adds simple stress tracking to bodies

src/body/Body.js

@@ -43,6 +43,7 @@ var Body = {};
             angularSpeed: 0,
             velocity: { x: 0, y: 0 },
             angularVelocity: 0,
+            stress: { x: 0, y: 0 },
             isStatic: false,
             isSleeping: false,
             motion: 0,
@@ -429,6 +430,10 @@ var Body = {};
         body.position.x += body.velocity.x;
         body.position.y += body.velocity.y;
 
+        // set stress due to forces
+        body.stress.x = Math.abs(body.force.x * (deltaTime * timeScale * body.timeScale));
+        body.stress.y = Math.abs(body.force.y * (deltaTime * timeScale * body.timeScale));
+
         // update angular velocity with verlet integration
         body.angularVelocity = ((body.angle - body.anglePrev) * frictionAir * correction) + (body.torque / body.inertia) * deltaTimeSquared;
         body.anglePrev = body.angle;

src/collision/Resolver.js

@@ -156,6 +156,9 @@ var Resolver = {};
                     bodyA.positionPrev.x += impulse.x * bodyA.inverseMass;
                     bodyA.positionPrev.y += impulse.y * bodyA.inverseMass;
                     bodyA.anglePrev += Vector.cross(offset, impulse) * bodyA.inverseInertia;
+
+                    bodyA.stress.x += Math.abs(impulse.x);
+                    bodyA.stress.y += Math.abs(impulse.y);
                 }
 
                 if (!(bodyB.isStatic || bodyB.isSleeping)) {
@@ -163,6 +166,9 @@ var Resolver = {};
                     bodyB.positionPrev.x -= impulse.x * bodyB.inverseMass;
                     bodyB.positionPrev.y -= impulse.y * bodyB.inverseMass;
                     bodyB.anglePrev -= Vector.cross(offset, impulse) * bodyB.inverseInertia;
+
+                    bodyB.stress.x += Math.abs(impulse.x);
+                    bodyB.stress.y += Math.abs(impulse.y);
                 }
             }
         }
@@ -269,4 +275,4 @@ var Resolver = {};
         }
     };
 
-})();
+})();

src/constraint/Constraint.js

@@ -213,6 +213,9 @@ var Constraint = {};
             bodyA.position.x -= force.x;
             bodyA.position.y -= force.y;
             bodyA.angle += torque;
+
+            bodyA.stress.x += Math.abs(force.x);
+            bodyA.stress.y += Math.abs(force.y);
         }
 
         if (bodyB && !bodyB.isStatic) {
@@ -233,6 +236,9 @@ var Constraint = {};
             bodyB.position.x += force.x;
             bodyB.position.y += force.y;
             bodyB.angle -= torque;
+
+            bodyB.stress.x += Math.abs(force.x);
+            bodyB.stress.y += Math.abs(force.y);
         }
 
     };
@@ -376,4 +382,4 @@ var Constraint = {};
      * @type number
      */
 
-})();
+})();

src/render/Render.js

@@ -46,7 +46,8 @@ var Render = {};
                 showPositions: false,
                 showAngleIndicator: false,
                 showIds: false,
-                showShadows: false
+                showShadows: false,
+                showStress: false
             }
         };
 
@@ -193,6 +194,9 @@ var Render = {};
         if (options.showVelocity)
             Render.bodyVelocity(engine, bodies, context);
 
+        if (options.showStress)
+            Render.bodyStress(engine, bodies, context);
+
         if (options.showIds)
             Render.bodyIds(engine, bodies, context);
 
@@ -649,6 +653,27 @@ var Render = {};
         }
     };
 
+    Render.bodyStress = function(engine, bodies, context) {
+        var c = context;
+
+        for (var i = 0; i < bodies.length; i++) {
+            var body = bodies[i];
+
+            if (!body.render.visible)
+                continue;
+
+            c.beginPath();
+            c.moveTo(body.position.x + body.stress.x*4, body.position.y);
+            c.lineTo(body.position.x, body.position.y);
+            c.lineTo(body.position.x, body.position.y - body.stress.y*4);
+
+            c.lineWidth = 1;
+            c.strokeStyle = 'teal';
+            c.stroke();
+            
+        }
+    };
+
     /**
      * Description
      * @private