public static float extrapolateLinear(float scale, float startValue, float endValue) {
//        if (scale <= 0f) {
//            return startValue;
//        }
        return ((1f - scale) * startValue) + (scale * endValue);
    }
Linear extrapolation from startValue to endValue by the given scale.
if scale is between 0 and 1 this method returns the same result as interpolateLinear
if the scale is over 1 the value is linearly extrapolated.
Note that the end value is the value for a scale of 1.

@param scale the scale for extrapolation
@param startValue the starting value (scale = 0)
@param endValue the end value (scale = 1)
@return an extrapolation for the given parameters
jme3-core/src/main/java/com/jme3/math/FastMath.java