Stefan stolniceanu spritekit, 2 d or not 2d

Introduction to
SpriteKit
Ștefan Stolniceanu

Background
• More and more game developers emerge, all with common
needs
• Need of fast graphics
• Particles and visual effects
• Physics and animation
• Most of the iconic games are 2D
• Rechanges the focus on developing games instead of
engines

SpriteKit Essentials
• Images of Sprites, Shapes and Particles
• Animations and Physics
• Audio, Video, Visual Effects
• And many other
What SpriteKit has to offer

The Parts of a Sprite Kit Game
Scenes
Actions Physics

Displaying Sprite Kit Content
Application UIView / NSView
SKView skView.presentScene(myScene)

Sprite Kit Nodes
The building blocks of every 2D game

The father, the son, and the holy spirit
SKNode
SKLabelNode
SKEmitterNode
SKShapeNode SKSpriteNode
SKEffectNode
SKScene
SKCropNode

SKNode
var position: CGPoint!
var zRotation: CGFloat!
var xScale: CGFloat!
var yScale: CGFloat!
var alpha: CGFloat!
var hidden: Bool!

SKSpriteNode
• Has an explicit size
• Can display a colour
• Can display a texture
• You can blend the texture with a colour
Your true and only friend

SKSpriteNode
SKSpriteNode
• Has an explicit size
• Can display a colour
• Can display a texture
• You can blend the texture with a colour

SKTexture
• Represents Sprite Kit bitmap data
• Automatically managed by the framework

SKSpriteNode
/* how to create a sprite from a png file */
var sprite = SKSpriteNode()
let texture = SKTexture(imageNamed:”logo”)
sprite.texture = texture
sprite.size = texture.size
VS.
var sprite = SKSpriteNode(imageNamed: “logo”)

SKEmitterNode
That special something something

SKEmitterNode
• Full featured 2D particle system
• Standard startValue and speed
• Advanced keyframe sequence controls

SKEmitterNode
• Texture
• Scale
• Rotation
• Emission angle
• Emission speed
• Blend modes

SKEmitterNode
• Data driven particle effects
• Built-in Xcode editor
• Reduce iteration time
• Empower artists

SKVideoNode
–Me
“VideoNode, VideoNode,
VideoNode does whatever a VideoNode does
Can it be less simple?
No, it can’t.
It is a Node, yes it is.
Lookout!
It is the VideoNode!”

SKVideoNode
Video as a first class sprite
• Until now video has been:
• Above your game view
• Below your game view
• Roll your own in OpenGL
• Anywhere else but where you wanted it to be
• Then comes Sprite Kit, making it a first class sprite

SKVideoNode
Video as a first class sprite
• One-line creation
let video = SKVideoNode(videoFileNamed: “video”)
• Built on AVPlayer

SKShapeNode
• Dynamic shapes
• Any CGPath
• Built for speed
• Rendered in hardware
• Stroke and/or fill
• Add glow effects
• Multiple subpaths

SKLabelNode
• For most text use UIKit/AppKit
• Single line text as a sprite
• Supports all system fonts
• Supports SKActions (of course)

SKEffectNode
• Flattens children during render
• shouldEnableEffects
• Group opacity
• Group blend modes
• Optionally apply a CIFilter
• Can cache via shouldRasterize

SKCropNode
• Mask content of children
• Mask defined as a SKNode
• Transparent area is masked out
• Mask node can have children
• Mask node can run SKActions

SKAction
Super simple to use,
It can be compared to a scripting language for SK

Basic SKActions
var action: SKAction!
action = SKAction.rotateByAngle(M_PI, duration: 1.0)
action = SKAction.moveTo(aCGPoint, duration: 1.0)
action = SKAction.fadeAlphaTo(0.75, duration: 1.0)
action = SKAction.scaleBy(2.0, duration: 1.0)
action = SKAction.scaleXBy(1.5, y: 0.5, duration: 1.0)

Running SKActions
It’s alive!
• Actions run immediately
• Copy on add
• Removed on completion
sprite.runAction(SKAction.fadeOutWithDuration:1.0))

Running SKActions
• Repeating an action
var dance = SKAction.runBlock(dance)
var danceUntilYouDrop = SKAction.repeatAction(dance, count: 20)
• Repeating an action… forever!
var dance = SKAction.runBlock(dance)
var danceLikeYourLifeDependsOnIt = SKAction.repeatActionForever(dance)

Sequences
Reuse already defined blocks
funkyGuy.runAction(SKAction.sequence([danceSalsa, robotDance, doTheFlop]))
danceSalsa robotDance doTheFlop
SKAction Sequence

Groups
crazyGuy.runAction(SKAction.group([danceSalsa, robotDance, doTheFlop]))
danceSalsa
robotDance
doTheFlop
SKAction Group

Sequences… of groups!
crazyDrunkGuy.runAction(SKAction.sequence([drinkALot, dance, regret]))
danceSalsa
robotDance
doTheFlop
SKAction Sequences of Groups
let dance = SKAction.group([danceSalsa, robotDance, doTheFlop])
regretdrinkALot

Physics in Sprite Kit
Truly integrated physics
• Built right into Sprite Kit
• You don’t care about the synchronisation process
• Not a global on/off switch
• Enabled node-by-node
• No performance penalty for what you’re not using

SKPhysicsBody
• Any nodes can have a PhysicsBody
• To do so… whelp… just add one
• You have some of ‘em predefined already
var aPhysicsBody = SKPhysicsBody(rectangleOfSize: 50)
aSprite.physicsBody = aPhysicsBody

SKPhysicsWorld
• Each SKScene has a physicsWorld
• Perform hit tests, ray casts
• Add joints
• Change gravity
//Down!
self.physicsWorld.gravity = CGVector(0.0, -9.8)
//Up!
self.physicsWorld.gravity = CGVector(0.0, 9.8)

PhysicsWorld Contact Delegate
self.physicsWorld.contactDelegate = self
func didBeginContact(contact: SKPhysicsContact) {}
func didEndContact(contact: SKPhysicsContact) {}

SKPhysicsContact
/* the physics bodies involved */
var bodyA: SKPhysicsBody!
var bodyB: SKPhysicsBody!
/* point of first contact */
var contactPoint: CGPoint!
/* magnitude of collision impulse at that point */
var collisionImpulse: CGFloat!

Collision Groups
var categoryBitMask: UInt32!
var collisionBitMask: UInt32!
var contactTestBitMask: UInt32!

Sprite Kit Game Loop
Frames have it rough

Stefan stolniceanu spritekit, 2 d or not 2d

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Editor's Notes