private static Boolean RectCirc(CollisionRectangle rectangle, CollisionCircle circle)
{
// Transform rectangle corner coordinates and circle center to be axis-aligned
Matrix rotationMatrix = new Matrix();
rotationMatrix.Set2DRotate(-1 * rectangle.Rotation);
Vector rotatedTopLeft = rectangle.TopLeft * rotationMatrix;
Vector rotatedTopRight = rectangle.TopRight * rotationMatrix;
Vector rotatedBottomLeft = rectangle.BottomLeft * rotationMatrix;
Vector rotatedBottomRight = rectangle.BottomRight * rotationMatrix;
Vector rotatedCircleCenter = circle.Center * rotationMatrix;
double circRadius = circle.Radius;
Vector rotatedRectangleCenter = rotatedTopLeft + (rotatedBottomRight - rotatedTopLeft).Multiply(0.5);
double rectPercent = rectangle.CollisionPercent;
// Use of doubles and matrix operations can cause very very small discrepencies that should be ignored
if (Math.Abs(rotatedTopLeft.Y - rotatedTopRight.Y) > 0.00000001)
{
throw new Exception("Coordinate transform failed in CollisionDetector.RectCirc. TopLeft is " + rotatedTopLeft + " and TopRight is "+ rotatedTopRight);
}
bool isCircCenterOutsideRect = true;
double rectHalfWidth = 0.5 * Math.Abs(rotatedTopRight.X - rotatedTopLeft.X) * rectPercent;
double halfWidthPlusRadius = rectHalfWidth + circRadius;
double xSeparation = Math.Abs(rotatedCircleCenter.X - rotatedRectangleCenter.X);
if (xSeparation >= halfWidthPlusRadius) { return false; }
if (xSeparation < rectHalfWidth) { isCircCenterOutsideRect = false; }
double rectHalfHeight = 0.5 * Math.Abs(rotatedTopRight.Y - rotatedBottomRight.Y) * rectPercent;
double halfHeightPlusRadius = rectHalfWidth + circRadius;
double ySeparation = Math.Abs(rotatedCircleCenter.Y - rotatedRectangleCenter.Y);
if (ySeparation >= halfHeightPlusRadius) { return false; }
if (ySeparation < rectHalfHeight) { isCircCenterOutsideRect = false; }
if (!isCircCenterOutsideRect) { return true; }
// Check for literal corner cases
Vector closestCorner;
if (rotatedCircleCenter.X > rotatedRectangleCenter.X && rotatedCircleCenter.Y > rotatedRectangleCenter.Y) { closestCorner = rotatedTopRight; }
else if (rotatedCircleCenter.X > rotatedRectangleCenter.X && rotatedCircleCenter.Y <= rotatedRectangleCenter.Y) { closestCorner = rotatedBottomRight; }
else if (rotatedCircleCenter.Y > rotatedRectangleCenter.Y) { closestCorner = rotatedTopLeft; }
else { closestCorner = rotatedBottomLeft; }
if ((closestCorner - rotatedCircleCenter).LengthSquared > circRadius * circRadius) { return false; }
return true;
}
private static bool IsSeparatingAxis(Vector sepAxisPoint1, Vector sepAxisPoint2, Vector thirdPoint, CollisionRectangle otherRectangle)
{
Vector[] otherQuadPoints = new Vector[4];
otherQuadPoints[0] = otherRectangle.TopLeft;
otherQuadPoints[1] = otherRectangle.TopRight;
otherQuadPoints[2] = otherRectangle.BottomLeft;
otherQuadPoints[3] = otherRectangle.BottomRight;
Vector separatingAxis = sepAxisPoint2 - sepAxisPoint1;
Vector normalAxis = new Vector(separatingAxis.Y, -separatingAxis.X);
bool referenceSign = normalAxis * (thirdPoint - sepAxisPoint1) >= 0;
foreach (Vector cornerOfSecondRect in otherQuadPoints)
{
bool sign = normalAxis * (cornerOfSecondRect - sepAxisPoint1) >= 0;
// A point of the other quad is one the same side as thirdPoint
if (sign == referenceSign) { return false; }
}
// All points of the other quad are on the other side of the edge. Therefore the edge is a separating axis
return true;
}
private static Boolean RectRect(CollisionRectangle rect1, CollisionRectangle rect2)
{
double rect1Radius = (rect1.TopLeft - rect1.Center).Length;
double rect2Radius = (rect2.TopLeft - rect2.Center).Length;
double distanceBetweenCenters = (rect1.Center - rect2.Center).Length;
if (distanceBetweenCenters >= rect1Radius + rect2Radius) { return false; }
if (IsSeparatingAxis(rect1.TopLeft, rect1.TopRight, rect1.BottomRight, rect2)) { return false; }
if (IsSeparatingAxis(rect1.TopRight, rect1.BottomRight, rect1.BottomLeft, rect2)) { return false; }
if (IsSeparatingAxis(rect1.BottomRight, rect1.BottomLeft, rect1.TopLeft, rect2)) { return false; }
if (IsSeparatingAxis(rect1.BottomLeft, rect1.TopLeft, rect1.TopRight, rect2)) { return false; }
if (IsSeparatingAxis(rect2.TopLeft, rect2.TopRight, rect2.BottomRight, rect1)) { return false; }
if (IsSeparatingAxis(rect2.TopRight, rect2.BottomRight, rect2.BottomLeft, rect1)) { return false; }
if (IsSeparatingAxis(rect2.BottomRight, rect2.BottomLeft, rect2.TopLeft, rect1)) { return false; }
if (IsSeparatingAxis(rect2.BottomLeft, rect2.TopLeft, rect2.TopRight, rect1)) { return false; }
return true;
}
