checking on to the Axis and //get a scalar value of that project we can then use for comparison List<int> aRectangleAScalars = new List<int>(); aRectangleAScalars.Add(GenerateScalar(theRectangle.UpperLeftCorner(), aAxis)); aRectangleAScalars.Add(GenerateScalar(theRectangle.UpperRightCorner(), aAxis)); aRectangleAScalars.Add(GenerateScalar(theRectangle.LowerLeftCorner(), aAxis)); aRectangleAScalars.Add(GenerateScalar(theRectangle.LowerRightCorner(), aAxis)); //Project the corners of the current Rectangle on to the Axis and //get a scalar value of that project we can then use for comparison List<int> aRectangleBScalars = new List<int>(); aRectangleBScalars.Add(GenerateScalar(UpperLeftCorner(), aAxis)); aRectangleBScalars.Add(GenerateScalar(UpperRightCorner(), aAxis)); aRectangleBScalars.Add(GenerateScalar(LowerLeftCorner(), aAxis)); aRectangleBScalars.Add(GenerateScalar(LowerRightCorner(), aAxis)); //Get the Maximum and Minium Scalar values for each of the Rectangles int aRectangleAMinimum = aRectangleAScalars.Min(); int aRectangleAMaximum = aRectangleAScalars.Max(); int aRectangleBMinimum = aRectangleBScalars.Min(); int aRectangleBMaximum = aRectangleBScalars.Max(); //If we have overlaps between the Rectangles (i.e. Min of B is less than Max of A) //then we are detecting a collision between the rectangles on this Axis if (aRectangleBMinimum <= aRectangleAMaximum && aRectangleBMaximum >= aRectangleAMaximum) { return true; } else if (aRectangleAMinimum <= aRectangleBMaximum && aRectangleAMaximum >= aRectangleBMaximum) { return true; } return false; }
/// <summary> /// Check to see if two Rotated Rectangls have collided /// </summary> /// <param name="theRectangle">The rectangle.</param> /// <returns></returns> public bool Intersects(RotatedRectangle theRectangle) { //Calculate the Axis we will use to determine if a collision has occurred //Since the objects are rectangles, we only have to generate 4 Axis (2 for //each rectangle) since we know the other 2 on a rectangle are parallel. List<Vector2> aRectangleAxis = new List<Vector2>(); aRectangleAxis.Add(UpperRightCorner() - UpperLeftCorner()); aRectangleAxis.Add(UpperRightCorner() - LowerRightCorner()); aRectangleAxis.Add(theRectangle.UpperLeftCorner() - theRectangle.LowerLeftCorner()); aRectangleAxis.Add(theRectangle.UpperLeftCorner() - theRectangle.UpperRightCorner()); //Cycle through all of the Axis we need to check. If a collision does not occur //on ALL of the Axis, then a collision is NOT occurring. We can then exit out //immediately and notify the calling function that no collision was detected. If //a collision DOES occur on ALL of the Axis, then there is a collision occurring //between the rotated rectangles. We know this to be true by the Seperating Axis Theorem foreach (Vector2 aAxis in aRectangleAxis) { if (!IsAxisCollision(theRectangle, aAxis)) { return false; } } return true; }