Add American V8 preset, carb fuel transport, and adaptive desktop audio

include/FluidSim/OutdoorAudio.hpp

@@ -14,6 +14,8 @@ struct OutdoorAudioConfig {
     Vec3 listener_right{1.0f, 0.0f, 0.0f};
     Vec3 intake_position{-0.2f, 0.7f, 0.0f};
     Vec3 exhaust_position{0.55f, 0.5f, 0.0f};
+    Vec3 second_exhaust_position{-0.55f, 0.5f, 0.0f};
+    bool dual_exhaust{};
     float ear_spacing{0.18f}, sound_speed{343.0f};
     float ground_y{0.0f}, wall_x{-1.5f};
     float ground_reflection{0.35f}, wall_reflection{0.65f};
@@ -26,7 +28,7 @@ struct OutdoorAudioConfig {
 class OutdoorAudio {
 public:
     explicit OutdoorAudio(int sample_rate = 44100, OutdoorAudioConfig config = {});
-    AudioFrame process(float intake_mass_flow, float exhaust_mass_flow);
+    AudioFrame process(float intake_mass_flow, float exhaust_mass_flow, float second_exhaust_mass_flow = 0);
     void set_scene(OutdoorScene scene) { scene_ = scene; }
     OutdoorScene scene() const { return scene_; }
     void set_monitor_filter(bool enabled) { monitor_filter_ = enabled; } // Set before playback/capture.
@@ -60,7 +62,7 @@ private:
     OutdoorAudioConfig config_;
     OutdoorScene scene_{OutdoorScene::Wall};
     bool monitor_filter_{true};
-    std::array<Emitter, 2> emitters_;
+    std::array<Emitter, 3> emitters_;
     std::array<TailLine, 4> tail_;
     std::array<float, 4> weights_{1, 0, 0, 0};
     float scene_alpha_{}, tail_alpha_{}, tail_mix_{};