CODEWITHSUNDEEP
iosphysicssprite-kit
Cocorico
Cocorico

Reputation: 2347

Best way to add a SKPhysicsJoint to an object

So I have a marionette I am making in Sprite Kit, and placing him in a scene. I have created a Marionette class, which is a subclass of SKNode, and when I create an instance of this class, I add a number of SKSpriteNodes to each other. This should give you an idea of how it works (I've snipped out the unnecessary lines):

[self addChild:self.head];
[self.head addChild:self.chest];
[self.chest addChild:self.leftLeg];
[self.chest addChild:self.rightLeg];
[self.leftLeg addChild:self.leftFoot];
[self.rightLeg addChild:self.rightFoot];

So, after doing this, I have my marionette showing up. I want to add a SKPhysicsJointPin to each of these connections. Code looks like this:

self.chestPin = [SKPhysicsJointPin jointWithBodyA:self.marionette.head.physicsBody bodyB:self.marionette.chest.physicsBody anchor:self.marionette.chest.anchorPoint];

At first I thought I could just set up all the pins inside the Marionette class, but that doesn't work (I get EXC_BAD_ACCESS if I recall). It turns out that I have to add the Marionette to the overall SKScene before I add the joints.

This make sense I guess, but I can't help thinking there should be some way I could just set everything up in the Marionette class, and then stick 2 lines of code in the scene to create a new Marionette, then addChild him to the Scene.

As it is, my SKScene subclass has a bunch of code now to add all the pins, and it doesn't feel like it fits in the Scene. Thoughts?

Upvotes: 2

Views: 772

Answers (1)

CodeSmile
CodeSmile

Reputation: 64477

You don't want to use anchorPoint as anchor. The anchorPoint property is a factor which ranges from 0 to 1 and affects how the texture is offset from the sprite's position, ie the default 0.5/0.5 centers the sprite's texture on the sprite's position. In other words anchorPoint is not a position, and using that will anchor the body & head joint to the lower left corner of the screen.

Instead try using either chest or head's position as anchor, or the point in between the two.

Upvotes: 3

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