Lucy
655f1c9af6
- orbital_elements.py: elliptical + hyperbolic orbit support - orbit_drawer.py: orbit point generation with SOI truncation - soi_calculator.py: SOI crossing time calculator - frame_transition.py: reference frame switching - test_orbital.py: 147 assertions, all passing - visual_test.py: pygame flyby visualization
78 lines
2.3 KiB
Python
78 lines
2.3 KiB
Python
"""
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Orbit trajectory point generation for rendering.
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generate_orbit_points() — full orbit (elliptical) or truncated
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hyperbolic path within a given cut-off radius.
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"""
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import math
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from typing import List, Optional, Tuple
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from orbital_elements import OrbitalElements, TAU
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def generate_orbit_points(
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orbit: OrbitalElements,
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num_points: int = 200,
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max_radius: Optional[float] = None,
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) -> List[Tuple[float, float]]:
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"""
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Generate *num_points* world-space positions along the orbit.
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Elliptical orbits → full closed loop, equally spaced in E.
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Hyperbolic orbits → samples H ∈ [−H_max, +H_max], truncated
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at *max_radius* (e.g. the planet's SOI edge).
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Parameters
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----------
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max_radius : float or None
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Only used for hyperbolic orbits. Points with r > max_radius
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are omitted. If None, samples out to r ≈ 5·|a| from focus.
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"""
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if orbit.is_hyperbolic:
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return _hyperbolic_points(orbit, num_points, max_radius)
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return _elliptical_points(orbit, num_points)
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def _elliptical_points(
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orbit: OrbitalElements, num_points: int,
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) -> List[Tuple[float, float]]:
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points = []
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for i in range(num_points):
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E = TAU * i / num_points
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points.append(orbit.position_from_E(E))
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return points
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def _hyperbolic_points(
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orbit: OrbitalElements,
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num_points: int,
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max_radius: Optional[float],
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) -> List[Tuple[float, float]]:
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"""
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Sample the hyperbolic branch that passes through periapsis.
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Truncates at *max_radius* by solving for the H values where
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r = max_radius, then sampling uniformly between those limits.
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"""
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r_limit = max_radius if max_radius is not None else 5.0 * abs(orbit.a)
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# Find H where r = r_limit.
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# r = |a|(e·cosh(H) − 1) → cosh(H) = (r/|a| + 1) / e
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abs_a = abs(orbit.a)
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cosh_Hmax = (r_limit / abs_a + 1.0) / orbit.e
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if cosh_Hmax < 1.0:
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return [] # entire orbit is outside the radius
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H_max = math.acosh(cosh_Hmax)
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points = []
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for i in range(num_points):
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frac = -1.0 + 2.0 * i / (num_points - 1) if num_points > 1 else 0.0
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H = frac * H_max
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x, y = orbit.position_from_H(H)
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r = math.hypot(x, y)
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if r <= r_limit + 1e-9:
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points.append((x, y))
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return points
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