marss 0.0.3

Mars celestial simulation crate for the MilkyWay SolarSystem workspace
Documentation 
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pub struct DustSystemEndpoint {
    pub base_altitude_m: f64,
    pub top_altitude_m: f64,
    pub optical_depth: f64,
    pub single_scatter_albedo: f64,
    pub asymmetry_parameter: f64,
    pub particle_effective_radius_um: f64,
    pub color_linear: [f64; 3],
}

impl DustSystemEndpoint {
    pub fn mars_background() -> Self {
        Self {
            base_altitude_m: 0.0,
            top_altitude_m: 40_000.0,
            optical_depth: crate::MEAN_DUST_OPTICAL_DEPTH,
            single_scatter_albedo: 0.92,
            asymmetry_parameter: 0.63,
            particle_effective_radius_um: 1.5,
            color_linear: [0.72, 0.45, 0.20],
        }
    }

    pub fn mars_global_storm() -> Self {
        Self {
            base_altitude_m: 0.0,
            top_altitude_m: 80_000.0,
            optical_depth: crate::GLOBAL_STORM_OPTICAL_DEPTH,
            single_scatter_albedo: 0.94,
            asymmetry_parameter: 0.65,
            particle_effective_radius_um: 2.5,
            color_linear: [0.68, 0.40, 0.18],
        }
    }

    pub fn density_at_altitude(&self, alt_m: f64) -> f64 {
        if alt_m < self.base_altitude_m || alt_m > self.top_altitude_m {
            return 0.0;
        }
        let scale_h = (self.top_altitude_m - self.base_altitude_m) / 4.0;
        let h = alt_m - self.base_altitude_m;
        self.optical_depth * (-h / scale_h).exp()
    }

    pub fn surface_solar_fraction(&self) -> f64 {
        (-self.optical_depth).exp()
    }

    pub fn phase_function(&self, cos_theta: f64) -> f64 {
        let g = self.asymmetry_parameter;
        (1.0 - g * g) / (4.0 * std::f64::consts::PI * (1.0 + g * g - 2.0 * g * cos_theta).powf(1.5))
    }

    pub fn effective_radius_um(&self) -> f64 {
        self.particle_effective_radius_um
    }
}