Ray-based methods such as ray tracing and ray launching have been increasingly used in radio wave propagation modelling. Ray tracing is used for point-to-point multipath prediction (for few receivers) while ray launching, being more adaptable, is more suitable for multi-point prediction. However, ray launching suffers from angular dispersion which causes rays to miss pixels when the distance from the emitter increases. Several solutions such as beam tracing or ray splitting have been proposed to resolve this, but this paper presents a new approach, which is suitable for discrete ray launching, to avoid the problem. Results show that by this approach, discrete ray launching is suitable for radio wave propagation modelling. Significant speedups are observed compared to traditional ray-based models via parallelization techniques such as multi-threading and distributed computing. Complex channel characteristics due to multipaths in the urban environment can be obtained via this method.