Simple contact seam in SpriteKit doesn't work as expected
I want to make a pendulum. Starting with SKScene and everything by default, I do the following ...
- (void)createSceneContents {
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.view.bounds];
// object 1 is the fulcrum
SKSpriteNode *object1 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(5, 5)];
[self addChild:object1];
object1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object1.frame.size];
object1.physicsBody.dynamic = NO;
object1.position = self.view.center;
// object2 is like a broomstick, which I will pin to the fulcrum
SKSpriteNode *object2 = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(90, 2)];
[self addChild:object2];
object2.anchorPoint = CGPointMake(0.0, 0.5);
object2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object2.frame.size];
object2.position = self.view.center;
// pin the physics bodies
SKPhysicsJointPin *pinJoint = [SKPhysicsJointPin jointWithBodyA:object1.physicsBody bodyB:object2.physicsBody anchor:object1.position];
[self.physicsWorld addJoint:pinJoint];
}
If I don't add inference logic as expected, the fulcrum stays in the middle of the scene and the broom falls to the floor, so I know the broom is subject to gravity. After adding the pin, I get this:
No movement. What for? It also causes no movement ...
[object2.physicsBody applyForce:CGVectorMake(0, -5)];
I expect the broom to wobble and wobble because it is attached to the support. I saw articles about positioning knots first before joints, but I did. Am I wrong to make the broom swing? How can I get it to do this?
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Node 2 have the wrong anchorPoint defined, download an example here:
Picture
Swift 3 code:
let nodeSize = CGSize(width: 10, height: 10)
let node = SKSpriteNode(color: .red, size: nodeSize)
node.physicsBody = SKPhysicsBody(rectangleOf: nodeSize)
node.physicsBody?.isDynamic = false
self.addChild(node)
let node2Size = CGSize(width: 60, height: 8)
let node2 = SKSpriteNode(color: .green, size: node2Size)
node2.position = CGPoint(x: 30, y: 0)
node2.physicsBody = SKPhysicsBody(rectangleOf: node2Size)
node2.physicsBody?.mass = 1.0
self.addChild(node2)
let a = SKPhysicsJointPin.joint(withBodyA: node.physicsBody! , bodyB: node2.physicsBody!, anchor: CGPoint(x: 0.0, y: 0.0))
self.physicsWorld.add(a)
Objective-C:
SKSpriteNode *object1 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(5, 5)];
[self addChild:object1];
object1.position = self.view.center;
object1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object1.frame.size];
object1.physicsBody.dynamic = NO;
SKSpriteNode *object2 = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(90, 2)];
[self addChild:object2];
object2.position = CGPointMake(self.view.center.x+45, self.view.center.y);
object2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object2.frame.size];
SKPhysicsJointPin *pinJoint = [SKPhysicsJointPin jointWithBodyA:object1.physicsBody bodyB:object2.physicsBody anchor:self.view.center];
[self.physicsWorld addJoint:pinJoint];
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Thanks to @Maetschl, I was able to make it work in Objective-c like this (removing the anchor point and just positioning the swinging node to one edge) ...
SKSpriteNode *object1 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(5, 5)];
[self addChild:object1];
object1.position = self.view.center;
object1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object1.frame.size];
object1.physicsBody.dynamic = NO;
SKSpriteNode *object2 = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(90, 2)];
[self addChild:object2];
object2.position = CGPointMake(self.view.center.x+45, self.view.center.y);
object2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object2.frame.size];
SKPhysicsJointPin *pinJoint = [SKPhysicsJointPin jointWithBodyA:object1.physicsBody bodyB:object2.physicsBody anchor:self.view.center];
[self.physicsWorld addJoint:pinJoint];
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