Added updateVelocity argument to Body.setPosition, Body.setAngle, Body.translate, Body.rotate

Added Body.setSpeed, Body.setAngularSpeed
Added Body.getSpeed, Body.getVelocity, Body.getAngularVelocity
Changed all velocity functions to be time independent

src/body/Body.js

@@ -456,15 +456,26 @@ var Axes = require('../geometry/Axes');
     };
 
     /**
-     * Sets the position of the body instantly. Velocity, angle, force etc. are unchanged.
+     * Sets the position of the body instantly. By default velocity, angle, force etc. are unchanged.
+     * If `updateVelocity` is `true` then velocity is inferred from the change in position.
      * @method setPosition
      * @param {body} body
      * @param {vector} position
+     * @param {boolean} [updateVelocity=false]
      */
-    Body.setPosition = function(body, position) {
+    Body.setPosition = function(body, position, updateVelocity) {
         var delta = Vector.sub(position, body.position);
+
+        if (updateVelocity) {
+            body.positionPrev.x = body.position.x;
+            body.positionPrev.y = body.position.y;
+            body.velocity.x = delta.x;
+            body.velocity.y = delta.y;
+            body.speed = Vector.magnitude(delta);
+        } else {
             body.positionPrev.x += delta.x;
             body.positionPrev.y += delta.y;
+        }
 
         for (var i = 0; i < body.parts.length; i++) {
             var part = body.parts[i];
@@ -476,14 +487,23 @@ var Axes = require('../geometry/Axes');
     };
 
     /**
-     * Sets the angle of the body instantly. Angular velocity, position, force etc. are unchanged.
+     * Sets the angle of the body instantly. By default angular velocity, position, force etc. are unchanged.
+     * If `updateVelocity` is `true` then angular velocity is inferred from the change in angle.
      * @method setAngle
      * @param {body} body
      * @param {number} angle
+     * @param {boolean} [updateVelocity=false]
      */
-    Body.setAngle = function(body, angle) {
+    Body.setAngle = function(body, angle, updateVelocity) {
         var delta = angle - body.angle;
+        
+        if (updateVelocity) {
+            body.anglePrev = body.angle;
+            body.angularVelocity = delta;
+            body.angularSpeed = Math.abs(delta);
+        } else {
             body.anglePrev += delta;
+        }
 
         for (var i = 0; i < body.parts.length; i++) {
             var part = body.parts[i];
@@ -504,13 +524,49 @@ var Axes = require('../geometry/Axes');
      * @param {vector} velocity
      */
     Body.setVelocity = function(body, velocity) {
-        body.positionPrev.x = body.position.x - velocity.x;
-        body.positionPrev.y = body.position.y - velocity.y;
-        body.velocity.x = velocity.x;
-        body.velocity.y = velocity.y;
+        var timeScale = body.deltaTime / Common._timeUnit;
+        body.positionPrev.x = body.position.x - velocity.x * timeScale;
+        body.positionPrev.y = body.position.y - velocity.y * timeScale;
+        body.velocity.x = velocity.x * timeScale;
+        body.velocity.y = velocity.y * timeScale;
         body.speed = Vector.magnitude(body.velocity);
     };
 
+    /**
+     * Gets the linear velocity of the body. Use this instead of the internal `body.velocity`.
+     * @method getVelocity
+     * @param {body} body
+     * @return {vector} velocity
+     */
+    Body.getVelocity = function(body) {
+        var timeScale = Common._timeUnit / body.deltaTime;
+
+        return {
+            x: (body.position.x - body.positionPrev.x) * timeScale,
+            y: (body.position.y - body.positionPrev.y) * timeScale
+        };
+    };
+
+    /**
+     * Gets the linear speed the body. Use this instead of the internal `body.speed`.
+     * @method getSpeed
+     * @param {body} body
+     * @return {number} speed
+     */
+    Body.getSpeed = function(body) {
+        return Vector.magnitude(Body.getVelocity(body));
+    };
+
+    /**
+     * Sets the linear speed of the body. Use this instead of the internal `body.speed`.
+     * @method setSpeed
+     * @param {body} body
+     * @param {number} speed
+     */
+    Body.setSpeed = function(body, speed) {
+        Body.setVelocity(body, Vector.mult(Vector.normalise(Body.getVelocity(body)), speed));
+    };
+
     /**
      * Sets the angular velocity of the body instantly. Position, angle, force etc. are unchanged. See also `Body.applyForce`.
      * @method setAngularVelocity
@@ -518,31 +574,66 @@ var Axes = require('../geometry/Axes');
      * @param {number} velocity
      */
     Body.setAngularVelocity = function(body, velocity) {
-        body.anglePrev = body.angle - velocity;
-        body.angularVelocity = velocity;
+        var timeScale = body.deltaTime / Common._timeUnit;
+        body.anglePrev = body.angle - velocity * timeScale;
+        body.angularVelocity = velocity * timeScale;
         body.angularSpeed = Math.abs(body.angularVelocity);
     };
 
     /**
-     * Moves a body by a given vector relative to its current position, without imparting any velocity.
-     * @method translate
+     * Gets the angular velocity of the body. Use this instead of the internal `body.angularVelocity`.
+     * @method getAngularVelocity
      * @param {body} body
-     * @param {vector} translation
+     * @return {number} angular velocity
      */
-    Body.translate = function(body, translation) {
-        Body.setPosition(body, Vector.add(body.position, translation));
+    Body.getAngularVelocity = function(body) {
+        return (body.angle - body.anglePrev) * Common._timeUnit / body.deltaTime;
     };
 
     /**
-     * Rotates a body by a given angle relative to its current angle, without imparting any angular velocity.
+     * Gets the angular speed of the body. Use this instead of the internal `body.angularSpeed`.
+     * @method getAngularSpeed
+     * @param {body} body
+     * @return {number} angular speed
+     */
+    Body.getAngularSpeed = function(body) {
+        return Math.abs(Body.getAngularVelocity(body));
+    };
+
+    /**
+     * Sets the angular speed of the body. Use this instead of the internal `body.angularSpeed`.
+     * @method setAngularSpeed
+     * @param {body} body
+     * @param {number} speed
+     */
+    Body.setAngularSpeed = function(body, speed) {
+        Body.setAngularVelocity(body, Common.sign(Body.getAngularVelocity(body)) * speed);
+    };
+
+    /**
+     * Moves a body by a given vector relative to its current position, without imparting any velocity by default.
+     * If `updateVelocity` is `true` then velocity is inferred from the change in position.
+     * @method translate
+     * @param {body} body
+     * @param {vector} translation
+     * @param {boolean} [updateVelocity=false]
+     */
+    Body.translate = function(body, translation, updateVelocity) {
+        Body.setPosition(body, Vector.add(body.position, translation), updateVelocity);
+    };
+
+    /**
+     * Rotates a body by a given angle relative to its current angle, without imparting any angular velocity by default.
+     * If `updateVelocity` is `true` then angular velocity is inferred from the change in angle.
      * @method rotate
      * @param {body} body
      * @param {number} rotation
      * @param {vector} [point]
+     * @param {boolean} [updateVelocity=false]
      */
-    Body.rotate = function(body, rotation, point) {
+    Body.rotate = function(body, rotation, point, updateVelocity) {
         if (!point) {
-            Body.setAngle(body, body.angle + rotation);
+            Body.setAngle(body, body.angle + rotation, updateVelocity);
         } else {
             var cos = Math.cos(rotation),
                 sin = Math.sin(rotation),
@@ -552,9 +643,9 @@ var Axes = require('../geometry/Axes');
             Body.setPosition(body, {
                 x: point.x + (dx * cos - dy * sin),
                 y: point.y + (dx * sin + dy * cos)
-            });
+            }, updateVelocity);
 
-            Body.setAngle(body, body.angle + rotation);
+            Body.setAngle(body, body.angle + rotation, updateVelocity);
         }
     };
 
@@ -863,7 +954,7 @@ var Axes = require('../geometry/Axes');
      */
 
     /**
-     * A `Number` that _measures_ the current speed of the body after the last `Body.update`. It is read-only and always positive (it's the magnitude of `body.velocity`).
+     * Internal only. Use `Body.getSpeed` and `Body.setSpeed` instead.
      *
      * @readOnly
      * @property speed
@@ -872,7 +963,7 @@ var Axes = require('../geometry/Axes');
      */
 
     /**
-     * A `Number` that _measures_ the current angular speed of the body after the last `Body.update`. It is read-only and always positive (it's the magnitude of `body.angularVelocity`).
+     * Internal only. Use `Body.getAngularSpeed` and `Body.setAngularSpeed` instead.
      *
      * @readOnly
      * @property angularSpeed
@@ -881,8 +972,7 @@ var Axes = require('../geometry/Axes');
      */
 
     /**
-     * A `Vector` that _measures_ the current velocity of the body after the last `Body.update`. It is read-only. 
-     * If you need to modify a body's velocity directly, you should either apply a force or simply change the body's `position` (as the engine uses position-Verlet integration).
+     * Internal only. Use `Body.getVelocity` and `Body.setVelocity` instead.
      * 
      * @readOnly
      * @property velocity
@@ -891,8 +981,7 @@ var Axes = require('../geometry/Axes');
      */
 
     /**
-     * A `Number` that _measures_ the current angular velocity of the body after the last `Body.update`. It is read-only. 
-     * If you need to modify a body's angular velocity directly, you should apply a torque or simply change the body's `angle` (as the engine uses position-Verlet integration).
+     * Internal only. Use `Body.getAngularVelocity` and `Body.setAngularVelocity` instead.
      *
      * @readOnly
      * @property angularVelocity