Fixes sprite physics to work correctly with the node graph

Teleportation for physics bodies works again

examples/game/test_physics.dart

@@ -47,12 +47,17 @@ main() async {
 
 class TestBed extends NodeWithSize {
   Sprite _obstacle;
-  PhysicsWorld _physicsNode;
+  PhysicsWorld _world;
+  PhysicsGroup _group;
+  PhysicsGroup _group2;
 
   TestBed() : super(new Size(1024.0, 1024.0)) {
-    _physicsNode = new PhysicsWorld(new Offset(0.0, 100.0));
-    PhysicsGroup group = new PhysicsGroup();
-    _physicsNode.addChild(group);
+    _world = new PhysicsWorld(new Offset(0.0, 100.0));
+    _group = new PhysicsGroup();
+    _group2 = new PhysicsGroup();
+    _group2.position = new Point(50.0, 50.0);
+    _world.addChild(_group);
+    _world.addChild(_group2);
 
     _obstacle = new Sprite(_spriteSheet["ship.png"]);
     _obstacle.position = new Point(512.0, 800.0);
@@ -64,23 +69,17 @@ class TestBed extends NodeWithSize {
       friction: 0.5,
       tag: "obstacle"
     );
-    group.addChild(_obstacle);
-    _physicsNode.addContactCallback(myCallback, "obstacle", "ship", PhysicsContactType.begin);
+    _group.addChild(_obstacle);
+    _world.addContactCallback(myCallback, "obstacle", "ship", PhysicsContactType.begin);
 
-    // Animate obstacle
+    // Animate group
     ActionSequence seq = new ActionSequence([
-      new ActionTween((a) => _obstacle.position = a, new Point(256.0, 800.0), new Point(768.0, 800.0), 1.0, Curves.easeInOut),
-      new ActionTween((a) => _obstacle.position = a, new Point(768.0, 800.0), new Point(256.0, 800.0), 1.0, Curves.easeInOut)
+      new ActionTween((a) => _group.position = a, new Point(-256.0, 0.0), new Point(256.0, 0.0), 1.0, Curves.easeInOut),
+      new ActionTween((a) => _group.position = a, new Point(256.0, 0.0), new Point(-256.0, 0.0), 1.0, Curves.easeInOut)
     ]);
-    _obstacle.actions.run(new ActionRepeatForever(seq));
+    _group.actions.run(new ActionRepeatForever(seq));
 
-    seq = new ActionSequence([
-      new ActionTween((a) => _obstacle.scale = a, 1.0, 2.0, 2.0, Curves.easeInOut),
-      new ActionTween((a) => _obstacle.scale = a, 2.0, 1.0, 2.0, Curves.easeInOut)
-    ]);
-    _obstacle.actions.run(new ActionRepeatForever(seq));
-
-    addChild(_physicsNode);
+    addChild(_world);
 
     userInteractionEnabled = true;
   }
@@ -93,35 +92,36 @@ class TestBed extends NodeWithSize {
     if (event.type == "pointerdown") {
       Point pos = convertPointToNodeSpace(event.boxPosition);
 
+      print("ADDING SHIPS");
+      PhysicsGroup group = new PhysicsGroup();
+      group.position = pos;
+      group.rotation = 10.0;
+      group.scale = 0.5;
+      _world.addChild(group);
+
       Sprite shipA;
       shipA = new Sprite(_spriteSheet["ship.png"]);
       shipA.opacity = 0.3;
-      shipA.position = new Point(pos.x - 40.0, pos.y);
+      shipA.position = new Point(-40.0, 0.0);
       shipA.size = new Size(64.0, 64.0);
       shipA.physicsBody = new PhysicsBody(new PhysicsShapeCircle(Point.origin, 32.0),
         friction: 0.5,
         restitution: 0.5,
         tag: "ship"
       );
-      _physicsNode.addChild(shipA);
-      shipA.physicsBody.applyLinearImpulse(
-        new Offset(randomSignedDouble() * 5000.0, randomSignedDouble() * 5000.0),
-        shipA.position
-      );
+      group.addChild(shipA);
 
       Sprite shipB;
       shipB = new Sprite(_spriteSheet["ship.png"]);
       shipB.opacity = 0.3;
-      shipB.position = new Point(pos.x + 40.0, pos.y);
+      shipB.position = new Point(40.0, 0.0);
       shipB.size = new Size(64.0, 64.0);
       shipB.physicsBody = new PhysicsBody(new PhysicsShapePolygon([new Point(-25.0, -25.0), new Point(25.0, -25.0), new Point(25.0, 25.0), new Point(-25.0, 25.0)]),
         friction: 0.5,
         restitution: 0.5,
         tag: "ship"
       );
-      _physicsNode.addChild(shipB);
-
-      new PhysicsJointRevolute(shipA.physicsBody, shipB.physicsBody, pos);
+      group.addChild(shipB);
     }
     return true;
   }

packages/flutter_sprites/lib/src/node.dart

@@ -142,32 +142,61 @@ class Node {
   }
 
   void _updatePhysicsRotation(PhysicsBody body, double rotation, Node physicsParent) {
-    if (physicsParent == null) return;
+    PhysicsWorld world = _physicsWorld(physicsParent);
+    if (world == null) return;
+    world._updateRotation(body, _rotationToPhysics(rotation, physicsParent));
+  }
+
+  PhysicsWorld _physicsWorld(Node parent) {
+    if (parent is PhysicsWorld) {
+      return parent;
+    }
+    else if (parent is PhysicsGroup) {
+      return _physicsWorld(parent.parent);
+    }
+    else {
+      print("physics not found");
+      return null;
+    }
+  }
+
+  double _rotationToPhysics(double rotation, Node physicsParent) {
+    if (physicsParent is PhysicsWorld) {
+      return rotation;
+    } else if (physicsParent is PhysicsGroup) {
+      return _rotationToPhysics(rotation + physicsParent.rotation, physicsParent.parent);
+    } else {
+      assert(false);
+      return null;
+    }
+  }
 
+  double _rotationFromPhysics(double rotation, Node physicsParent) {
     if (physicsParent is PhysicsWorld) {
-      PhysicsWorld world = physicsParent;
-      world._updateRotation(body, rotation);
+      return rotation;
     } else if (physicsParent is PhysicsGroup) {
-      _updatePhysicsRotation(body, rotation + physicsParent.rotation, physicsParent.parent);
+      return _rotationToPhysics(rotation - physicsParent.rotation, physicsParent.parent);
     } else {
       assert(false);
+      return null;
     }
   }
 
-  void _setRotationFromPhysics(double rotation) {
+  void _setRotationFromPhysics(double rotation, Node physicsParent) {
     assert(rotation != null);
-    _rotation = rotation;
+    _rotation = _rotationFromPhysics(rotation, physicsParent);
     invalidateTransformMatrix();
   }
 
   void teleportRotation(double rotation) {
     assert(rotation != null);
-    if (_physicsBody != null && parent is PhysicsWorld) {
+    if (_physicsBody != null && (parent is PhysicsWorld || parent is PhysicsGroup)) {
+      rotation = _rotationToPhysics(rotation, parent);
       _physicsBody._body.setTransform(_physicsBody._body.position, radians(rotation));
       _physicsBody._body.angularVelocity = 0.0;
       _physicsBody._body.setType(box2d.BodyType.STATIC);
     }
-    _setRotationFromPhysics(rotation);
+    _setRotationFromPhysics(rotation, parent);
   }
 
   /// The position of this node relative to its parent.
@@ -188,29 +217,51 @@ class Node {
   }
 
   void _updatePhysicsPosition(PhysicsBody body, Point position, Node physicsParent) {
-    if (physicsParent == null) return;
+    PhysicsWorld world = _physicsWorld(physicsParent);
+    if (world == null) return;
+    world._updatePosition(body, _positionToPhysics(position, physicsParent));
+  }
 
+  Point _positionToPhysics(Point position, Node physicsParent) {
     if (physicsParent is PhysicsWorld) {
-      PhysicsWorld world = physicsParent;
-      world._updatePosition(body, position);
+      return position;
     } else if (physicsParent is PhysicsGroup) {
+      // Transform the position
       Vector4 parentPos = physicsParent.transformMatrix.transform(new Vector4(position.x, position.y, 0.0, 1.0));
-      _updatePhysicsPosition(body, new Point(parentPos.x, parentPos.y), physicsParent.parent);
+      Point newPos = new Point(parentPos.x, parentPos.y);
+      return _positionToPhysics(newPos, physicsParent.parent);
     } else {
       assert(false);
+      return null;
     }
   }
 
-  void _setPositionFromPhysics(Point position) {
+  void _setPositionFromPhysics(Point position, Node physicsParent) {
     assert(position != null);
-    _position = position;
+    _position = _positionFromPhysics(position, physicsParent);
     invalidateTransformMatrix();
   }
 
+  Point _positionFromPhysics(Point position, Node physicsParent) {
+    if (physicsParent is PhysicsWorld) {
+      return position;
+    } else if (physicsParent is PhysicsGroup) {
+      // Transform the position
+      Matrix4 inverseTransform = new Matrix4.copy(physicsParent.transformMatrix);
+      inverseTransform.invert();
+      Vector4 parentPos = inverseTransform.transform(new Vector4(position.x, position.y, 0.0, 1.0));
+      Point newPos = new Point(parentPos.x, parentPos.y);
+      return _positionToPhysics(newPos, physicsParent.parent);
+    } else {
+      assert(false);
+      return null;
+    }
+  }
+
   void teleportPosition(Point position) {
     assert(position != null);
-    if (_physicsBody != null && parent is PhysicsWorld) {
-      PhysicsWorld physicsNode = parent;
+    if (_physicsBody != null && (parent is PhysicsWorld || parent is PhysicsGroup)) {
+      position = _positionToPhysics(position, parent);
       _physicsBody._body.setTransform(
         new Vector2(
           position.x / physicsNode.b2WorldToNodeConversionFactor,
@@ -221,7 +272,7 @@ class Node {
       _physicsBody._body.linearVelocity = new Vector2.zero();
       _physicsBody._body.setType(box2d.BodyType.STATIC);
     }
-    _setPositionFromPhysics(position);
+    _setPositionFromPhysics(position, parent);
   }
 
   /// The skew along the x-axis of this node in degrees.
@@ -287,14 +338,17 @@ class Node {
 
   void _updatePhysicsScale(PhysicsBody body, double scale, Node physicsParent) {
     if (physicsParent == null) return;
+    _physicsWorld(physicsParent)._updateScale(body, _scaleToPhysics(scale, physicsParent));
+  }
 
+  double _scaleToPhysics(double scale, Node physicsParent) {
     if (physicsParent is PhysicsWorld) {
-      PhysicsWorld world = physicsParent;
-      world._updateScale(body, scale);
+      return scale;
     } else if (physicsParent is PhysicsGroup) {
-      _updatePhysicsScale(body, scale * physicsParent.scale, physicsParent.parent);
+      return _scaleToPhysics(scale * physicsParent.scale, physicsParent.parent);
     } else {
       assert(false);
+      return null;
     }
   }
 

packages/flutter_sprites/lib/src/physics_body.dart

@@ -296,8 +296,13 @@ class PhysicsBody {
   void _attach(PhysicsWorld physicsNode, Node node) {
     assert(_attached == false);
 
+    // Account for physics groups
+    Point positionWorld = node._positionToPhysics(node.position, node.parent);
+    double rotationWorld = node._rotationToPhysics(node.rotation, node.parent);
+    double scaleWorld = node._scaleToPhysics(node.scale, node.parent);
+
     // Update scale
-    _scale = node.scale;
+    _scale = scaleWorld;
 
     // Create BodyDef
     box2d.BodyDef bodyDef = new box2d.BodyDef();
@@ -316,9 +321,10 @@ class PhysicsBody {
     else
       bodyDef.type = box2d.BodyType.STATIC;
 
+    // Convert to world coordinates and set position and angle
     double conv = physicsNode.b2WorldToNodeConversionFactor;
-    bodyDef.position = new Vector2(node.position.x / conv, node.position.y / conv);
-    bodyDef.angle = radians(node.rotation);
+    bodyDef.position = new Vector2(positionWorld.x / conv, positionWorld.y / conv);
+    bodyDef.angle = radians(rotationWorld);
 
     // Create Body
     _body = physicsNode.b2World.createBody(bodyDef);

packages/flutter_sprites/lib/src/physics_world.dart

@@ -97,7 +97,7 @@ class PhysicsWorld extends Node {
       }
 
       // Update linear velocity
-      if (body._lastPosition == null) {
+      if (body._lastPosition == null || body._targetPosition == null) {
         b2Body.linearVelocity.setZero();
       } else {
         Vector2 velocity = (body._targetPosition - body._lastPosition) / dt;
@@ -106,7 +106,7 @@ class PhysicsWorld extends Node {
       }
 
       // Update angular velocity
-      if (body._lastRotation == null) {
+      if (body._lastRotation == null || body._targetAngle == null) {
         b2Body.angularVelocity = 0.0;
       } else {
         double angularVelocity = (body._targetAngle - body._lastRotation) / dt;
@@ -129,12 +129,20 @@ class PhysicsWorld extends Node {
       }
 
       // Update visual position and rotation
-      body._node._setPositionFromPhysics(new Point(
-        b2Body.position.x * b2WorldToNodeConversionFactor,
-        b2Body.position.y * b2WorldToNodeConversionFactor
-      ));
+      if (body.type == PhysicsBodyType.dynamic) {
+        body._node._setPositionFromPhysics(
+          new Point(
+            b2Body.position.x * b2WorldToNodeConversionFactor,
+            b2Body.position.y * b2WorldToNodeConversionFactor
+          ),
+          body._node.parent
+        );
 
-      body._node._setRotationFromPhysics(degrees(b2Body.getAngle()));
+        body._node._setRotationFromPhysics(
+          degrees(b2Body.getAngle()),
+          body._node.parent
+        );
+      }
     }
 
     // Break joints