Fritsch, JonathanSchneegans, SimonFriederichs, FabianFlatken, MarkusEisemann, MartinGerndt, AndreasKnoll, AaronPeters, Christoph2025-06-202025-06-202025978-3-03868-291-22079-8687https://doi.org/10.2312/hpg.20251171https://diglib.eg.org/handle/10.2312/hpg20251171Shadows on large-scale terrains are important for many applications, including video games and scientific visualization. Yet real-time rendering of realistic soft shadows at planetary scale is a challenging task. Notably, many shadowing algorithms require keeping significant amounts of extra terrain geometry in memory to account for out-of-frustum occluders. We present Fourier-Compressed Horizon Mapping, an enhancement of the horizon mapping algorithm which is able to circumvent this requirement and render shadows in a single render pass. For a given digital elevation model, we create a compact representation of each pixel's horizon profile and use it to render soft shadows at runtime. This representation is based on a truncated Fourier series stored in a multi-resolution texture pyramid and can be encoded in a single four-channel 32 bit floating point texture. This makes this approach especially suitable for applications using a level-of-detail system for terrain rendering. By using a compact representation in frequency space, compressed horizon mapping consistently creates more accurate shadows compared to traditional horizon maps of the same memory footprint, while still running well at real-time frame rates.Attribution 4.0 International LicenseCCS Concepts: Computing methodologies → RenderingComputing methodologies → Rendering10.2312/hpg.2025117110 pages