private float HighPrecisionTerrainHeight(float meterx, float meterz, bool isLatlon)
{
double finalvalue = 0.0;
Vector2 c;
if (!isLatlon)
{
Geography proj = new Geography();
c = proj.meterstoLatLonDouble(meterx, meterz);
}
else
{
c = new Vector2(meterx, meterz);
}
double ratioX = Math.Ceiling(scenebbox.top) - c.x;
double ratioZ = c.y - Math.Floor(scenebbox.left);
double Xindex = (1200.0 * ratioX);
double Zindex = (1200.0 * ratioZ);
//Upper Triangle
if ((Xindex - Math.Floor(Xindex)) + (Zindex - Math.Floor(Zindex)) < 1.0f)
{
int n = heightmap.heightmap[(int)Math.Floor(Xindex), (int)Math.Ceiling(Zindex)];
int m = heightmap.heightmap[(int)Math.Floor(Xindex), (int)Math.Floor(Zindex)];
int k = heightmap.heightmap[(int)Math.Ceiling(Xindex), (int)Math.Floor(Zindex)];
double interpolationUp = m + (n - m) * (Zindex - Math.Floor(Zindex));
double interpolationHypothenus = k + (n - k) * (Zindex - Math.Floor(Zindex));
double a = Xindex - Math.Floor(Xindex);
double aplusb = Math.Ceiling(Zindex) - Zindex;
finalvalue = interpolationUp + (interpolationHypothenus - interpolationUp) * (a / aplusb);
}
//Lower Triangle
else if ((Xindex - Math.Floor(Xindex)) + (Zindex - Math.Floor(Zindex)) >= 1.0f)
{
int n = heightmap.heightmap[(int)Math.Ceiling(Xindex), (int)Math.Ceiling(Zindex)];
int m = heightmap.heightmap[(int)Math.Ceiling(Xindex), (int)Math.Floor(Zindex)];
int k = heightmap.heightmap[(int)Math.Floor(Xindex), (int)Math.Ceiling(Zindex)];
double interpolationDown = m + (n - m) * (Zindex - Math.Floor(Zindex));
double interpolationHypothenus = m + (k - m) * (Zindex - Math.Floor(Zindex));
double a = Math.Ceiling(Xindex) - Xindex;
double aplusb = Zindex - Math.Floor(Zindex);
finalvalue = interpolationDown + (interpolationHypothenus - interpolationDown) * (a / aplusb);
if ((Xindex - Math.Floor(Xindex)) + (Zindex - Math.Floor(Zindex)) > 0.99 && (Xindex - Math.Floor(Xindex)) + (Zindex - Math.Floor(Zindex)) < 1.01)
{
return((float)interpolationHypothenus);
}
}
return((float)finalvalue);
}