Add machinery for storing component buffers for interpolation.

Cargo.lock

@@ -5619,6 +5619,7 @@ dependencies = [
  "hashbrown",
  "serde",
  "specs",
+ "specs-idvs",
  "sum_type",
  "tracing",
  "vek 0.14.1",

common/net/Cargo.toml

@@ -25,6 +25,7 @@ authc = { git = "https://gitlab.com/veloren/auth.git", rev = "fb3dcbc4962b367253
 
 # ECS
 specs = { git = "https://github.com/amethyst/specs.git", features = ["serde", "storage-event-control"], rev = "5a9b71035007be0e3574f35184acac1cd4530496" }
+specs-idvs = { git = "https://gitlab.com/veloren/specs-idvs.git", rev = "b65fb220e94f5d3c9bc30074a076149763795556" }
 
 # Serde
-serde = { version = "1.0.110", features = ["derive"] }
+serde = { version = "1.0.110", features = ["derive"] }

common/net/src/msg/ecs_packet.rs

@@ -100,7 +100,7 @@ impl sync::CompPacket for EcsCompPacket {
             EcsCompPacket::Gravity(comp) => sync::handle_insert(comp, entity, world),
             EcsCompPacket::Sticky(comp) => sync::handle_insert(comp, entity, world),
             EcsCompPacket::CharacterState(comp) => sync::handle_insert(comp, entity, world),
-            EcsCompPacket::Pos(comp) => sync::handle_insert(comp, entity, world),
+            EcsCompPacket::Pos(comp) => sync::handle_interp_insert(comp, entity, world),
             EcsCompPacket::Vel(comp) => sync::handle_insert(comp, entity, world),
             EcsCompPacket::Ori(comp) => sync::handle_insert(comp, entity, world),
             EcsCompPacket::Shockwave(comp) => sync::handle_insert(comp, entity, world),
@@ -132,7 +132,7 @@ impl sync::CompPacket for EcsCompPacket {
             EcsCompPacket::Gravity(comp) => sync::handle_modify(comp, entity, world),
             EcsCompPacket::Sticky(comp) => sync::handle_modify(comp, entity, world),
             EcsCompPacket::CharacterState(comp) => sync::handle_modify(comp, entity, world),
-            EcsCompPacket::Pos(comp) => sync::handle_modify(comp, entity, world),
+            EcsCompPacket::Pos(comp) => sync::handle_interp_modify(comp, entity, world),
             EcsCompPacket::Vel(comp) => sync::handle_modify(comp, entity, world),
             EcsCompPacket::Ori(comp) => sync::handle_modify(comp, entity, world),
             EcsCompPacket::Shockwave(comp) => sync::handle_modify(comp, entity, world),
@@ -168,7 +168,7 @@ impl sync::CompPacket for EcsCompPacket {
             EcsCompPhantom::CharacterState(_) => {
                 sync::handle_remove::<comp::CharacterState>(entity, world)
             },
-            EcsCompPhantom::Pos(_) => sync::handle_remove::<comp::Pos>(entity, world),
+            EcsCompPhantom::Pos(_) => sync::handle_interp_remove::<comp::Pos>(entity, world),
             EcsCompPhantom::Vel(_) => sync::handle_remove::<comp::Vel>(entity, world),
             EcsCompPhantom::Ori(_) => sync::handle_remove::<comp::Ori>(entity, world),
             EcsCompPhantom::Shockwave(_) => sync::handle_remove::<comp::Shockwave>(entity, world),

common/net/src/sync/interpolation.rs

@@ -0,0 +1,26 @@
+// impls of `InterpolatableComponent` on things defined in `common`, since `common_net` is
+// downstream of `common`
+use common::comp::{Pos, Vel};
+use super::InterpolatableComponent;
+use specs::{Component, Entity, World};
+use specs_idvs::IdvStorage;
+use vek::Vec3;
+
+#[derive(Default)]
+pub struct PosBuffer(pub [Vec3<f32>; 4]);
+
+impl Component for PosBuffer {
+    type Storage = IdvStorage<Self>;
+}
+
+impl InterpolatableComponent for Pos {
+    type InterpData = PosBuffer;
+
+    fn interpolate(self, data: &mut Self::InterpData, entity: Entity, world: &World) -> Self {
+        for i in 0..data.0.len()-1 {
+            data.0[i] = data.0[i+1];
+        }
+        data.0[data.0.len()-1] = self.0;
+        self
+    }
+}

common/net/src/sync/mod.rs

@@ -1,5 +1,6 @@
 // Note: Currently only one-way sync is supported until a usecase for two-way
 // sync arises
+pub mod interpolation;
 mod packet;
 mod sync_ext;
 mod track;
@@ -7,8 +8,9 @@ mod track;
 // Reexports
 pub use common::uid::{Uid, UidAllocator};
 pub use packet::{
-    handle_insert, handle_modify, handle_remove, CompPacket, CompSyncPackage, EntityPackage,
-    EntitySyncPackage, StatePackage,
+    handle_insert, handle_interp_insert, handle_interp_modify, handle_interp_remove, handle_modify,
+    handle_remove, CompPacket, CompSyncPackage, EntityPackage, EntitySyncPackage,
+    InterpolatableComponent, StatePackage,
 };
 pub use sync_ext::WorldSyncExt;
 pub use track::UpdateTracker;

common/net/src/sync/packet.rs

@@ -42,6 +42,40 @@ pub fn handle_remove<C: Component>(entity: Entity, world: &World) {
     world.write_storage::<C>().remove(entity);
 }
 
+pub trait InterpolatableComponent: Component {
+    type InterpData: Component + Default;
+
+    fn interpolate(self, data: &mut Self::InterpData, entity: Entity, world: &World) -> Self;
+}
+
+pub fn handle_interp_insert<C: InterpolatableComponent>(comp: C, entity: Entity, world: &World) {
+    let mut interp_data = C::InterpData::default();
+    let comp = comp.interpolate(&mut interp_data, entity, world);
+    handle_insert(comp, entity, world);
+    handle_insert(interp_data, entity, world);
+}
+
+pub fn handle_interp_modify<C: InterpolatableComponent + Debug>(
+    comp: C,
+    entity: Entity,
+    world: &World,
+) {
+    if let Some(mut interp_data) = world.write_storage::<C::InterpData>().get_mut(entity) {
+        let comp = comp.interpolate(&mut interp_data, entity, world);
+        handle_modify(comp, entity, world);
+    } else {
+        error!(
+            ?comp,
+            "Error modifying interpolation data for synced component, it doesn't seem to exist"
+        );
+    }
+}
+
+pub fn handle_interp_remove<C: InterpolatableComponent>(entity: Entity, world: &World) {
+    handle_remove::<C>(entity, world);
+    handle_remove::<C::InterpData>(entity, world);
+}
+
 #[derive(Copy, Clone, Debug, Serialize, Deserialize)]
 pub enum CompUpdateKind<P: CompPacket> {
     Inserted(P),

common/sys/src/state.rs

@@ -15,7 +15,7 @@ use common::{
 };
 use common_base::span;
 use common_ecs::{PhysicsMetrics, SysMetrics};
-use common_net::sync::WorldSyncExt;
+use common_net::sync::{interpolation, WorldSyncExt};
 use hashbrown::{HashMap, HashSet};
 use rayon::{ThreadPool, ThreadPoolBuilder};
 use specs::{
@@ -164,6 +164,7 @@ impl State {
         // Register client-local components
         // TODO: only register on the client
         ecs.register::<comp::LightAnimation>();
+        ecs.register::<interpolation::PosBuffer>();
 
         // Register server-local components
         // TODO: only register on the server