From c6e0292d030fc57596f55ae3eddfbcf91dfdc331 Mon Sep 17 00:00:00 2001
From: Anuken <arnukren@gmail.com>
Date: Sat, 26 Jun 2021 09:52:03 -0400
Subject: [PATCH] Fixed clientside physics jitter

---
 core/src/mindustry/async/PhysicsProcess.java | 16 +++++++++++++---
 gradle.properties                            |  2 +-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/core/src/mindustry/async/PhysicsProcess.java b/core/src/mindustry/async/PhysicsProcess.java
index a7b17a5ffc..c8594a3ee2 100644
--- a/core/src/mindustry/async/PhysicsProcess.java
+++ b/core/src/mindustry/async/PhysicsProcess.java
@@ -24,6 +24,7 @@ public class PhysicsProcess implements AsyncProcess{
     @Override
     public void begin(){
         if(physics == null) return;
+        boolean local = !Vars.net.client();
 
         //remove stale entities
         refs.removeAll(ref -> {
@@ -62,6 +63,7 @@ public class PhysicsProcess implements AsyncProcess{
                 entity.isGrounded() ? layerGround : layerFlying;
             ref.x = entity.x;
             ref.y = entity.y;
+            ref.body.local = local || entity.isLocal();
         }
     }
 
@@ -156,6 +158,10 @@ public class PhysicsProcess implements AsyncProcess{
 
             for(int i = 0; i < bodies.size; i++){
                 PhysicsBody body = bodies.items[i];
+
+                //for clients, the only body that collides is the local one; all other physics simulations are handled by the server.
+                if(!body.local) continue;
+
                 body.hitbox(rect);
 
                 seq.size = 0;
@@ -174,10 +180,14 @@ public class PhysicsProcess implements AsyncProcess{
                         float ms = body.mass + other.mass;
                         float m1 = other.mass / ms, m2 = body.mass / ms;
 
+                        //first body is always local due to guard check above
                         body.x += vec.x * m1 / scl;
                         body.y += vec.y * m1 / scl;
-                        other.x -= vec.x * m2 / scl;
-                        other.y -= vec.y * m2 / scl;
+
+                        if(other.local){
+                            other.x -= vec.x * m2 / scl;
+                            other.y -= vec.y * m2 / scl;
+                        }
                     }
                 }
                 body.collided = true;
@@ -187,7 +197,7 @@ public class PhysicsProcess implements AsyncProcess{
         public static class PhysicsBody implements QuadTreeObject{
             public float x, y, radius, mass;
             public int layer = 0;
-            public boolean collided = false;
+            public boolean collided = false, local = true;
 
             @Override
             public void hitbox(Rect out){
diff --git a/gradle.properties b/gradle.properties
index 381b7069d4..9c7d434b68 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -10,4 +10,4 @@ kapt.include.compile.classpath=false
 kotlin.stdlib.default.dependency=false
 #needed for android compilation
 android.useAndroidX=true
-archash=45d17a1ade5b67b1e663785592d25f833feeecaf
+archash=1dd6c22dad3981525760254900e91634e7513714