protected void BuildTriangleList()
{
if (_TriangleList != null)
return;
_TriangleList = new List<MappingGridTriangle>[this._mapPoints.Length];
for (int i = 0; i < _TriangleIndiciesCache.Length; i += 3)
{
int iOne = _TriangleIndiciesCache[i];
int iTwo = _TriangleIndiciesCache[i + 1];
int iThree = _TriangleIndiciesCache[i + 2];
//Safe to go straight into the cache since we looked at TriangleIndicies to initialize list
MappingGridTriangle newTri = new MappingGridTriangle(mapPoints,
_TriangleIndiciesCache[i],
_TriangleIndiciesCache[i + 1],
_TriangleIndiciesCache[i + 2]);
//Get the list for each point and add a reference to the triangle
if (_TriangleList[iOne] == null)
{
_TriangleList[iOne] = new List<MappingGridTriangle>(6);
}
_TriangleList[iOne].Add(newTri);
if (_TriangleList[iTwo] == null)
{
_TriangleList[iTwo] = new List<MappingGridTriangle>(6);
}
_TriangleList[iTwo].Add(newTri);
if (_TriangleList[iThree] == null)
{
_TriangleList[iThree] = new List<MappingGridTriangle>(6);
}
_TriangleList[iThree].Add(newTri);
}
}
public static MappingGridTriangle TriangleForPoint(int GridSizeX, int GridSizeY, GridRectangle Bounds, MappingGridVector2[] points, int[] TriIndicies, GridVector2 Point)
{
//Having a smaller epsilon caused false positives.
//We just want to know if we are close enough to check with the more time consuming math
double epsilon = 5;
if (Point.X < Bounds.Left - epsilon)
return null;
if (Point.X > Bounds.Right + epsilon)
return null;
if (Point.Y > Bounds.Top + epsilon)
return null;
if (Point.Y < Bounds.Bottom - epsilon)
return null;
double OffsetX = Point.X - Bounds.Left;
double OffsetY = Point.Y - Bounds.Bottom;
double X = (OffsetX / Bounds.Width) * (GridSizeX-1);
double Y = (OffsetY / Bounds.Height) * (GridSizeY-1);
int iX = (int)X;
int iY = (int)Y;
//This gives us the grid coordinates which contains two triangles, however there are two triangles. If the fractional parts add up to a number greater than one it is the upper triangle.
bool IsUpper = (X - iX) + (Y - iY) > 1;
//Check edge case where point is exactly on the right edge of the boundary
if (OffsetX + double.Epsilon >= Bounds.Width )
{
IsUpper = true;
iX--;
}
else if (OffsetY + double.Epsilon >= Bounds.Height)
{
IsUpper = true;
iY--;
}
else
{
IsUpper = (X - iX) + (Y - iY) > 1;
}
int iTri = (iY * 2) + ((GridSizeY-1) * 2 * iX);
//int iTri = (iX * 2) + ((GridSizeX-1) * 2 * iY);
iTri += IsUpper ? 1:0;
iTri *= 3;//Multiply by three to get the triangle offset
MappingGridTriangle mapTri = new MappingGridTriangle(points, TriIndicies[iTri], TriIndicies[iTri + 1], TriIndicies[iTri + 2]);
Debug.Assert(mapTri.IntersectsMapped(Point), "Calculated GridTransform does not intersect requested point");
return mapTri;
}
