As a method for simulating the behavior of light and sound, ray tracing now underpins many of the tools architects use to conceptualize, visualize, and evaluate building performance. Ray tracing can simulate highly realistic lighting, facilitating daylight calculations and producing photorealistic visuals for communicating with clients and stakeholders. Using ray-based models of sound, designers can now understand acoustic performance as something that can be visualized, measured, and predicted, providing insights into complex acoustic interactions. This chapter explores ray tracing and its impact on architectural design. By tracing its origins, computational foundations, and disciplinary applications, it highlights how the development of ray tracing has not only influenced tools and workflows but also the conceptual frameworks by which architects understand space, performance, and representation.