In room acoustic modeling, feedback delay networks (FDN) are known to efficiently model late reverberation due to their capacity to generate exponentially decaying dense impulses. However, this method relies on a careful tuning of the different synthesis parameters, either estimated from a pre-recorded impulse response from the real acoustic scene, or set manually from experience. In this paper, we present a new method, which still inherits the efficiency of the FDN structure, but aims at linking the parameters of the FDN directly to the geometry setting. This relation is achieved by studying the sound energy exchange between each delay line using the acoustic radiance transfer method (RTM). Experimental results show that the late reverberation modeled by this method is in good agreement with the virtual geometry setting.