Studies from public and environmental health show strong indication of the importance of visible urban green space. However, current approaches for modelling viewshed based greenness visibility still have high computation costs. Therefore, we propose an algorithm for point-based viewshed computation using a novel prototyping approach. Our evaluation shows an average improvement of 34%. We anticipate that these findings lay the groundwork for further optimisation of point-based viewshed computation, improving the feasibility of subsequent comparative studies in the field of public and environmental health.