public double this[double x, double y]
{
get
{
x *= _scaleFactor;
y *= _scaleFactor;
double value = 0;
double x0, x1, y0, y1;
/* We implement a high-pass filter by subtracting a blurred version of the noise from itself. */
x0 = Math.Ceiling(x - _blurFactor * CutOffDistance);
y0 = Math.Ceiling(y - _blurFactor * CutOffDistance);
x1 = Math.Floor(x + _blurFactor * CutOffDistance);
y1 = Math.Floor(y + _blurFactor * CutOffDistance);
for (var xi = x0; xi <= x1; ++xi)
{
var squaredDistanceX = ExtraMath.Square(x - xi);
for (var yi = y0; yi <= y1; ++yi)
{
var squaredDistance = ExtraMath.Square(y - yi) + squaredDistanceX;
value -= GetWeight(squaredDistance * _blurNormalizationFactor) * GetValue(_seedHash[xi][yi]);
}
}
value *= _blurNormalizationFactor;
/* We implement a low-pass filter by simply only sampling the noise function at certain intervals. */
x0 = Math.Ceiling(x - CutOffDistance);
y0 = Math.Ceiling(y - CutOffDistance);
x1 = Math.Floor(x + CutOffDistance);
y1 = Math.Floor(y + CutOffDistance);
for (var xi = x0; xi <= x1; ++xi)
{
var squaredDistanceX = ExtraMath.Square(x - xi);
for (var yi = y0; yi <= y1; ++yi)
{
var squaredDistance = ExtraMath.Square(y - yi) + squaredDistanceX;
value += GetWeight(squaredDistance) * GetValue(_seedHash[xi][yi]);
}
}
return(value);
}
}
private void SetUpScreen(RenderInfo renderInfo)
{
float diagonalFactor = (float)(_uiDiagonal / Math.Sqrt(ExtraMath.Square(renderInfo.Width) + ExtraMath.Square(renderInfo.Height)));
Width = renderInfo.Width * diagonalFactor;
Height = renderInfo.Height * diagonalFactor;
GL.MatrixMode(MatrixMode.Projection);
GL.LoadIdentity();
var modelViewMatrix = Matrix4.Zero;
modelViewMatrix.M11 = 2.0f / Width;
modelViewMatrix.M41 = -1.0f;
modelViewMatrix.M22 = -2.0f / Height;
modelViewMatrix.M42 = 1.0f;
modelViewMatrix.M33 = 1;
modelViewMatrix.M44 = 1;
GL.MatrixMode(MatrixMode.Modelview);
GL.LoadMatrix(ref modelViewMatrix);
}
