Various ray-tracing methods have been developed for wireless propagation predication. Most of them are hybrid 2D and 3D models (see Athanasiadou, G.E. and Nix, A.R., IEEE Trans. Veh. Technol., vol.49, no.4, p.1152-68, 2000; Liang, G. and Bertoni, H.L., IEEE Trans. Antennas Propagat., vol.46, no.6, p.853-63, 1998). They assume the walls are vertical, roofs and ceilings are horizontal and the ground is flat. These assumptions are not always true. This paper presents a new 3D ray-tracing method based on 3D geometry and vector calculations. Propagation path concepts of triangular reflection pyramid ray-tubes and diffraction hollow cones have been developed. This method applies to different terrains and both indoor and outdoor environments. Virtual reality (VR) is used to visualise the environments and line-of-sight (LOS) and non-LOS signal paths and allows us to verify the methods we used.