["Transactions in GIS, Volume 30, Issue 2, April 2026. ", "\nABSTRACT\nWireless network planning and optimization involves radio propagation modeling, which requires detailed terrain and building height data. In the past, raster‐based building rooftop height data extracted from building footprints has been used down to 1 m resolution. For numerical evaluation of diffraction loss in case of raster‐based input data, fast approximate algorithms are used, such as R2, XDraw, and their various implementations. Vector‐based 3D city models with a high level of detail have recently gained significant interest. However, existing vector‐data analysis algorithms are slow, and efficient numerical methods remain scarce. This work aims to develop a fast diffraction algorithm tailored to high‐accuracy 3D vector building data. In the proposed model, diffraction loss is computed in accordance with the ITU‐R P.526 recommendation, using the XDraw approximation to enable fast numerical processing. The algorithm runs in ON2$$ \\mathcal{O}\\left({N}^2\\right) $$ time by analyzing propagation in rings starting at the antenna location and progressing toward the edges of the analysis area. The performance and accuracy of the diffraction prediction model are benchmarked against the traditional raster‐based XDraw algorithm, with results calculated using the 3D BAG open dataset for the city of Amsterdam.\n"]