public static float fastInvSqrt(float x) {
        float halfX = 0.5f * x;
        int i = Float.floatToIntBits(x); // get bits for floating value
        i = 0x5f375a86 - (i >> 1); // gives initial guess y0
        x = Float.intBitsToFloat(i); // convert bits back to float
        x = x * (1.5f - halfX * x * x); // Newton step, repeating increases accuracy
        return x;
    }
Quickly estimate 1/sqrt(fValue).

@param x the input value (&ge;0)
@return an approximate value for 1/sqrt(x)
jme3-core/src/main/java/com/jme3/math/FastMath.java