fix(client_core): 🐛 Cap prediction to avoid head and controllers flying off

alvr/client_core/src/connection.rs

@@ -70,6 +70,7 @@ pub struct ConnectionContext {
     pub view_params: RwLock<[ViewParams; 2]>,
     pub uses_multimodal_protocol: RelaxedAtomic,
     pub velocities_multiplier: RwLock<f32>,
+    pub max_prediction: RwLock<Duration>,
 }
 
 fn set_hud_message(event_queue: &Mutex<VecDeque<ClientCoreEvent>>, message: &str) {
@@ -205,6 +206,7 @@ fn connection_pipeline(
     let negotiated_config = stream_config.negotiated_config;
 
     *ctx.velocities_multiplier.write() = settings.extra.velocities_multiplier;
+    *ctx.max_prediction.write() = Duration::from_millis(settings.headset.max_prediction_ms);
 
     *ctx.statistics_manager.lock() = Some(StatisticsManager::new(
         settings.connection.statistics_history_size,

alvr/client_core/src/lib.rs

@@ -234,12 +234,15 @@ impl ClientCoreContext {
     ) {
         dbg_client_core!("send_tracking");
 
-        let target_timestamp =
-            if let Some(stats) = &*self.connection_context.statistics_manager.lock() {
-                poll_timestamp + stats.average_total_pipeline_latency()
-            } else {
-                poll_timestamp
-            };
+        let max_prediction = *self.connection_context.max_prediction.read();
+
+        let target_timestamp = if let Some(stats) =
+            &*self.connection_context.statistics_manager.lock()
+        {
+            poll_timestamp + Duration::max(stats.average_total_pipeline_latency(), max_prediction)
+        } else {
+            poll_timestamp
+        };
 
         for (id, motion) in &mut device_motions {
             let velocity_multiplier = *self.connection_context.velocities_multiplier.read();
@@ -262,7 +265,8 @@ impl ClientCoreContext {
                 motion.linear_velocity = Vec3::ZERO;
                 motion.angular_velocity = Vec3::ZERO;
             } else if let Some(stats) = &*self.connection_context.statistics_manager.lock() {
-                let tracker_timestamp = poll_timestamp + stats.tracker_prediction_offset();
+                let tracker_timestamp = poll_timestamp
+                    + Duration::max(stats.tracker_prediction_offset(), max_prediction);
 
                 *motion = motion.predict(poll_timestamp, tracker_timestamp);
             }

alvr/session/src/settings.rs

@@ -1109,6 +1109,13 @@ Tilted: the world gets tilted when long pressing the oculus button. This is usef
     #[schema(flag = "steamvr-restart")]
     #[schema(strings(display_name = "VMC"))]
     pub vmc: Switch<VMCConfig>,
+
+    #[schema(strings(
+        help = "Maximum prediction for head and controllers. Used to avoid too much jitter during loading."
+    ))]
+    #[schema(flag = "real-time")]
+    #[schema(gui(slider(min = 0, max = 200, step = 5)), suffix = "ms")]
+    pub max_prediction_ms: u64,
 }
 
 #[derive(SettingsSchema, Serialize, Deserialize, Clone, Copy)]
@@ -1823,6 +1830,7 @@ pub fn session_settings_default() -> SettingsDefault {
             rotation_recentering_mode: RotationRecenteringModeDefault {
                 variant: RotationRecenteringModeDefaultVariant::Yaw,
             },
+            max_prediction_ms: 100,
         },
         connection: ConnectionConfigDefault {
             stream_protocol: SocketProtocolDefault {