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Refactor check_maneuver_trigger: extract helpers, fix near-circular orbit handling, add next-step detection

main
cinnaboot 5 months ago
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10ec5c7238
commit
db802f1983
1 changed files with 113 additions and 71 deletions
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  1. 184
      src/maneuver.cpp

184
src/maneuver.cpp
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@ -110,6 +110,85 @@ OrbitalElements preview_burn_result(const Spacecraft* craft, BurnDirection direc
return cartesian_to_orbital_elements(pos, new_vel, parent_mass);
}
static double normalize_angle(double angle) {
while (angle < 0.0) angle += 2.0 * M_PI;
while (angle >= 2.0 * M_PI) angle -= 2.0 * M_PI;
return angle;
}
static double angular_distance(double a, double b) {
double diff = fabs(normalize_angle(a) - normalize_angle(b));
return (diff > M_PI) ? (2.0 * M_PI - diff) : diff;
}
static bool angle_between(double current, double next, double target) {
double curr_norm = normalize_angle(current);
double next_norm = normalize_angle(next);
double target_norm = normalize_angle(target);
if (curr_norm <= next_norm) {
return (target_norm >= curr_norm) && (target_norm <= next_norm);
} else {
return (target_norm >= curr_norm) || (target_norm <= next_norm);
}
}
static double calculate_true_anomaly(Vec3 r, Vec3 v, Vec3 e_vec, double e_mag, double r_mag) {
// For near-circular orbits, eccentricity vector is near-zero
// Compute true anomaly as the angle in the orbital plane
if (e_mag < 1e-10) {
Vec3 h = vec3_cross(r, v);
double h_mag = vec3_magnitude(h);
if (h_mag < 1e-10) return 0.0;
// Create a coordinate system in the orbital plane
Vec3 z_hat = vec3_scale(h, 1.0 / h_mag);
// Choose x-axis as cross product of Z (world up) and orbit normal
// This gives a consistent reference direction in the orbital plane
Vec3 world_z = {0.0, 0.0, 1.0};
Vec3 x_hat = vec3_cross(world_z, z_hat);
double x_hat_mag = vec3_magnitude(x_hat);
if (x_hat_mag < 1e-10) {
// Orbit is equatorial, use world X as reference
x_hat = (Vec3){1.0, 0.0, 0.0};
} else {
x_hat = vec3_scale(x_hat, 1.0 / x_hat_mag);
}
Vec3 y_hat = vec3_cross(z_hat, x_hat);
// Project position onto this orbital plane coordinate system
double x_proj = vec3_dot(r, x_hat);
double y_proj = vec3_dot(r, y_hat);
// True anomaly is the angle in the orbital plane
double nu = atan2(y_proj, x_proj);
if (nu < 0) nu += 2.0 * M_PI;
return nu;
}
// Standard calculation using eccentricity vector
double cos_nu = vec3_dot(e_vec, r) / (e_mag * r_mag);
cos_nu = fmax(-1.0, fmin(1.0, cos_nu));
double nu = acos(cos_nu);
// Determine correct quadrant using cross product
Vec3 r_cross_v = vec3_cross(r, v);
double r_cross_v_dot_e = vec3_dot(r_cross_v, e_vec);
if (r_cross_v_dot_e < 0) {
nu = 2.0 * M_PI - nu;
}
return nu;
}
static Vec3 calculate_eccentricity_vector(Vec3 r, Vec3 v, Vec3 h, double mu) {
Vec3 v_cross_h = vec3_cross(v, h);
Vec3 v_cross_h_over_mu = vec3_scale(v_cross_h, 1.0 / mu);
double r_mag = vec3_magnitude(r);
Vec3 r_over_mag = vec3_scale(r, 1.0 / r_mag);
return vec3_sub(v_cross_h_over_mu, r_over_mag);
}
bool check_maneuver_trigger(Maneuver* maneuver, Spacecraft* craft, SimulationState* sim) {
switch (maneuver->trigger_type) {
case TRIGGER_TIME:
@ -118,87 +197,50 @@ bool check_maneuver_trigger(Maneuver* maneuver, Spacecraft* craft, SimulationSta
case TRIGGER_TRUE_ANOMALY: {
Vec3 r = craft->local_position;
Vec3 v = craft->local_velocity;
double r_mag = vec3_magnitude(r);
double v_mag = vec3_magnitude(v);
if (r_mag < 1.0) {
return false;
}
Vec3 r_unit = vec3_scale(r, 1.0 / r_mag);
// Validate position magnitude (avoid division by zero)
if (r_mag < 1.0) return false;
// Calculate angular momentum
Vec3 h = vec3_cross(r, v);
double h_mag = vec3_magnitude(h);
if (h_mag < 1e-10) return false; // Near-linear trajectory
if (h_mag < 1e-10) {
return false;
}
Vec3 e_vec = {0.0, 0.0, 0.0};
double mu = 0.0;
if (craft->parent_index >= 0 && craft->parent_index < sim->body_count) {
CelestialBody* parent = &sim->bodies[craft->parent_index];
mu = G * parent->mass;
Vec3 v_cross_h = vec3_cross(v, h);
Vec3 v_cross_h_over_mu = vec3_scale(v_cross_h, 1.0 / mu);
Vec3 r_over_mag = vec3_scale(r, 1.0 / r_mag);
e_vec = vec3_sub(v_cross_h_over_mu, r_over_mag);
} else {
// Get parent body for gravitational parameter
if (craft->parent_index < 0 || craft->parent_index >= sim->body_count) {
return false;
}
CelestialBody* parent = &sim->bodies[craft->parent_index];
double mu = G * parent->mass;
Vec3 e_vec = calculate_eccentricity_vector(r, v, h, mu);
double e_mag = vec3_magnitude(e_vec);
if (e_mag < 1e-10) {
Vec3 v_unit = vec3_scale(v, 1.0 / v_mag);
double cos_nu = vec3_dot(r_unit, v_unit);
cos_nu = fmax(-1.0, fmin(1.0, cos_nu));
double nu = acos(cos_nu);
double target_nu = maneuver->trigger_value;
while (target_nu < 0) target_nu += 2.0 * M_PI;
while (target_nu >= 2.0 * M_PI) target_nu -= 2.0 * M_PI;
double nu_normalized = nu;
while (nu_normalized < 0) nu_normalized += 2.0 * M_PI;
while (nu_normalized >= 2.0 * M_PI) nu_normalized -= 2.0 * M_PI;
double angle_diff = fabs(nu_normalized - target_nu);
if (angle_diff > M_PI) {
angle_diff = 2.0 * M_PI - angle_diff;
}
return angle_diff < 0.01;
}
double cos_nu = vec3_dot(e_vec, r) / (e_mag * r_mag);
cos_nu = fmax(-1.0, fmin(1.0, cos_nu));
double nu = acos(cos_nu);
Vec3 r_cross_v = vec3_cross(r, v);
double r_cross_v_dot_e = vec3_dot(r_cross_v, e_vec);
if (r_cross_v_dot_e < 0) {
nu = 2.0 * M_PI - nu;
}
double target_nu = maneuver->trigger_value;
while (target_nu < 0) target_nu += 2.0 * M_PI;
while (target_nu >= 2.0 * M_PI) target_nu -= 2.0 * M_PI;
double nu_normalized = nu;
while (nu_normalized < 0) nu_normalized += 2.0 * M_PI;
while (nu_normalized >= 2.0 * M_PI) nu_normalized -= 2.0 * M_PI;
double angle_diff = fabs(nu_normalized - target_nu);
if (angle_diff > M_PI) {
angle_diff = 2.0 * M_PI - angle_diff;
}
return angle_diff < 0.01;
double target_nu = normalize_angle(maneuver->trigger_value);
double current_nu = calculate_true_anomaly(r, v, e_vec, e_mag, r_mag);
double current_nu_norm = normalize_angle(current_nu);
double current_diff = angular_distance(current_nu_norm, target_nu);
if (current_diff < 0.01) return true;
// Propagate orbit forward by one time step to check if we'll cross trigger
OrbitalElements future_elements = propagate_orbital_elements(craft->orbit, sim->dt, parent->mass);
Vec3 future_r, future_v;
orbital_elements_to_cartesian(future_elements, parent->mass, &future_r, &future_v);
double future_r_mag = vec3_magnitude(future_r);
if (future_r_mag < 1.0) return false;
// Calculate future eccentricity vector for true anomaly calculation
Vec3 future_h = vec3_cross(future_r, future_v);
Vec3 future_e_vec = calculate_eccentricity_vector(future_r, future_v, future_h, mu);
double future_e_mag = vec3_magnitude(future_e_vec);
// Calculate future true anomaly
double future_nu = calculate_true_anomaly(future_r, future_v, future_e_vec, future_e_mag, future_r_mag);
double future_nu_norm = normalize_angle(future_nu);
// Check if target lies between current and future positions
return angle_between(current_nu_norm, future_nu_norm, target_nu);
}
default:

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