From 3caea942e5321003584072f7fe1dfa7a330f0876 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20B=C3=B6klin?= <ludvig.boklin@protonmail.com>
Date: Thu, 3 Jun 2021 14:02:34 +0200
Subject: [PATCH] Interpolate fluid velocity updates to entities

---
 server/src/sys/windsim.rs | 19 ++++++++++---------
 server/src/windsim/mod.rs |  3 +--
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/server/src/sys/windsim.rs b/server/src/sys/windsim.rs
index dd44550260..b3e62178ee 100644
--- a/server/src/sys/windsim.rs
+++ b/server/src/sys/windsim.rs
@@ -1,5 +1,5 @@
 #![allow(dead_code)]
-use crate::windsim::WindSim;
+use crate::windsim::{WindSim, TPS};
 use common::{
     comp::{Fluid, PhysicsState, Pos, Vel},
     resources::DeltaTime,
@@ -53,15 +53,16 @@ impl<'a> System<'a> for Sys {
         windsim.tick(wind_sources, &dt);
 
         for (pos, physics_state) in (&positions, &mut physics_states).join() {
-            physics_state.in_fluid = physics_state
-                .in_fluid
-                .filter(|fluid| !matches!(fluid, Fluid::Air { .. }))
-                .or_else(|| {
-                    Some(Fluid::Air {
-                        elevation: pos.0.z,
-                        vel: Vel(windsim.get_velocity(*pos)),
-                    })
+            if let Fluid::Air { vel, elevation } = physics_state.in_fluid.unwrap_or_default() {
+                physics_state.in_fluid = Some(Fluid::Air {
+                    vel: Vel(Lerp::lerp(
+                        vel.0,
+                        windsim.get_velocity(*pos),
+                        inline_tweak::tweak!(0.5) / TPS as f32,
+                    )),
+                    elevation,
                 });
+            }
         }
     }
 }
diff --git a/server/src/windsim/mod.rs b/server/src/windsim/mod.rs
index c4d4a63006..74938ff9bd 100644
--- a/server/src/windsim/mod.rs
+++ b/server/src/windsim/mod.rs
@@ -10,7 +10,6 @@ use common::{
     comp::{Pos, Vel},
     resources::DeltaTime,
 };
-//use common_state::State;
 
 pub const DEFAULT_POS: Vec3<usize> = Vec3 { x: 0, y: 0, z: 0 };
 pub const GRID_SIZE: Vec3<usize> = Vec3 {
@@ -18,7 +17,7 @@ pub const GRID_SIZE: Vec3<usize> = Vec3 {
     y: Y_SIZE,
     z: Z_SIZE,
 };
-const TPS: u32 = 5;
+pub const TPS: u32 = 5;
 
 #[derive(Default)]
 pub struct WindSim {