This paper presents a novel routing method called ray tracing. The method targets wireless nanonetworks, which are networks of nanometer-sized nodes with applications in various domains such as future medicine and metamaterial. Due to their tiny size, nanonodes have quite limited resources, in particular energy, and it is crucial to use as few resources as possible. In multi-hop nanonetworks, resource consumption for routing depends on several factors, such as the number of nodes that forward packets, and the number of packets sent and received. To reduce the energy used, in the proposed ray tracing routing, only the nodes that receive duplicate packets at the same time forward them. This leads to the selection of the forwarding nodes over a quasistraight line between the source and the destination, which can bend at the edges of the network. The proposed method is a major improvement over its previous version, aiming to fix several crucial issues such as double propagation, large forwarding angle, and die-out. Moreover, the applicability of ray tracing in heterogeneous and 3D nanonetworks is also analyzed and a practical application for the protocol is proposed. Extensive simulation results demonstrate the fixing of these issues, and the superiority of the proposed improved ray tracing algorithm over other routing methods in the long and narrow nanonetworks, such as blood vessels and branches.