void setSmoothInterpolation(bool b);

Sets whether to use spline or bilinear/linear surface interpolation.

The data points for the contour layer are samples of the z values at certain gridded or scattered (x, y) points. However, to draw the contour and to color the layer, it is necessarily to know the z values at all pixels in the xy plane. ChartDirector uses surface interpolation to compute the z values at all pixels from the given data points.

In spline surface interpolation, ChartDirector will compute a smooth surface that passes through all data points. In bilinear/linear surface interpolation, ChartDirector will use the data points to partition the (x, y) plane into rectangular or triangular regions, and will fit bilinear or linear surfaces to the regions.

Spline surface interpolation generally produces smoother contours and is the default.

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