Added stars at L1

readme.md

@@ -121,7 +121,14 @@ comes from the LRO Camera's normalized-reflectance mosaic, which
 `scripts/fetch-moon.py` downloads (1.2 GB) and assembles (with numpy and Pillow)
 into `data/moon/wac-hapke-643.png`. The Moon is turned by the scene's epoch, or
 by `moon_attitude` in a scene without one (by default facing Earth, which can
-be off by up to about 10 degrees).
+be off by up to about 10 degrees). Also at lighting L1, and shown by camera C1,
+stars come from the Hipparcos, Tycho-2 and Gaia DR3 catalogs, which `scripts/fetch-stars.py` downloads (210 MB of
+files and 2.3 GB of Gaia queries, about an hour) and merges into
+`data/stars/stars.bin` (590 MB, 37 million stars to G 15); their proper motion
+is taken to the scene's epoch, or J2000 in a scene without one. The CLI loads
+only the stars bright enough to show at the camera's exposure.
+`stars-pleiades.toml` is a star field, and `geo-telescope-*.toml` a telescope
+on one geostationary satellite imaging another against the stars.
 
 ```sh
 cargo run --release -p resolved-cli -- render \
@@ -166,8 +173,8 @@ cargo run --release -p resolved-showcase -- --serve 0.0.0.0:8010
   L0 and C0). `--supersampling N` renders each pixel as N x N finer ones from C1
   (default 2). A tier the scene or the data cannot support stops with an error
   naming what is missing.
-- `--data DIR` says where the tiers' data is (`earth/bmng-2004-MM.jpg` and
-  `moon/wac-hapke-643.png`).
+- `--data DIR` says where the tiers' data is (`earth/bmng-2004-MM.jpg`,
+  `moon/wac-hapke-643.png` and `stars/stars.bin`).
   Without it the CLI tries `RESOLVED_DATA`, then `./data`, then the
   repository's `data/`.
 - `--adapter` takes `auto`, `gpu`, `cpu` or part of an adapter's name;
@@ -191,14 +198,14 @@ Lighting L0 and L1 and camera C0 are in: the library renders Earth, Moon, Sun
 and targets to DN through `Renderer`, and the CLI renders scene files. Lighting
 L1 draws Earth's surface from Blue Marble and the Moon's from the LRO Camera's
 map, shadows on the target, light from Earth and the Moon on it, eclipses on
-Earth and the Moon, and the Sun's limb darkening. Camera C1 is under way: so
-far, pixels that collect light over their area, lens distortion
-(Brown-Conrady), lens blur (a Gaussian PSF) applied to the scene rendered
-2 x 2 finer than the pixels, and the Sun, Moon and Earth at their apparent
-positions (light time and aberration). Planned, in order:
+Earth and the Moon, the Sun's limb darkening, and stars from Hipparcos,
+Tycho-2 and Gaia, which camera C1 shows. Camera C1 is under way: so far,
+pixels that collect light over their area, lens distortion (Brown-Conrady),
+lens blur (a Gaussian PSF) applied to the scene rendered 2 x 2 finer than the
+pixels, and the Sun, Moon and Earth at their apparent positions (light time
+and aberration). Planned, in order:
 
-- Camera: stars,
-  detector noise, pixel-to-pixel variation, saturation and blooming.
+- Camera: detector noise, pixel-to-pixel variation, saturation and blooming.
 - Lighting: BRDF and spectral materials, atmospheric scattering, clouds, lunar
   terrain.
 - Portable ray tracing, path tracing, and label outputs for ML.