/// <summary>
/// Check if and handle the starting line intersections
/// </summary>
/// <returns>true: starting line has been crossed for the second time -> curve is finished, false: otherweise</returns>
private bool handlePointerMoved_StartingLineX(Point currentPoint)
{
bool startingLineIntersected = VectorMath.CheckIf2LinesIntersect(mStartingLineCandidateLeftPoint, mStartingLineCandidateRightPoint, mPreviousPoint.Value, currentPoint);
if (startingLineIntersected)
{
// check if we have the right angle, i.e. y coordinates must always get less
if ((currentPoint.Y - mPreviousPoint.Value.Y) < 0)
{
// right direction
mNrStartingLineIntersected++;
if (mNrStartingLineIntersected == 2)
{
// we are done the starting line has been intersected in the right direction for the second time
CurvePaintingFinished();
return(true);
}
}
else
{
// wrong direction -> user needs to start drawing from scratch
SetInstructionText(true, ERROR_STARTING_LINE_X_WRONG_DIRECTION);
mTrackCreationState = trackCreationState.Error;
}
}
return(false);
}
/// <summary>
/// check if the starting line is crossed and return the direction
/// </summary>
private bool CheckIfStartingLineIsCrossed(IList <Point> routeGridPoints, Point gridPointClicked, out bool rightDirection)
{
if (routeGridPoints.Count < 2)
{
rightDirection = false;
// too few
return(false);
}
// determine if we are going in the right direction for the starting line
// right direction is from down to up, i.e. from a higher Y-coordinate to a lower
rightDirection = routeGridPoints.Last().Y > gridPointClicked.Y;
// does the clicked grid point actually lie on the starting line
if (IsGridPointOnStartingLine(gridPointClicked))
{
// yes it does, return true, no need to check for an intersection
return(true);
}
// for the intersection check we need to extend the starting line beyond the grid points
// as the starting line also includes the part which is left of the left grid point
// and which is right of the right grid point.
Point extendedLeft = new Point(startingLineGridPointLeft.X, startingLineGridPointLeft.Y);
if (extendedLeft.X > 0)
{
extendedLeft.X -= 1;
}
;
Point extendedRight = new Point(startingLineGridPointRight.X + 1, startingLineGridPointRight.Y);
// now check if the car has crossed has the finish line
return(VectorMath.CheckIf2LinesIntersect(extendedLeft, extendedRight, routeGridPoints.Last(), gridPointClicked));
}
/// <summary>
/// ray casting algorithm
/// https://en.wikipedia.org/wiki/Point_in_polygon#Ray_casting_algorithm
/// </summary>
private static bool Contains(Polygon polygon, Point location)
{
// nr of intersections
uint nrIntersects = 0;
Point horizontalLineLeft = new Point(0, location.Y);
Point horizontalLineRight = new Point(location.X, location.Y);
Point?oldPoint = null;
for (int index = 0; index < polygon.Points.Count; index++)
{
if (oldPoint.HasValue)
{
// construct Line and do intersection check
if (VectorMath.CheckIf2LinesIntersect(horizontalLineLeft, horizontalLineRight, oldPoint.Value, polygon.Points[index]))
{
nrIntersects++;
}
}
// save for next line
oldPoint = polygon.Points[index];
}
// first check if the first point of the polygon lies on the starting line
// which is the case for random generated polygon tracks
// we must not count this point twice...
if (polygon.Points[0].Y != location.Y)
{
// now check the last closing polygon line
if (VectorMath.CheckIf2LinesIntersect(horizontalLineLeft, horizontalLineRight, oldPoint.Value, polygon.Points[0]))
{
nrIntersects++;
}
}
// odd number means inside
return(nrIntersects % 2 == 1);
}
/// <summary>
/// check if 'oneLine' intersects with any line in 'lineColl'
/// </summary>
/// <param name="oneLine">the line to check for intersections with lineColl</param>
/// <param name="lineColl"></param>
/// <param name="position">if there is an intersection, this is the index (zero-based) of the first line that intersects</param>
/// <returns>true: an intersection was found, false: otherwise</returns>
internal static bool CheckIfLineIntersectsWithLineCollection(Line oneLine, IList <Line> lineColl, out int position)
{
bool intersectionFound = false;
position = -1;
Point oneLine01 = new Point(oneLine.X1, oneLine.Y1);
Point oneLine02 = new Point(oneLine.X2, oneLine.Y2);
for (int index = 0; (index < lineColl.Count) && (intersectionFound == false); index++)
{
Line lineInColl = lineColl[index];
Point lineColl01 = new Point(lineInColl.X1, lineInColl.Y1);
Point lineColl02 = new Point(lineInColl.X2, lineInColl.Y2);
if (VectorMath.CheckIf2LinesIntersect(oneLine01, oneLine02, lineColl01, lineColl02))
{
intersectionFound = true;
position = index;
}
}
return(intersectionFound);
}