Add lerping of physics to extrapolated position, and enable sending updates for stopped entities.

common/net/src/sync/interpolation.rs

@@ -14,22 +14,31 @@ pub struct InterpBuffer<T> {
     pub i: usize,
 }
 
+impl<T> InterpBuffer<T> {
+    fn push(&mut self, time: f64, x: T) {
+        let InterpBuffer {
+            ref mut buf,
+            ref mut i,
+        } = self;
+        *i += 1;
+        *i %= buf.len();
+        buf[*i] = (time, x);
+    }
+}
+
 impl<T: 'static + Send + Sync> Component for InterpBuffer<T> {
     type Storage = IdvStorage<Self>;
 }
 
+// 0 is pure physics, 1 is pure extrapolation
+const PHYSICS_VS_EXTRAPOLATION_FACTOR: f32 = 0.2;
+
 impl InterpolatableComponent for Pos {
     type InterpData = InterpBuffer<Pos>;
     type ReadData = Vel;
 
     fn update_component(&self, interp_data: &mut Self::InterpData, time: f64) {
-        let InterpBuffer {
+        interp_data.push(time, *self);
-            ref mut buf,
-            ref mut i,
-        } = interp_data;
-        *i += 1;
-        *i %= buf.len();
-        buf[*i] = (time, *self);
     }
 
     fn interpolate(self, interp_data: &Self::InterpData, t2: f64, _vel: &Vel) -> Self {
@@ -50,7 +59,7 @@ impl InterpolatableComponent for Pos {
             out = p1.0;
         }
 
-        Pos(out)
+        Pos(Lerp::lerp(self.0, out, PHYSICS_VS_EXTRAPOLATION_FACTOR))
     }
 }
 
@@ -59,13 +68,7 @@ impl InterpolatableComponent for Vel {
     type ReadData = ();
 
     fn update_component(&self, interp_data: &mut Self::InterpData, time: f64) {
-        let InterpBuffer {
+        interp_data.push(time, *self);
-            ref mut buf,
-            ref mut i,
-        } = interp_data;
-        *i += 1;
-        *i %= buf.len();
-        buf[*i] = (time, *self);
     }
 
     fn interpolate(self, interp_data: &Self::InterpData, t2: f64, _: &()) -> Self {
@@ -85,7 +88,7 @@ impl InterpolatableComponent for Vel {
             out = p1.0;
         }
 
-        Vel(out)
+        Vel(Lerp::lerp(self.0, out, PHYSICS_VS_EXTRAPOLATION_FACTOR))
     }
 }
 
@@ -94,13 +97,7 @@ impl InterpolatableComponent for Ori {
     type ReadData = ();
 
     fn update_component(&self, interp_data: &mut Self::InterpData, time: f64) {
-        let InterpBuffer {
+        interp_data.push(time, *self);
-            ref mut buf,
-            ref mut i,
-        } = interp_data;
-        *i += 1;
-        *i %= buf.len();
-        buf[*i] = (time, *self);
     }
 
     fn interpolate(self, interp_data: &Self::InterpData, t2: f64, _: &()) -> Self {
@@ -120,6 +117,6 @@ impl InterpolatableComponent for Ori {
             out = p1.0;
         }
 
-        Ori(out.normalized())
+        Ori(Slerp::slerp(self.0, out, PHYSICS_VS_EXTRAPOLATION_FACTOR).normalized())
     }
 }

server/src/sys/entity_sync.rs

@@ -249,9 +249,18 @@ impl<'a> System<'a> for Sys {
             {
                 let mut comp_sync_package = CompSyncPackage::new();
                 let mut throttle = true;
+
+                // extrapolation depends on receiving several frames indicating that something
+                // has stopped in order for the extrapolated value to have
+                // stopped
+                const SEND_UNCHANGED_PHYSICS_DATA: bool = true;
+
                 // TODO: An entity that stopped moving on a tick that it wasn't sent to the
                 // player will never have its position updated
-                match last_pos.get(entity).map(|&l| l.0 != pos) {
+                match last_pos
+                    .get(entity)
+                    .map(|&l| l.0 != pos || SEND_UNCHANGED_PHYSICS_DATA)
+                {
                     Some(false) => {},
                     Some(true) => {
                         let _ = last_pos.insert(entity, Last(pos));
@@ -265,7 +274,10 @@ impl<'a> System<'a> for Sys {
                 }
 
                 if let Some(&vel) = maybe_vel {
-                    match last_vel.get(entity).map(|&l| l.0 != vel) {
+                    match last_vel
+                        .get(entity)
+                        .map(|&l| l.0 != vel || SEND_UNCHANGED_PHYSICS_DATA)
+                    {
                         Some(false) => {},
                         Some(true) => {
                             let _ = last_vel.insert(entity, Last(vel));
@@ -286,7 +298,10 @@ impl<'a> System<'a> for Sys {
                 }
 
                 if let Some(&ori) = maybe_ori {
-                    match last_ori.get(entity).map(|&l| l.0 != ori) {
+                    match last_ori
+                        .get(entity)
+                        .map(|&l| l.0 != ori || SEND_UNCHANGED_PHYSICS_DATA)
+                    {
                         Some(false) => {},
                         Some(true) => {
                             let _ = last_ori.insert(entity, Last(ori));