A Free-Space Diffraction BSDF

Shlomi Steinberg
Arshiya Mollazainali
ACM Transactions on Graphics (Proceedings of SIGGRAPH 2024)

To Appear

Path tracing simulation of signal coverage. (a) We simulate the propagation of cellular radiation (λ = 10 cm) in an urban scene, consisting of various buildings. The light source is placed on top of the highlighted antenna. (b) Also shown is a top-down view upon the region shadowed by the large buildings. Visualized is the colour-coded irradiance impinging upon the visible surfaces. The scene consists of 181 000 triangles, and the meshes were not optimized for long-wavelength rendering: they admit many small details and wavelength-scale edges, making the computations of free-space diffractions expensive. For comparison, displayed are the ray optics-only renderings. Observe the difference (compared with ray optics) insets: the long-wavelength radiation diffracts around the building edge’s into the shadow regions, yielding a signal distribution that deviates sharply from the ray optics-only simulation. Also notice the multiple interactions (reflections and diffractions) of radiation with the scene—effects which are very difficult to simulate with existing methods.