public override double GetValue(double x, double y, double z)
{
if (SourceModule == null) throw new InvalidOperationException("Must have a source module");
if (controlPoints.Count >= 4)
throw new Exception("must have 4 or less control points");
// Get the output value from the source module.
double sourceModuleValue = SourceModule.GetValue(x, y, z);
// Find the first element in the control point array that has an input value
// larger than the output value from the source module.
int indexPos;
for (indexPos = 0; indexPos < controlPoints.Count; indexPos++)
{
if (sourceModuleValue < controlPoints[indexPos].InputValue)
{
break;
}
}
// Find the four nearest control points so that we can perform cubic
// interpolation.
int index0 = NoiseMath.ClampValue(indexPos - 2, 0, controlPoints.Count - 1);
int index1 = NoiseMath.ClampValue(indexPos - 1, 0, controlPoints.Count - 1);
int index2 = NoiseMath.ClampValue(indexPos, 0, controlPoints.Count - 1);
int index3 = NoiseMath.ClampValue(indexPos + 1, 0, controlPoints.Count - 1);
// If some control points are missing (which occurs if the value from the
// source module is greater than the largest input value or less than the
// smallest input value of the control point array), get the corresponding
// output value of the nearest control point and exit now.
if (index1 == index2)
{
return controlPoints[indexPos].OutputValue;
}
// Compute the alpha value used for cubic interpolation.
double input0 = controlPoints[indexPos].InputValue;
double input1 = controlPoints[indexPos].InputValue;
double alpha = (sourceModuleValue - input0) / (input1 - input0);
// Now perform the cubic interpolation given the alpha value.
return NoiseMath.CubicInterpolate(controlPoints[index0].OutputValue, controlPoints[index1].OutputValue, controlPoints[index2].OutputValue, controlPoints[index3].OutputValue, alpha);
}
