Cosine interpolation is a simple method for approximating curvature while interpolating between two points. Similar to linear interpolation, this method is useful for when a straight-line interpolation is not adequate, yet a full cubic interpolation method might be inappropriate.
## Related Topics

LinearInterpolation
CubicInterpolation

Like linear interpolation, cubic interpolation takes a parameter **t**, and evaluates that parameter to an intermediate location between two points, **p0** and **p1**. Unlike linear interpolation, a little bit of math is tossed in to give the function a little but of curvature. It is not realistic curvature; the function, evaluated over a continuous set of control points, will exhibit peaks and discontinuities. But those discontinuities are typically small, and may not be noticable.

The method for cosine interpolation is:

pi=3.1415927 f = t * pi g = (1 - cos(f)) * 0.5 P(t)=p0+g*(p1-p0)

As you can see, **g** is calculated as a fudge-factor based on **t**, then is plugged straight in as a linear interpolant between **p0** and **p1**. The cos() operation imparts it a bit of a curve.

For a graph showing the differences between these 3 types of interpolation, see InterpolationComparison.