This work presents a new radio paths computation frame-work especially designed for complex indoor RF field prediction. We propose a new algorithm utilizing a geometric visibility graph of a building to traverse all possible bounded radio paths. These paths are needed to compute the signal strength as received at given receiver location. We have implemented the suggested algorithm and performed a set of experiments testing the radio paths over complex buildings. The main conclusion is that the new algorithm is both (i) Accurate: predicts the signal strength within complex buildings, (ii) Runtime efficient: can compute all relevant radio paths even on relatively complex structures comprised of thousands of walls in a matter of seconds.