/// <summary>
/// Get the cell slope in radians based on its circular neighborhood. The results is the angle between vertical axis and normal of the cell.
/// E.g. 0 = cell is completely flat, pi/2 = the cell is a vertical wall.
/// </summary>
/// <param name="cellY">Y coordinate of the cell</param>
/// <param name="cellX">X coordinate of the cell</param>
/// <returns>Cell slope in radians</returns>
private double GetCellSlope(int cellY, int cellX)
{
double cn = Math.Sqrt(2);
double northsouth;
double eastwest;
if (cellX <= 0 || cellY <= 0 || cellX >= ElevationMap.GetLength(1) - 1 || cellY >= ElevationMap.GetLength(0) - 1)
{
return(0);
}
try {
northsouth = (cn * ElevationMap[cellY - 1, cellX - 1] + ElevationMap[cellY - 1, cellX] + cn * ElevationMap[cellY - 1, cellX + 1]) / 4
- (cn * ElevationMap[cellY + 1, cellX - 1] + ElevationMap[cellY + 1, cellX] + cn * ElevationMap[cellY + 1, cellX + 1]) / 4;
eastwest = (cn * ElevationMap[cellY - 1, cellX - 1] + ElevationMap[cellY, cellX - 1] + cn * ElevationMap[cellY + 1, cellX - 1]) / 4
- (cn * ElevationMap[cellY - 1, cellX + 1] + ElevationMap[cellY, cellX + 1] + cn * ElevationMap[cellY + 1, cellX + 1]) / 4;
} catch (IndexOutOfRangeException) {
System.Diagnostics.Debug.WriteLine("{0}, {1}", cellX, cellY);
return(0);
}
Vector3 northVector = Vector3.Normalize(new Vector3(0, 2 * (float)cellResolution, (float)northsouth));
Vector3 eastVector = Vector3.Normalize(new Vector3(2 * (float)cellResolution, 0, (float)eastwest));
Vector3 slopeVector = Vector3.Cross(eastVector, northVector);
return(GetVectorAngle(slopeVector, verticalVector));
}
/// <summary>
/// Calculate West-East and North-South components of the cell slope.
/// </summary>
/// <param name="cellY">Y coordinate of the cell</param>
/// <param name="cellX">X coordinate of the cell</param>
/// <param name="westeast">output West-East component</param>
/// <param name="southnorth">output North-South component</param>
private void GetCellSlopeComponents(int cellY, int cellX, out double eastwest, out double northsouth)
{
double cn = Math.Sqrt(2);
if (cellX <= 0 || cellY <= 0 || cellX >= ElevationMap.GetLength(1) - 1 || cellY >= ElevationMap.GetLength(0) - 1)
{
northsouth = eastwest = 0;
return;
}
try {
northsouth = (cn * ElevationMap[cellY - 1, cellX - 1] + ElevationMap[cellY - 1, cellX] + cn * ElevationMap[cellY - 1, cellX + 1]) / 4
- (cn * ElevationMap[cellY + 1, cellX - 1] + ElevationMap[cellY + 1, cellX] + cn * ElevationMap[cellY + 1, cellX + 1]) / 4;
eastwest = (cn * ElevationMap[cellY - 1, cellX - 1] + ElevationMap[cellY, cellX - 1] + cn * ElevationMap[cellY + 1, cellX - 1]) / 4
- (cn * ElevationMap[cellY - 1, cellX + 1] + ElevationMap[cellY, cellX + 1] + cn * ElevationMap[cellY + 1, cellX + 1]) / 4;
} catch (IndexOutOfRangeException) {
System.Diagnostics.Debug.WriteLine("{0}, {1}", cellX, cellY);
northsouth = eastwest = 0;
}
}