From d1f1c1907a7ce763d7742b2a8edf6f940b4c22d3 Mon Sep 17 00:00:00 2001
From: liabru <liabru@brm.io>
Date: Tue, 10 Mar 2020 08:48:42 +0000
Subject: [PATCH] Revert "Merge branch 'pr/527'"

This reverts commit 4df048da79d5fc0e112096418ad6aa6097197eef, reversing
changes made to 52f3734b3e9f2ddb956641baadd5aedbfa62b8ed.
---
 src/body/Body.js          |  1 -
 src/collision/Resolver.js | 68 ++++++++++++++++++---------------------
 src/core/Engine.js        |  2 +-
 3 files changed, 32 insertions(+), 39 deletions(-)

diff --git a/src/body/Body.js b/src/body/Body.js
index 9c39195..f38d2c8 100644
--- a/src/body/Body.js
+++ b/src/body/Body.js
@@ -49,7 +49,6 @@ var Axes = require('../geometry/Axes');
             force: { x: 0, y: 0 },
             torque: 0,
             positionImpulse: { x: 0, y: 0 },
-            previousPositionImpulse: { x: 0, y: 0 },
             constraintImpulse: { x: 0, y: 0, angle: 0 },
             totalContacts: 0,
             speed: 0,
diff --git a/src/collision/Resolver.js b/src/collision/Resolver.js
index 37c9692..c53817f 100644
--- a/src/collision/Resolver.js
+++ b/src/collision/Resolver.js
@@ -48,33 +48,23 @@ var Bounds = require('../geometry/Bounds');
      * Find a solution for pair positions.
      * @method solvePosition
      * @param {pair[]} pairs
-     * @param {body[]} bodies
      * @param {number} timeScale
      */
-    Resolver.solvePosition = function(pairs, bodies, timeScale) {
+    Resolver.solvePosition = function(pairs, timeScale) {
         var i,
-            normalX,
-            normalY,
             pair,
             collision,
             bodyA,
             bodyB,
             normal,
-            separation,
-            penetration,
-            positionImpulseA,
-            positionImpulseB,
+            bodyBtoA,
             contactShare,
-            bodyBtoAX,
-            bodyBtoAY,
             positionImpulse,
-            impulseCoefficient = timeScale * Resolver._positionDampen;
-
-        for (i = 0; i < bodies.length; i++) {
-            var body = bodies[i];
-            body.previousPositionImpulse.x = body.positionImpulse.x;
-            body.previousPositionImpulse.y = body.positionImpulse.y;
-        }
+            contactCount = {},
+            tempA = Vector._temp[0],
+            tempB = Vector._temp[1],
+            tempC = Vector._temp[2],
+            tempD = Vector._temp[3];
 
         // find impulses required to resolve penetration
         for (i = 0; i < pairs.length; i++) {
@@ -88,35 +78,39 @@ var Bounds = require('../geometry/Bounds');
             bodyB = collision.parentB;
             normal = collision.normal;
 
-            positionImpulseA = bodyA.previousPositionImpulse;
-            positionImpulseB = bodyB.previousPositionImpulse;
+            // get current separation between body edges involved in collision
+            bodyBtoA = Vector.sub(Vector.add(bodyB.positionImpulse, bodyB.position, tempA), 
+                                    Vector.add(bodyA.positionImpulse, 
+                                        Vector.sub(bodyB.position, collision.penetration, tempB), tempC), tempD);
 
-            penetration = collision.penetration;
+            pair.separation = Vector.dot(normal, bodyBtoA);
+        }
+        
+        for (i = 0; i < pairs.length; i++) {
+            pair = pairs[i];
 
-            bodyBtoAX = positionImpulseB.x - positionImpulseA.x + penetration.x;
-            bodyBtoAY = positionImpulseB.y - positionImpulseA.y + penetration.y;
-
-            normalX = normal.x;
-            normalY = normal.y;
-
-            separation = normalX * bodyBtoAX + normalY * bodyBtoAY;
-            pair.separation = separation;
-
-            positionImpulse = (separation - pair.slop) * impulseCoefficient;
+            if (!pair.isActive || pair.isSensor)
+                continue;
+            
+            collision = pair.collision;
+            bodyA = collision.parentA;
+            bodyB = collision.parentB;
+            normal = collision.normal;
+            positionImpulse = (pair.separation - pair.slop) * timeScale;
 
             if (bodyA.isStatic || bodyB.isStatic)
                 positionImpulse *= 2;
             
             if (!(bodyA.isStatic || bodyA.isSleeping)) {
-                contactShare = positionImpulse / bodyA.totalContacts;
-                bodyA.positionImpulse.x += normalX * contactShare;
-                bodyA.positionImpulse.y += normalY * contactShare;
+                contactShare = Resolver._positionDampen / bodyA.totalContacts;
+                bodyA.positionImpulse.x += normal.x * positionImpulse * contactShare;
+                bodyA.positionImpulse.y += normal.y * positionImpulse * contactShare;
             }
 
             if (!(bodyB.isStatic || bodyB.isSleeping)) {
-                contactShare = positionImpulse / bodyB.totalContacts;
-                bodyB.positionImpulse.x -= normalX * contactShare;
-                bodyB.positionImpulse.y -= normalY * contactShare;
+                contactShare = Resolver._positionDampen / bodyB.totalContacts;
+                bodyB.positionImpulse.x -= normal.x * positionImpulse * contactShare;
+                bodyB.positionImpulse.y -= normal.y * positionImpulse * contactShare;
             }
         }
     };
@@ -347,4 +341,4 @@ var Bounds = require('../geometry/Bounds');
         }
     };
 
-})();
\ No newline at end of file
+})();
diff --git a/src/core/Engine.js b/src/core/Engine.js
index 4afd6f4..644a4d7 100644
--- a/src/core/Engine.js
+++ b/src/core/Engine.js
@@ -195,7 +195,7 @@ var Body = require('../body/Body');
         // iteratively resolve position between collisions
         Resolver.preSolvePosition(pairs.list);
         for (i = 0; i < engine.positionIterations; i++) {
-            Resolver.solvePosition(pairs.list, allBodies, timing.timeScale);
+            Resolver.solvePosition(pairs.list, timing.timeScale);
         }
         Resolver.postSolvePosition(allBodies);