Sprite Kit: Prevent SKSpriteNode From Gliding Around

Question

I'm working on a spaceship game for OS X using SpriteKit. This is how I setup physicsBody for my spaceship node.

// SKSpriteNode
ship.physicsBody = [SKPhysicsBody bodyWithPolygonFromPath:triangle];

ship.physicsBody.categoryBitMask = playerCategory;
ship.physicsBody.contactTestBitMask = enemyCategory | edgeCategory;
ship.physicsBody.collisionBitMask = enemyCategory | edgeCategory;

ship.physicsBody.allowsRotation = NO;
ship.physicsBody.dynamic = YES;
ship.physicsBody.linearDamping = 0;
ship.physicsBody.angularDamping = 0.1;
ship.physicsBody.mass = 0.1;
ship.physicsBody.restitution = 0;

This is how I setup physicsWorld and physicsBody in my scene file.

// SKScene
self.physicsWorld.contactDelegate = self;
self.physicsWorld.gravity = CGVectorMake(0, 0);

self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.physicsBody.categoryBitMask = edgeCategory;
self.physicsBody.contactTestBitMask = missileCategory | enemyCategory | playerCategory;
self.physicsBody.collisionBitMask = playerCategory;

self.physicsBody.restitution = 0;

In my scene's update method, I call [ship accelerate:@"up"];, which ends up calling this.

[self.physicsBody applyForce:CGVectorMake(self.engineThrust * cosf(self.shipOrientation),
                                          self.engineThrust * sinf(self.shipOrientation))];

Is there a way to disable the ship's inertia? I don't want my ship gliding along my scene. I want the ship to stop moving as soon as I release the key. I also want the ship to immediately change direction when toggling between the up arrow and the down arrow.

Is there something in physicsBody that I can change or will I have to implement this?

Answer 1

You can stop any inertia by using ship.physicsBody.velocity = CGVectorMake(0,0);