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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>
…s the render horizonator_project() (used by annotator.c to predict where a named POI should land on screen) computed the apparent elevation from a raw lat/lon/ele difference, with no Earth-curvature/refraction correction. When a render was made with horizonator_set_curvature() enabled, the actual terrain in that render sits lower than this flat-plane projection predicts -- by over a kilometer of apparent height at 100+km. annotator.c's occlusion/matching search (a small pixel-radius, range-difference fuzz match) can't bridge that gap, so with --curvature, no POIs were ever found: every one looked occluded. horizonator_project() now takes curvature_enabled/refraction_k and applies the same drop = (1-k)*d^2/(2*Rearth) subtracted from the apparent height, matching vertex.glsl. annotate() takes and forwards the same two values, which must match whatever was passed to horizonator_set_curvature() for the render being annotated. horizonator_unproject() needs no equivalent change: it derives lat/lon from the already-rendered (already curvature-corrected, if enabled) range image, not from an independently-computed real-world height. Also fixes query-peaks-from-osm.py, which the Overpass API was rejecting (HTTP 406) or timing out on: switch to https, add an identifying User-Agent and an explicit query timeout. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
…100km MAX_MARKER_DIST was a #define fixed at 100000.0, independent of the render's own --zfar. Any POI farther than 100km was silently never labelled, even if it was actually rendered and clearly visible (e.g. Mont Blanc, 158km from Lyon, with a --zfar of 150km+). annotate() now takes max_marker_dist_m explicitly; standalone passes zfar, since there's no point labelling something farther than what was actually rendered. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Switches the default look from the original blue-background/red-distance color-coding to a udeuschle.de-style drawn panorama: a white background, near terrain in dark gray fading to light gray/white far away, and the crest of each visible ridge/mountain-range layer outlined in a dark gray line. - horizonator-lib.c: glClearColor() to white instead of blue - vertex.glsl: rgb is now a grayscale value (GRAY_NEAR..GRAY_FAR by distance) on all 3 channels, instead of red-only - standalone.c: new draw_ridge_outlines(), a CPU-side post-process on the already-available range image. Darkens a pixel to --ridge-line-gray wherever it sits at a depth discontinuity of more than --ridge-line-threshold meters from the pixel above it (terrain against the sky, or one surface abruptly replaced by a much nearer/farther one behind a gap). Deliberately uses an absolute meters threshold, not a fraction of distance: at the bottom of the frame (grazing, near-horizontal sightlines) a fixed threshold naturally produces more, finer ridgelets than near the horizon, matching what a real drawn panorama looks like up close. --no-ridge-lines disables this. Also rewrites standalone --help and the corresponding README section into a single, organized reference for every rendering option and how it affects the output (field of view, curvature/refraction, color/ridge lines, peak labels, viewer position, performance, data sources). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
The peak-visibility-matching logic (project each POI, then scan the
rendered range image to confirm it isn't occluded) was inlined in
annotate(), entangled with the PDF/SVG drawing code -- there was no way
to get just the list of visible peaks without generating a full
annotated render.
Extracts that logic into find_visible_pois(), a new function in
annotator.c/.h that annotate() now calls internally (no behavior
change, no more duplicated code). standalone gets a new
--list-visible-peaks OUT.txt option, independent of --image, that
writes the visible peaks (name, lat, lon, ele_m, range_m) as a plain
tab-separated file.
Also fixes a latent NULL-dereference: strlen(filename_image) was called
unconditionally, before checking filename_image for NULL. This was
never reached with a NULL filename_image before (every prior path
through this code already required --image), but --list-visible-peaks
without --image hits it directly.
cluster-visible-peaks.py is a companion script: reads that output,
drops peaks with no letters in their name (OSM-nameless fallback
entries, e.g. "1583.0"), and groups the rest into geographic clusters
("massifs" -- OSM doesn't reliably tag this for this area, so these are
unnamed, distance-ordered groups, not real massif names).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Adds directional slope shading: terrain is darkened/lightened based on how its surface faces relative to a light direction, giving the relief a 3D appearance beyond the existing pure distance-based grayscale. Normals are estimated per-vertex, on the CPU, by finite differences over the 4 DEM neighbors of each grid point (horizonator-lib.c, in the existing vertex-buffer-filling loop -- no extra DEM reads, the samples are already being fetched there). They're uploaded as a second vertex attribute (a new float VBO; the existing position VBO stays untouched, compact GLshorts) and interpolated by the rasterizer across each triangle. This means shading is continuous across the edge between two triangles sharing a vertex, unlike a flat per-triangle normal, which would show a visible facet at every triangle boundary. Lighting itself (dot(normal,sun_dir), with a 0.5 ambient floor so a slope facing away from the sun dims rather than goes black) happens in fragment.glsl, using the interpolated per-fragment normal; geometry.glsl just passes normals through unchanged, one per vertex, alongside the existing rgb/tex passthrough. horizonator_set_sun(ctx, shading_enabled, sun_az_deg, sun_el_deg) is a new public function, following the same on/off + uniforms pattern as horizonator_set_curvature(): shading is off by default (unchanged legacy rendering) via a shading_scale uniform (0.0/1.0), same trick as curvature_scale. standalone gets matching --shading/--sun-azimuth/ --sun-elevation flags. Memory cost: +12 bytes/vertex (a float3 normal) for the *entire* loaded grid (Nvertices = (2*radius_cells)^2, independent of the azimuth-wedge mesh restriction, which only shrinks the triangle/index buffer, not the vertex buffer) -- e.g. +~250MB at a 150km zfar. This is a one-time allocation per render (standalone is single-shot: one init, one render, exit), not a repeated one, so it doesn't compound the way the known horizonator_deinit() leak does across repeated init/deinit cycles in one process. Tested at the 150km/4000x550 reference crop with no crash and stable memory. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
The distance-based color gradient (vertex.glsl) went from a dark gray near the viewer to a light gray far away, converging on the white background. Replaces GRAY_NEAR/GRAY_FAR with COLOR_NEAR/COLOR_FAR: near terrain stays the same dark neutral gray, but far terrain now fades towards a pale blue-gray instead of a neutral light gray, the way haze and atmospheric scattering tint distant relief blue in a real photo. Combines naturally with the slope-shading multiply in fragment.glsl (unchanged there). Updates the standalone --help COLOR section and the README to describe the new blue-tinted far color instead of the old "light gray". Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Replaces the neutral GRAY_NEAR/GRAY_FAR distance gradient with COLOR_NEAR/COLOR_FAR: far terrain now fades towards a pale blue-gray instead of a neutral light gray, mimicking how haze/atmospheric scattering tints distant relief blue in a real photo. Combines naturally with the slope-shading multiply from #11. Builds on #4-#11.