smooth out engine volume, fixing audio glitches

src/actor.rs

@@ -152,7 +152,7 @@ pub struct Engine {
     pub reaction_wheels: f32,
     pub engine_type: EngineType,
     pub warmup_seconds: f32,
-    pub current_warmup: f32,
+    pub current_warmup: f32, // between 0.0 and 1.0
 }
 impl Default for Engine {
     fn default() -> Self {

src/audio.rs

@@ -79,6 +79,7 @@ pub fn setup(
             source: asset_server.load(ASSET_THRUSTER),
             settings: PlaybackSettings {
                 mode: PlaybackMode::Loop,
+                volume: Volume::new(0.0),
                 paused: true,
                 ..default()
             },
@@ -90,6 +91,7 @@ pub fn setup(
             source: asset_server.load(ASSET_ROCKET),
             settings: PlaybackSettings {
                 mode: PlaybackMode::Loop,
+                volume: Volume::new(0.0),
                 paused: true,
                 ..default()
             },
@@ -101,6 +103,7 @@ pub fn setup(
             source: asset_server.load(ASSET_ION),
             settings: PlaybackSettings {
                 mode: PlaybackMode::Loop,
+                volume: Volume::new(0.0),
                 paused: true,
                 ..default()
             },

src/camera.rs

@@ -350,25 +350,39 @@ pub fn apply_input_to_player(
                 }
             }
         }
-        if let Ok(sink) = thruster_sound_controller.get_single() {
+        let sinks = vec![
-            if play_thruster_sound && !settings.mute_sfx && engine.engine_type == actor::EngineType::Monopropellant {
+            (1.2, actor::EngineType::Monopropellant, thruster_sound_controller.get_single()),
-                sink.play()
+            (1.0, actor::EngineType::Rocket, rocket_sound_controller.get_single()),
+            (1.4, actor::EngineType::Ion, ion_sound_controller.get_single()),
+        ];
+        let seconds_to_max_vol = 0.05;
+        let seconds_to_min_vol = 0.05;
+        for sink_data in sinks {
+            if let (vol_boost, engine_type, Ok(sink)) = sink_data {
+                if settings.mute_sfx {
+                    sink.pause();
+                }
+                else {
+                    let volume = sink.volume();
+                    if engine.engine_type == engine_type {
+                        if play_thruster_sound {
+                            sink.play();
+                            if volume < 1.0 {
+                                let maxvol = vol_boost;
+                                //let maxvol = engine.current_warmup * vol_boost;
+                                sink.set_volume((volume + dt / seconds_to_max_vol).clamp(0.0, maxvol));
+                            }
                         } else {
-                sink.pause()
+                            sink.set_volume((volume - dt / seconds_to_min_vol).clamp(0.0, 1.0));
                         }
                     }
-        if let Ok(sink) = rocket_sound_controller.get_single() {
+                    else if volume > 0.0 {
-            if play_thruster_sound && !settings.mute_sfx && engine.engine_type == actor::EngineType::Rocket {
+                        sink.set_volume((volume - dt / seconds_to_min_vol).clamp(0.0, 1.0));
-                sink.play()
+                    }
-            } else {
+                    if volume < 0.0001 {
-                sink.pause()
+                        sink.pause();
                     }
                 }
-        if let Ok(sink) = ion_sound_controller.get_single() {
-            if play_thruster_sound && !settings.mute_sfx && engine.engine_type == actor::EngineType::Ion {
-                sink.play()
-            } else {
-                sink.pause()
             }
         }
     }