Fix orbit rendering to use local_velocity for nested orbits

src/renderer.cpp

@@ -301,7 +301,8 @@ void render_orbit(CelestialBody* body, CelestialBody* parent, RenderState* rende
 
     Vec3 r_vec = vec3_sub(body->position, parent->position);
     double r = vec3_magnitude(r_vec);
-    double v = vec3_magnitude(body->velocity);
+    Vec3 v_vec = body->local_velocity;
+    double v = vec3_magnitude(v_vec);
 
     if (r < 1.0) return;
 
@@ -309,11 +310,11 @@ void render_orbit(CelestialBody* body, CelestialBody* parent, RenderState* rende
     double specific_energy = (v * v) / 2.0 - mu / r;
 
     double v_squared = v * v;
-    double r_dot_v = r_vec.x * body->velocity.x + r_vec.y * body->velocity.y + r_vec.z * body->velocity.z;
+    double r_dot_v = r_vec.x * v_vec.x + r_vec.y * v_vec.y + r_vec.z * v_vec.z;
     Vec3 e_vec = {
-        (v_squared - mu / r) * r_vec.x - r_dot_v * body->velocity.x,
+        (v_squared - mu / r) * r_vec.x - r_dot_v * v_vec.x,
-        (v_squared - mu / r) * r_vec.y - r_dot_v * body->velocity.y,
+        (v_squared - mu / r) * r_vec.y - r_dot_v * v_vec.y,
-        (v_squared - mu / r) * r_vec.z - r_dot_v * body->velocity.z
+        (v_squared - mu / r) * r_vec.z - r_dot_v * v_vec.z
     };
     double e = vec3_magnitude(e_vec) / mu;
 
@@ -324,7 +325,7 @@ void render_orbit(CelestialBody* body, CelestialBody* parent, RenderState* rende
         128
     };
 
-    OrbitalBasis basis = calculate_orbital_basis(r_vec, body->velocity, e_vec);
+    OrbitalBasis basis = calculate_orbital_basis(r_vec, v_vec, e_vec);
 
     if (e < 0.98) {
         double a = -mu / (2.0 * specific_energy);
@@ -340,9 +341,9 @@ void render_orbit(CelestialBody* body, CelestialBody* parent, RenderState* rende
         render_hyperbolic_orbit(p, e, basis, parent->position, render_state, orbit_color);
     } else {
         Vec3 h_vec = {
-            r_vec.y * body->velocity.z - r_vec.z * body->velocity.y,
+            r_vec.y * v_vec.z - r_vec.z * v_vec.y,
-            r_vec.z * body->velocity.x - r_vec.x * body->velocity.z,
+            r_vec.z * v_vec.x - r_vec.x * v_vec.z,
-            r_vec.x * body->velocity.y - r_vec.y * body->velocity.x
+            r_vec.x * v_vec.y - r_vec.y * v_vec.x
         };
         double h_squared = h_vec.x * h_vec.x + h_vec.y * h_vec.y + h_vec.z * h_vec.z;
         double p = h_squared / mu;