evolution of the first moment and uses a closure relation valid in the diffusion limit, which is an isotropic radiative pressure tensor. The equation is modified with an ad-hoc function (the flux limiter) in order to ensure that the radiative flux is valid in the free-streaming limit. This method is very useful in diffusive regions and have been used to study accretion discs [@ohsuga05] and star formation [@krumholz06]. Another method of closing the system is the variable Eddington tensor formalism. It gives better results than the flux-limited diffusion but are much more complex and costly because it requires the local resolution of the transfer equation at each timestep. The methods which employ the optically thin variable Eddington tensor approximation [@ga01] have been used to study cosmic reionization [@ga01; @ricotti02; @petkova09]. A locally evaluated Eddington tensor, called the M$_1$ model, has also been used to close the system [@heracles] and has applied to study cosmic reionization [@aubert08]. The accuracy of the moments methods is problem-dependent and is hard to judge in general situation. @petkova11 have developed a method that employs a direct discretisation of the RT equation in Boltzmann form with finite angular resolution on moving meshes. This method is advantageous 