public Fuzzy MoveAlong(Direction direction, double step, out Position newPosition)
{
// simple case #1 : dx == 0
if ( direction.Dx == 0 )
{
newPosition = new Position(x, y + step * Fuzzy.Sign(direction.Dy));
return step;
}
// simple case #2 : dy == 0
if ( direction.Dy == 0)
{
newPosition = new Position(x + step * Fuzzy.Sign(direction.Dx), y);
return step;
}
var newXOnGrid = GetNextPositionOnGrid(x, direction.Dx, step);
var newYOnGrid = GetNextPositionOnGrid(y, direction.Dy, step);
var xMotion = newXOnGrid - x;
var yMotion = newYOnGrid - y;
Debug.Assert(Fuzzy.Abs(xMotion) > 0);
Debug.Assert(Fuzzy.Abs(xMotion) <= 0.5);
Debug.Assert(Fuzzy.Abs(yMotion) > 0);
Debug.Assert(Fuzzy.Abs(yMotion) <= 0.5);
// shorter motion on X axis
if (xMotion / direction.Dx < yMotion / direction.Dy)
{
yMotion = xMotion * direction.Dy / direction.Dx;
Debug.Assert(Fuzzy.Abs(yMotion) > 0);
Debug.Assert(Fuzzy.Abs(yMotion) <= 0.5);
}
// shorter motion on Y axis
else if (xMotion / direction.Dx > yMotion / direction.Dy)
{
xMotion = yMotion * direction.Dx / direction.Dy;
Debug.Assert(Fuzzy.Abs(xMotion) > 0);
Debug.Assert(Fuzzy.Abs(xMotion) <= 0.5);
}
Debug.Assert(yMotion / xMotion == direction.Dy / direction.Dx);
newPosition = new Position(x + xMotion, y + yMotion);
return Fuzzy.Sqrt(xMotion * xMotion + yMotion * yMotion);
}
public bool SolveDirection(Direction direction)
{
var distance = new Fuzzy(0.0);
var position = startPosition;
Log("----");
while (true)
{
Log("(X ; Y) = ({0} ; {1})", position.X, position.Y);
Log("(dX ; dY) = ({0} ; {1})", direction.Dx, direction.Dy);
distance += position.MoveAlong(direction, step, out position);
if (distance > maxDistance)
{
Log("Max distance reached");
return false;
}
if (position.Equals(startPosition))
{
Log("Start position reached !!!");
return true;
}
bool reflectionOnX, reflectionOnY;
var xOnGrid = Fuzzy.Floor(position.X);
var yOnGrid = Fuzzy.Floor(position.Y);
Log("(X ; Y) = ({0} ; {1})", position.X, position.Y);
var isOnHorizontalGrid = position.Y == yOnGrid;
var isOnVerticalGrid = position.X == xOnGrid;
Log("isOnHorizontalGrid = {0}", isOnHorizontalGrid);
Log("isOnVerticalGrid = {0}", isOnVerticalGrid);
if (isOnHorizontalGrid && isOnVerticalGrid)
{
var mirrorOnUpperLeft = IsMirrorAt(position.X - step, position.Y - step);
var mirrorOnUpperRight = IsMirrorAt(position.X + step, position.Y - step);
var mirrorOnLowerLeft = IsMirrorAt(position.X - step, position.Y + step);
var mirrorOnLowerRight = IsMirrorAt(position.X + step, position.Y + step);
// we can't possibly be in the middle of 4 mirrors
Debug.Assert(!(mirrorOnUpperLeft&&mirrorOnUpperRight&&mirrorOnLowerLeft&&mirrorOnLowerRight));
reflectionOnX =
mirrorOnUpperLeft && mirrorOnLowerLeft ||
mirrorOnUpperRight && mirrorOnLowerRight;
reflectionOnY =
mirrorOnUpperLeft && mirrorOnUpperRight ||
mirrorOnLowerLeft && mirrorOnLowerRight;
}
else if (isOnHorizontalGrid)
{
var mirrorAbove = IsMirrorAt(position.X, position.Y - step);
var mirrorBelow = IsMirrorAt(position.X, position.Y + step);
reflectionOnY = mirrorAbove || mirrorBelow;
reflectionOnX = false;
}
else if (isOnVerticalGrid)
{
var mirrorOnLeft = IsMirrorAt(position.X - step, position.Y);
var mirrorOnRight = IsMirrorAt(position.X + step, position.Y);
reflectionOnX = mirrorOnLeft || mirrorOnRight;
reflectionOnY = false;
}
else if (IsMirrorAt(position.X, position.Y))
{
Log("ray is destroyed");
return false;
}
else
{
reflectionOnY = false;
reflectionOnX = false;
}
if (position.X <= 1 || position.X >= grid.GetLength(0) - 1) Debug.Assert(reflectionOnX);
if (position.Y <= 1 || position.Y >= grid.GetLength(1) - 1) Debug.Assert(reflectionOnY);
if (reflectionOnX) Log("reflection on Y");
if (reflectionOnY) Log("reflection on Y");
direction = new Direction(
direction.Dx * (reflectionOnX ? -1 : 1),
direction.Dy * (reflectionOnY ? -1 : 1));
}
}
