public float multProj(Vector3f vec, Vector3f store) {
        float vx = vec.x, vy = vec.y, vz = vec.z;
        store.x = m00 * vx + m01 * vy + m02 * vz + m03;
        store.y = m10 * vx + m11 * vy + m12 * vz + m13;
        store.z = m20 * vx + m21 * vy + m22 * vz + m23;
        return m30 * vx + m31 * vy + m32 * vz + m33;
    }
Apply this perspective transform to the specified Vector3f. Return the W
value, calculated by dotting the vector with the last row.

@param vec the vector to transform (not null, unaffected)
@param store storage for the result (not null, modified)
@return the W value
jme3-core/src/main/java/com/jme3/math/Matrix4f.java