From 47f156b88b92c905c108eb58e13979110b77ef6f Mon Sep 17 00:00:00 2001
From: cinnaboot <cinnaboot@protonmail.com>
Date: Sat, 31 Jan 2026 11:07:00 -0500
Subject: [PATCH] Add true anomaly validation for hyperbolic orbits in config
 validator
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New validation function validate_true_anomaly_ranges() checks that
hyperbolic orbits (e > 1) have true anomalies within physically valid
range: |ν| < arccos(-1/e)

This prevents configs from specifying starting positions that would
cause negative radius values (1 + e·cos(ν) ≤ 0).
---
 src/config_validator.cpp | 60 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/src/config_validator.cpp b/src/config_validator.cpp
index 48ea67b..500524b 100644
--- a/src/config_validator.cpp
+++ b/src/config_validator.cpp
@@ -200,6 +200,62 @@ bool validate_nested_orbits(SimulationState* sim) {
     return true;
 }
 
+bool validate_true_anomaly_ranges(SimulationState* sim) {
+    for (int i = 0; i < sim->body_count; i++) {
+        CelestialBody* body = &sim->bodies[i];
+
+        if (body->parent_index < 0) {
+            continue;
+        }
+
+        double e = body->orbit.eccentricity;
+        double nu = body->orbit.true_anomaly;
+
+        // Normalize nu to [0, 2π]
+        while (nu < 0.0) nu += 2.0 * M_PI;
+        while (nu >= 2.0 * M_PI) nu -= 2.0 * M_PI;
+
+        // Check hyperbolic orbit anomaly limits
+        if (e > 1.0) {
+            double max_nu = acos(-1.0 / e);
+            if (nu > max_nu && nu < (2.0 * M_PI - max_nu)) {
+                printf("Error: Body '%s' has invalid true_anomaly for hyperbolic orbit\n",
+                       body->name);
+                printf("  Eccentricity: %.4f\n", e);
+                printf("  True anomaly: %.4f rad\n", nu);
+                printf("  Valid range: [0, %.4f] ∪ [%.4f, 2π]\n", max_nu, 2.0 * M_PI - max_nu);
+                return false;
+            }
+        }
+    }
+
+    for (int i = 0; i < sim->craft_count; i++) {
+        Spacecraft* craft = &sim->spacecraft[i];
+
+        double e = craft->orbit.eccentricity;
+        double nu = craft->orbit.true_anomaly;
+
+        // Normalize nu to [0, 2π]
+        while (nu < 0.0) nu += 2.0 * M_PI;
+        while (nu >= 2.0 * M_PI) nu -= 2.0 * M_PI;
+
+        // Check hyperbolic orbit anomaly limits
+        if (e > 1.0) {
+            double max_nu = acos(-1.0 / e);
+            if (nu > max_nu && nu < (2.0 * M_PI - max_nu)) {
+                printf("Error: Spacecraft '%s' has invalid true_anomaly for hyperbolic orbit\n",
+                       craft->name);
+                printf("  Eccentricity: %.4f\n", e);
+                printf("  True anomaly: %.4f rad\n", nu);
+                printf("  Valid range: [0, %.4f] ∪ [%.4f, 2π]\n", max_nu, 2.0 * M_PI - max_nu);
+                return false;
+            }
+        }
+    }
+
+    return true;
+}
+
 bool validate_initial_positions(SimulationState* sim) {
     for (int i = 0; i < sim->body_count; i++) {
         CelestialBody* body = &sim->bodies[i];
@@ -249,6 +305,10 @@ bool run_all_config_validations(SimulationState* sim) {
         return false;
     }
 
+    if (!validate_true_anomaly_ranges(sim)) {
+        return false;
+    }
+
     if (!validate_mass_ratios(sim)) {
         return false;
     }