Schuwi ff69c1d2db Add OpenStreetMap base layer with Carto tile overlay ...

- Fetch Carto Voyager no-label base tiles and label-only tiles separately,
  cached under cache/osm_tiles/{z}/ and cache/osm_tiles/labels/{z}/
- Rasterize both into the orthographic projection via exact inverse projection
  (new unproject/pixel_to_geo methods on OrthoProjection)
- Render pipeline: basemap → cloud blend → label overlay (labels above clouds)
- Bilinear interpolation for base tiles; premultiplied-alpha bilinear for label
  tiles to prevent dark-fringe artifacts at text edges
- Dynamic zoom selection (floor-based) from actual geographic bounding box
- Fix horizontal squish: derive HALF_W_DEG from pixel aspect ratio so
  degrees-per-pixel is equal on both axes
- Add --no-basemap flag to skip tile fetching for offline/fast use
- Remove hardcoded city markers/labels when tile label overlay is present

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

2026-03-07 10:52:34 +01:00

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