Added stars at L1
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@@ -1,8 +1,10 @@
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#!/usr/bin/env python3
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"""Writes examples/scenes/<model>.toml for the NASA models fetch-models.sh downloads,
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and two scenes with Earth, the Moon and a spacecraft together (below):
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two scenes with Earth, the Moon and a spacecraft together (below):
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examples/scenes/earthrise.toml from lunar orbit and examples/scenes/moonrise.toml
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from geostationary height.
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from geostationary height, and scenes for the stars of camera tier C1: a star field,
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examples/scenes/stars-pleiades.toml, and a telescope on one geostationary satellite
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imaging another along the arc, examples/scenes/geo-telescope-*.toml.
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Every scene has the same composition: the spacecraft in an isometric view (the
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camera looks along its body (+1, +1, +1) diagonal, body +Z toward image up) with
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@@ -447,6 +449,135 @@ attitude = {fmt(quaternion(attitude), 9)}
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"""
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# Earth's orbital speed, m/s, and the geostationary orbital speed.
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EARTH_SPEED = 29.78e3
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GEO_SPEED = 3074.7
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# The telescope's longitude on the geostationary arc, degrees: looking along the arc
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# from here points at right ascension 103 degrees, where the Milky Way crosses the
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# equator in Monoceros, the densest stretch of the equator (190 stars per square degree
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# to V 12, against 50 where it crosses in Aquila, behind the dust of the Aquila Rift).
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GEO_LONGITUDE = 13.0
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# The ecliptic's north pole in the inertial (equatorial J2000) frame.
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ECLIPTIC_POLE = [0.0, -math.sin(math.radians(23.4393)), math.cos(math.radians(23.4393))]
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def earth_velocity(sun):
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"""Earth's velocity around the Sun when the Sun is in direction `sun`: along the
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ecliptic, a quarter turn ahead of the Sun's direction from Earth."""
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return [EARTH_SPEED * x for x in norm(cross(ECLIPTIC_POLE, [-x for x in sun]))]
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def stars_pleiades():
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# The Pleiades, right ascension 56.75 and declination 24.12 degrees, from
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# geostationary orbit, with the Sun behind the camera.
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ra, dec = math.radians(56.75), math.radians(24.12)
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look = [math.cos(dec) * math.cos(ra), math.cos(dec) * math.sin(ra), math.sin(dec)]
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camera = [GEO, 0.0, 0.0]
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sun = [-x for x in look]
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fmt = lambda v, d=2: "[" + ", ".join(f"{x:.{d}f}" for x in v) + "]"
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return f"""# A star field: the Pleiades through the example camera (12 by 7 degrees), from
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# geostationary orbit, long-exposed at 5 s. Stars are drawn at lighting L1 with camera
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# C1, from the catalog scripts/fetch-stars.py writes. Alcyone, the brightest at V 2.9,
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# gives about 200,000 electrons, ten times the full well; a V 8 star about 2,000 and a
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# V 11 star about 130. Generated by scripts/make-example-scenes.py.
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#
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# resolved render --scene examples/scenes/stars-pleiades.toml --lighting L1 --camera C1 --pretty --preview pleiades.png
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sun = {fmt([AU * x for x in sun], 0)}
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moon = [0, -384400000, 0]
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earth_velocity = {fmt(earth_velocity(sun))}
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[camera]
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exposure = 5
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[observer]
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position = {fmt(camera)}
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look_at = {fmt([camera[i] + 1e9 * look[i] for i in range(3)])}
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up = [0, 0, 1]
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velocity = [0.00, {GEO_SPEED:.2f}, 0.00]
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# At lighting L1, Earth's surface shows July (from scripts/fetch-earth.sh).
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[appearance]
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earth_month = 7
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"""
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def geo_telescope(range_m, phase_deg, f_number, exposure, description):
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# The camera at GEO_LONGITUDE on the geostationary arc, the target ahead along it.
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file, scale, center = "ssl1300.glb", 0.1, MODELS[3][3]
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lon = math.radians(GEO_LONGITUDE)
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camera = [GEO * math.cos(lon), GEO * math.sin(lon), 0.0]
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angle = lon + range_m / GEO
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spot = [GEO * math.cos(angle), GEO * math.sin(angle), 0.0]
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velocity = [-GEO_SPEED * math.sin(lon), GEO_SPEED * math.cos(lon), 0.0]
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look = norm([spot[i] - camera[i] for i in range(3)])
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image_up = [0.0, 0.0, 1.0]
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attitude = triad([1, 1, 1], [0, 0, 1], [-x for x in look], image_up)
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offset = mul(attitude, center)
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position = [spot[i] - offset[i] for i in range(3)]
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# The Sun `phase_deg` from the camera's direction as the target sees it, turned
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# about the image's up, 10 degrees out of the equator so the target is not shadowed
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# by Earth at any phase.
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back = [-x for x in look]
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side = cross(image_up, back)
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p, t = math.radians(phase_deg), math.radians(10.0)
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sun = norm([
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math.cos(t) * (math.cos(p) * back[i] + math.sin(p) * side[i]) + math.sin(t) * image_up[i]
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for i in range(3)
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])
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fmt = lambda v, d=2: "[" + ", ".join(f"{x:.{d}f}" for x in v) + "]"
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heading = textwrap.fill(description, 86, initial_indent="# ", subsequent_indent="# ")
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return f"""{heading}
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# A 1 m, f/{f_number:.0f} telescope ({100 / f_number:g} cm aperture, 5.5 urad per pixel, 0.6 by 0.34
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# degrees) on one geostationary satellite, imaging an SSL-1300 {range_m / 1000:.0f} km ahead along
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# the arc, lit at a phase of {phase_deg} degrees, against the stars toward the Milky Way in
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# Monoceros. Stars are drawn at lighting L1 with camera C1 (scripts/fetch-stars.py).
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# Generated by scripts/make-example-scenes.py; the model comes from
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# scripts/fetch-models.sh.
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#
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# resolved render --scene <this file> --lighting L1 --camera C1 --pretty --preview geo.png
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sun = {fmt([AU * x for x in sun], 0)}
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moon = [0, -384400000, 0]
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earth_velocity = {fmt(earth_velocity(sun))}
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[camera]
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focal_length = 1.0
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f_number = {f_number:.1f}
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exposure = {exposure}
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[observer]
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position = {fmt(camera)}
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look_at = {fmt(spot)}
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up = [0, 0, 1]
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velocity = {fmt(velocity)}
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# At lighting L1, Earth's surface shows July (from scripts/fetch-earth.sh), and lights
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# the target's Earth-facing side.
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[appearance]
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earth_month = 7
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[[target]]
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model = "../models/nasa/{file}"
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scale = {scale}
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position = {fmt(position, 4)}
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attitude = {fmt(quaternion(attitude), 9)}
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"""
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GEO_TELESCOPE = [
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("geo-telescope-100km", 100e3, 30, 8.0, 6e-4,
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"GEO to GEO at 100 km: the target about 55 px across, lit nearly face on, exposed "
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"short of saturating it, with only the brighter stars behind it."),
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("geo-telescope-100km-side", 100e3, 90, 8.0, 6e-4,
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"GEO to GEO at 100 km, lit from the side: half the target in shadow."),
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("geo-telescope-1000km", 1000e3, 30, 4.0, 0.2,
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"GEO to GEO at 1000 km, exposed 0.2 s at f/4 as a surveillance camera would: the "
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"target a few pixels across and far past saturation, in a field of stars to the "
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"catalog's limit, about V 15, which gives a few DN."),
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]
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out = pathlib.Path(__file__).resolve().parent.parent / "examples" / "scenes"
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for model in MODELS:
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path = out / f"{model[0]}.toml"
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@@ -458,3 +589,10 @@ print(f"wrote {path}")
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path = out / "moonrise.toml"
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path.write_text(moonrise())
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print(f"wrote {path}")
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path = out / "stars-pleiades.toml"
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path.write_text(stars_pleiades())
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print(f"wrote {path}")
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for name, range_m, phase, f_number, exposure, description in GEO_TELESCOPE:
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path = out / f"{name}.toml"
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path.write_text(geo_telescope(range_m, phase, f_number, exposure, description))
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print(f"wrote {path}")
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