implemented compound bodies, added Body.setParts

Author: liabru

src/body/Body.js

@@ -117,6 +117,7 @@ var Body = {};
             vertices: body.vertices,
             isStatic: body.isStatic,
             isSleeping: body.isSleeping,
+            parent: body.parent || body,
             parts: body.parts || [body]
         });
 
@@ -194,6 +195,9 @@ var Body = {};
             case 'angularVelocity':
                 Body.setAngularVelocity(body, value);
                 break;
+            case 'parts':
+                Body.setParts(body, value);
+                break;
             default:
                 body[property] = value;
 
@@ -298,6 +302,78 @@ var Body = {};
         Bounds.update(body.bounds, body.vertices, body.velocity);
     };
 
+    /**
+     * Sets the parts of the `body` and updates mass, inertia and centroid.
+     * Each part will have its parent set to `body`.
+     * By default the convex hull will be automatically computed and set on `body`, unless `autoHull` is set to `false.`
+     * Note that this method will ensure that the first part in `body.parts` will always be the `body`.
+     * @method setParts
+     * @param {body} body
+     * @param [body] parts
+     * @param {bool} [autoHull=true]
+     */
+    Body.setParts = function(body, parts, autoHull) {
+        autoHull = typeof autoHull !== 'undefined' ? autoHull : true;
+
+        // ensure the body is always at index 0
+        var index = Common.indexOf(parts, body);
+        if (index > -1) {
+            parts.splice(index, 1);
+        }
+
+        parts.unshift(body);
+        body.parts = parts;
+
+        if (parts.length === 1)
+            return;
+
+        var i;
+
+        // find the convex hull of all parts to set on the parent body
+        if (autoHull) {
+            var vertices = [];
+            for (i = 1; i < parts.length; i++) {
+                vertices = vertices.concat(parts[i].vertices);
+            }
+
+            Vertices.clockwiseSort(vertices);
+
+            var hull = Vertices.hull(vertices),
+                hullCentre = Vertices.centre(hull);
+
+            Body.setVertices(body, hull);
+            Body.setPosition(body, hullCentre);
+        }
+
+        // find the combined properties of all parts to set on the parent body
+        var mass = 0,
+            area = 0,
+            inertia = 0,
+            centroid = { x: 0, y: 0 };
+
+        for (i = 1; i < parts.length; i++) {
+            var part = parts[i];
+            part.parent = body;
+            mass += part.mass;
+            area += part.area;
+            inertia += part.inertia;
+            Vector.add(centroid, part.position, centroid);
+        }
+
+        centroid = Vector.div(centroid, parts.length - 1);
+
+        body.area = area;
+        body.parent = body;
+        body.position.x = centroid.x;
+        body.position.y = centroid.y;
+        body.positionPrev.x = centroid.x;
+        body.positionPrev.y = centroid.y;
+
+        Body.setMass(body, mass);
+        Body.setInertia(body, inertia);
+        Body.setPosition(body, centroid);
+    };
+
     /**
      * Sets the position of the body instantly. Velocity, angle, force etc. are unchanged.
      * @method setPosition
@@ -314,8 +390,6 @@ var Body = {};
 
         Vertices.translate(body.vertices, delta);
         Bounds.update(body.bounds, body.vertices, body.velocity);
-
-        //Common.each(body.children, Body.setPosition, position);
     };
 
     /**
@@ -333,8 +407,6 @@ var Body = {};
         Vertices.rotate(body.vertices, delta, body.position);
         Axes.rotate(body.axes, delta);
         Bounds.update(body.bounds, body.vertices, body.velocity);
-
-        //Common.each(body.children, Body.setAngle, angle);
     };
 
     /**
@@ -452,6 +524,10 @@ var Body = {};
                 Axes.rotate(part.axes, body.angularVelocity);
             }
             Bounds.update(part.bounds, body.vertices, body.velocity);
+            if (i > 0) {
+                part.position.x += body.velocity.x;
+                part.position.y += body.velocity.y;
+            }
         }
     };
 

src/collision/Detector.js

@@ -41,16 +41,15 @@ var Detector = {};
 
             // mid phase
             if (Bounds.overlaps(bodyA.bounds, bodyB.bounds)) {
-               /*for (var j = 1; j < bodyA.parts.length; j++) {
+                for (var j = bodyA.parts.length > 1 ? 1 : 0; j < bodyA.parts.length; j++) {
                     var partA = bodyA.parts[j];
 
-                    for (var k = 1; k < bodyB.parts.length; k++) {
+                    for (var k = bodyB.parts.length > 1 ? 1 : 0; k < bodyB.parts.length; k++) {
                         var partB = bodyB.parts[k];
 
-                        if (Bounds.overlaps(partA.bounds, partB.bounds)) {*/
-
+                        if ((partA === bodyA && partB === bodyB) || Bounds.overlaps(partA.bounds, partB.bounds)) {
                             // find a previous collision we could reuse
-                            var pairId = Pair.id(bodyA, bodyB),
+                            var pairId = Pair.id(partA, partB),
                                 pair = pairsTable[pairId],
                                 previousCollision;
 
@@ -61,7 +60,7 @@ var Detector = {};
                             }
 
                             // narrow phase
-                            var collision = SAT.collides(bodyA, bodyB, previousCollision);
+                            var collision = SAT.collides(partA, partB, previousCollision);
 
                             // @if DEBUG
                             metrics.narrowphaseTests += 1;
@@ -75,9 +74,9 @@ var Detector = {};
                                 metrics.narrowDetections += 1;
                                 // @endif
                             }
-                       //}
-                    //}
-                //}
+                        }
+                    }
+                }
             }
         }
 

src/collision/Resolver.js

@@ -40,8 +40,8 @@ var Resolver = {};
                 continue;
 
             collision = pair.collision;
-            bodyA = collision.bodyA;
-            bodyB = collision.bodyB;
+            bodyA = collision.parentA;
+            bodyB = collision.parentB;
             vertex = collision.supports[0];
             vertexCorrected = collision.supportCorrected;
             normal = collision.normal;
@@ -61,8 +61,8 @@ var Resolver = {};
                 continue;
 
             collision = pair.collision;
-            bodyA = collision.bodyA;
-            bodyB = collision.bodyB;
+            bodyA = collision.parentA;
+            bodyB = collision.parentB;
             normal = collision.normal;
             positionImpulse = ((pair.separation * _positionDampen) - pair.slop) * timeScale;
 
@@ -102,6 +102,10 @@ var Resolver = {};
                     var part = body.parts[j];
                     Vertices.translate(part.vertices, body.positionImpulse);
                     Bounds.update(part.bounds, body.vertices, body.velocity);
+                    if (j > 0) {
+                        part.position.x += body.positionImpulse.x;
+                        part.position.y += body.positionImpulse.y;
+                    }
                 }
 
                 // dampen accumulator to warm the next step
@@ -142,8 +146,8 @@ var Resolver = {};
 
             contacts = pair.activeContacts;
             collision = pair.collision;
-            bodyA = collision.bodyA;
-            bodyB = collision.bodyB;
+            bodyA = collision.parentA;
+            bodyB = collision.parentB;
             normal = collision.normal;
             tangent = collision.tangent;
 
@@ -197,8 +201,8 @@ var Resolver = {};
                 continue;
 
             var collision = pair.collision,
-                bodyA = collision.bodyA,
-                bodyB = collision.bodyB,
+                bodyA = collision.parentA,
+                bodyB = collision.parentB,
                 normal = collision.normal,
                 tangent = collision.tangent,
                 contacts = pair.activeContacts,

src/collision/SAT.js

@@ -87,6 +87,8 @@ var SAT = {};
         collision.collided = true;
         collision.normal = minOverlap.axis;
         collision.depth = minOverlap.overlap;
+        collision.parentA = collision.bodyA.parent;
+        collision.parentB = collision.bodyB.parent;
 
         bodyA = collision.bodyA;
         bodyB = collision.bodyB;

src/constraint/Constraint.js

@@ -260,6 +260,11 @@ var Constraint = {};
                 }
 
                 Bounds.update(part.bounds, body.vertices);
+
+                if (j > 0) {
+                    part.position.x += impulse.x;
+                    part.position.y += impulse.y;
+                }
             }
 
             impulse.x = 0;

src/geometry/Vertices.js

@@ -337,7 +337,7 @@ var Vertices = {};
         });
 
         return vertices;
-    }
+    };
 
     /**
      * Returns the convex hull of the input vertices as a new array of points.