fix rendering issue with begin/end frame functions

src/main.cpp

@@ -100,13 +100,15 @@ void run_gui_simulation(SimulationState* sim) {
 
         update_camera(&render_state, sim);
 
-        render_simulation(sim, &render_state);
-
-        // Render UI panels
-        render_info(sim);
-        render_body_list_ui(sim, &render_state, &ui_state);
-        render_body_info_ui(sim, &render_state);
-        render_maneuver_list_ui(sim, &render_state);
+        begin_frame();
+            render_simulation(sim, &render_state);
+
+            // Render UI panels
+            render_info(sim);
+            render_body_list_ui(sim, &render_state, &ui_state);
+            render_body_info_ui(sim, &render_state);
+            render_maneuver_list_ui(sim, &render_state);
+        end_frame();
     }
 
     close_renderer(&render_state);

src/renderer.cpp

@@ -527,11 +527,17 @@ void render_orbit(CelestialBody* body, CelestialBody* parent, RenderState* rende
     }
 }
 
-// Render the entire simulation
-void render_simulation(SimulationState* sim, RenderState* render_state) {
+void begin_frame() {
     BeginDrawing();
     ClearBackground(BLACK);
+}
+
+void end_frame() {
+    EndDrawing();
+}
 
+// Render the entire simulation
+void render_simulation(SimulationState* sim, RenderState* render_state) {
     BeginMode3D(render_state->camera);
 
     // Draw a subtle reference grid
@@ -576,6 +582,4 @@ void render_simulation(SimulationState* sim, RenderState* render_state) {
             render_maneuver_marker_screen_space(craft, maneuver, render_state);
         }
     }
-
-    EndDrawing();
 }

src/renderer.h

@@ -45,7 +45,10 @@ void update_camera(RenderState* render_state, SimulationState* sim);
 void render_body(CelestialBody* body, RenderState* render_state);
 void render_spacecraft_screen_space(Spacecraft* craft, RenderState* render_state);
 void render_maneuver_marker_screen_space(Spacecraft* craft, Maneuver* maneuver, RenderState* render_state);
+// NOTE: needs to be called between begin_frame() and end_frame()
 void render_simulation(SimulationState* sim, RenderState* render_state);
+void begin_frame();
+void end_frame();
 
 // Scaling functions
 Vector3 scale_position(Vec3 pos, double scale);