public static float invSqrt(float fValue) {
        return (float) (1.0f / Math.sqrt(fValue));
    }
Returns 1/sqrt(fValue)

@param fValue The value to process.
@return 1/sqrt(fValue)
@see java.lang.Math#sqrt(double)
jme3-core/src/main/java/com/jme3/math/FastMath.java