public static float getMipFromRoughness(float roughness, int miptot) {
        return FastMath.sqrt(roughness) * (miptot - 1);
    }
Computes the texture coordinates and the face of the cube map from the
given vector

@param texelVect the vector to fetch texels from the cube map
@param fixSeamsMethod the method to fix the seams
@param mapSize the size of one face of the cube map
@param store a Vector2f where the texture coordinates will be stored
@return the face from which to fetch the texel
jme3-core/src/main/java/com/jme3/environment/util/EnvMapUtils.java