/// <summary>
/// Calculate the closest distance to a track, as well as the 'longitude' along it.
/// </summary>
/// <param name="trackVectorSection">The vectorsection for which we want to know the distance</param>
/// <param name="trackSection">The corresponding tracksection</param>
/// <returns>Distance Squared to the track as well as length along track.</returns>
/// <remarks>Partly the same code as in Traveller.cs, but here no culling, and we just want the distance.
/// The math here is not perfect (it is quite difficult to calculate the distances to a curved line
/// for all possibilities) but good enough. The math was designed (in Traveller.cs) to work well for close distances.
/// Math is modified to prevent NaN and to combine straight and curved tracks.</remarks>
DistanceLon CalcRealDistanceSquared(TrVectorSection trackVectorSection, TrackSection trackSection)
{
//Calculate the vector from start of track to the mouse
Vector3 vectorToMouse = new Vector3
{
X = storedMouseLocation.Location.X - trackVectorSection.X,
Z = storedMouseLocation.Location.Z - trackVectorSection.Z
};
vectorToMouse.X += (storedMouseLocation.TileX - trackVectorSection.TileX) * 2048;
vectorToMouse.Z += (storedMouseLocation.TileZ - trackVectorSection.TileZ) * 2048;
//Now rotate the vector such that a direction along the track is in a direction (x=0, z=1)
vectorToMouse = Vector3.Transform(vectorToMouse, Matrix.CreateRotationY(-trackVectorSection.AY));
float lon, lat;
if (trackSection.SectionCurve == null)
{
//Track is straight. In this coordinate system, the distance along track (lon) and orthogonal to track (lat) are easy.
lon = vectorToMouse.Z;
lat = vectorToMouse.X;
}
else
{
// make sure the vector is as if the vector section turns to the left.
// The center of the curved track is now a (x=-radius, z=0), track starting at (0,0), pointing in positive Z
if (trackSection.SectionCurve.Angle > 0)
{
vectorToMouse.X *= -1;
}
//make vector relative to center of curve. Track now starts at (radius,0)
vectorToMouse.X += trackSection.SectionCurve.Radius;
float radiansAlongCurve = (float)Math.Atan2(vectorToMouse.Z, vectorToMouse.X);
//The following calculations make sense when close to the track. Otherwise they are not necessarily sensible, but at least well-defined.
// Distance from mouse to circle through track section.
lat = (float)Math.Sqrt(vectorToMouse.X * vectorToMouse.X + vectorToMouse.Z * vectorToMouse.Z) - trackSection.SectionCurve.Radius;
lon = radiansAlongCurve * trackSection.SectionCurve.Radius;
}
float trackSectionLength = DrawTrackDB.GetLength(trackSection);
if (lon < 0)
{ // distance from start of track
return(new DistanceLon(lat * lat + lon * lon, 0));
}
if (lon > trackSectionLength)
{ // distance from end of track
return(new DistanceLon(lat * lat + (lon - trackSectionLength) * (lon - trackSectionLength), trackSectionLength)); //idem
}
// somewhere along track. Distance is only in lateral direction
return(new DistanceLon(lat * lat, lon));
}
/// <summary>
/// Find the exact distance of the start of the current tracksection (from the beginning of the vector node)
/// </summary>
/// <returns></returns>
private float GetSectionStartDistance()
{
float distanceFromStart = 0;
TrackVectorNode tn = TrackDB.TrackNodes[TvnIndex] as TrackVectorNode;
for (int tvsi = 0; tvsi < TrackVectorSectionIndex; tvsi++)
{
TrackVectorSection tvs = tn.TrackVectorSections[tvsi];
TrackSection trackSection = TsectionDat.TrackSections.Get(tvs.SectionIndex);
if (trackSection != null) // if trackSection is missing somehow, well, do without.
{
distanceFromStart += DrawTrackDB.GetLength(trackSection);
}
}
return(distanceFromStart);
}