Channel simulators capitalizing on the ray-tracing (RT) principle are widely used in wireless communications for generating realistic channel data. By combining the RT algorithm for the signal propagation trajectories with electromagnetic (EM) equations, generalized channel impulse responses (CIRs) are obtained. This paper presents a novel three-dimensional (3D) RT simulator for emerging smart wireless environments, termed as WiThRay, which can be deployed for the performance assessment of various wireless communication techniques, such as channel estimation/tracking, beamforming, and localization, under realistic EM wave propagation conditions. Firstly, a comprehensive comparison of existing RT-based channel simulators is provided, highlighting their wearknesses and limitations for utilization with the latest technologies for the sixth-generation (6G) of wireless systems. The proposed WiThRay simulator modifies the RT algorithm to follow the Fermat's principle, thus, reducing computational complexity, and implements scattering ray calibration providing a precise solution for the analysis of EM propagation. In addition, differently from most of the available RT-based simulators, WiThRay incorporates reconfigurable intelligent surfaces (RISs), which are lately considered as the key technology for RIS-enabled smart wireless communications. We thoroughly show that channel data obtained from WiThRay match sufficiently well with the fundamental EM propagation theory of wireless channels. Furthermore, the proposed simulator was deployed to study the performance of uplink channel estimation in orthogonal frequency-division multiplexing systems, downlink multi-user beamforming, and RIS-enabled coverage extension. The WiThRay versatile simulator is available in open-source mode, facilitating its easy deployment from the wireless research community for developing and testing communications and signal processing techniques in 6G smart wireless environments.
