public float CalculateTerrainHeight(float feetNorth, float feetEast, uint lod)
{
int col;
int row;
var feetAcross = _distanceBetweenElevationPostsCalculator.GetNumFeetBetweenElevationPosts(lod);
//determine the column and row in the DTED matrix where the nearest elevation post can be found
_nearestElevationPostColumnAndRowCalculator.GetNearestElevationPostColumnAndRowForNorthEastCoordinates(feetNorth, feetEast, lod, out col, out row);
//retrieve the 4 elevation posts which form a box around our current position (origin point x=0,y=0 is in lower left)
var Q11 = _columnAndRowElevationPostRecordRetriever.GetElevationPostRecordByColumnAndRow(col, row, lod);
var Q21 = _columnAndRowElevationPostRecordRetriever.GetElevationPostRecordByColumnAndRow(col + 1, row, lod);
var Q22 = _columnAndRowElevationPostRecordRetriever.GetElevationPostRecordByColumnAndRow(col + 1, row + 1, lod);
var Q12 = _columnAndRowElevationPostRecordRetriever.GetElevationPostRecordByColumnAndRow(col, row + 1, lod);
if (Q11 == null || Q21 == null || Q22 == null || Q12 == null)
{
return(0);
}
//determine the North/East coordinates of these 4 posts, respectively
var Q11North = row * feetAcross;
var Q11East = col * feetAcross;
float FQ11 = Q11.Elevation;
var Q21East = (col + 1) * feetAcross;
float FQ21 = Q21.Elevation;
float FQ22 = Q22.Elevation;
var Q12North = (row + 1) * feetAcross;
float FQ12 = Q12.Elevation;
//perform bilinear interpolation on the 4 outer elevation posts relative to our actual center post
//see: http://en.wikipedia.org/wiki/Bilinear_interpolation
var x = feetEast;
var y = feetNorth;
var x1 = Q11East;
var x2 = Q21East;
var y1 = Q11North;
var y2 = Q12North;
var result =
(
((FQ11 / ((x2 - x1) * (y2 - y1))) * (x2 - x) * (y2 - y))
+
((FQ21 / ((x2 - x1) * (y2 - y1))) * (x - x1) * (y2 - y))
+
((FQ12 / ((x2 - x1) * (y2 - y1))) * (x2 - x) * (y - y1))
+
((FQ22 / ((x2 - x1) * (y2 - y1))) * (x - x1) * (y - y1))
);
return(result);
}
public Bitmap GetDetailTextureForElevationPost(int postCol, int postRow, uint lod)
{
var col = postCol;
var row = postRow;
_elevationPostCoordinateClamper.ClampElevationPostCoordinates(ref col, ref row, lod);
if (postCol != col || postRow != row)
{
col = 0;
row = 0;
}
var lRecord = _columnAndRowElevationPostRetriever.GetElevationPostRecordByColumnAndRow(col, row, lod);
if (lRecord == null)
{
return(null);
}
var textureId = lRecord.TextureId;
var bigTexture = _terrainTextureByTextureIdRetriever.GetTerrainTextureByTextureId(textureId, lod);
Bitmap toReturn;
if (lod <= _terrainDB.TheaterDotMap.LastNearTiledLOD)
{
var chunksWide = 4 >> (int)lod;
var thisChunkXIndex = (uint)(col % chunksWide);
var thisChunkYIndex = (uint)(row % chunksWide);
var leftX = (int)(thisChunkXIndex * (bigTexture.Width / chunksWide));
var rightX = (int)((thisChunkXIndex + 1) * (bigTexture.Width / chunksWide)) - 1;
var topY = (int)(bigTexture.Height - (thisChunkYIndex + 1) * (bigTexture.Height / chunksWide));
var bottomY = (int)(bigTexture.Height - thisChunkYIndex * (bigTexture.Height / chunksWide)) - 1;
var sourceRect = new Rectangle(leftX, topY, (rightX - leftX) + 1, (bottomY - topY) + 1);
toReturn = (Bitmap)Util.CropBitmap(bigTexture, sourceRect);
bigTexture.Dispose();
}
else
{
toReturn = bigTexture;
}
return(toReturn);
}
public TheaterDotLxFileRecord GetElevationPostRecordByColumnAndRow(int postColumn, int postRow, uint lod)
{
return(_columnAndRowElevationPostRecordRetriever.GetElevationPostRecordByColumnAndRow(postColumn, postRow, lod));
}