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Lets you account for the fact that the viewer isn't standing at ground level (e.g. an apartment floor), by reusing horizonator_move() to reposition the camera at ground_elevation + viewer_height after the usual auto-selected ground elevation is computed. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
…correction The renderer worked entirely in the tangent plane at the viewer, ignoring Earth's curvature. This is a good approximation at short range, but at the 100-150km distances relevant for viewing the Alps from Lyon, a distant peak's apparent elevation angle can be off by more than a kilometer of apparent height. Add the standard geodetic "curvature and refraction" correction: drop = (1-k) * distance^2 / (2*Rearth) subtracted from each vertex's apparent height, where k is the atmospheric refraction coefficient (k=0.13, the Gaussian refraction coefficient used by udeuschle.de, is the default). New horizonator_set_curvature() API, and --curvature / --refraction-k flags on standalone. Off by default, so existing behavior is unchanged unless --curvature is explicitly requested; this lets the flat-plane and curved renders be compared directly. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
…n use The renderer always built a mesh covering the full 360-degree circle of loaded DEM data, even for a render that only ever looks at a narrow azimuth wedge (e.g. a fixed 110-degree panorama). Most of that geometry was never visible and cost triangle-generation/vertex-shader time every frame for nothing. horizonator_init() takes 3 new parameters: restrict_mesh_azimuth, mesh_az_deg0, mesh_az_deg1. When set, only cells within that azimuth range (plus a 5-degree margin, plus a small radius always meshed near the viewer where per-cell azimuth changes too fast to test reliably) are triangulated; the rest of the loaded square is skipped in the index buffer. Vertex generation, DEM sampling and the shaders are untouched. standalone (a single fixed-wedge render per invocation) enables this by default, since the meshed wedge always matches the rendered wedge exactly -- verified pixel-identical output on 3 different az/height combinations, 36-44% faster wall-clock render time. Pass --no-restrict-mesh-azimuth to fall back to the old full-circle mesh. The interactive horizonator tool and the Python bindings pass restrict_mesh_azimuth=false, since they let the viewer pan around after the data is loaded, potentially outside whatever wedge was meshed at init time. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This was referenced Sep 4, 2026
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Only mesh the azimuth wedge actually rendered (plus a small margin), instead of the full 360-degree circle of loaded DEM data. Enabled by default in standalone (verified pixel-identical output, 36-44% faster). Interactive tool and Python bindings keep the old full-circle behavior since they allow panning after load. Builds on #4 and #5.