You are looking for a fluid simulator
This is indeed possible with modern hardware.
Let’s have a look at what we are going to build here.
Components
In order to achieve that we’ll need to
- create several molecules having a physics body and a blurred image
- use a Shader to apply a common color to every pixel having alpha > 0
Molecule
Here’s the Molecule class
import SpriteKit
class Molecule: SKSpriteNode {
init() {
let texture = SKTexture(imageNamed: "molecule")
super.init(texture: texture, color: .clear, size: texture.size())
let physicsBody = SKPhysicsBody(circleOfRadius: 8)
physicsBody.restitution = 0.2
physicsBody.affectedByGravity = true
physicsBody.friction = 0
physicsBody.linearDamping = 0.01
physicsBody.angularDamping = 0.01
physicsBody.density = 0.13
self.physicsBody = physicsBody
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
Shader
Next we need a Fragment Shader, let’s create a file with name Water.fsh
void main() {
vec4 current_color = texture2D(u_texture, v_tex_coord);
if (current_color.a > 0) {
current_color.r = 0.0;
current_color.g = 0.57;
current_color.b = 0.95;
current_color.a = 1.0;
} else {
current_color.a = 0.0;
}
gl_FragColor = current_color;
}
Scene
And finally we can define the scene
import SpriteKit
class GameScene: SKScene {
lazy var label: SKLabelNode = {
return childNode(withName: "label") as! SKLabelNode
}()
let effectNode = SKEffectNode()
override func didMove(to view: SKView) {
physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
effectNode.shouldEnableEffects = true
effectNode.shader = SKShader(fileNamed: "Water")
addChild(effectNode)
}
var touchLocation: CGPoint?
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
guard let touch = touches.first else { return }
let touchLocation = touch.location(in: self)
if label.contains(touchLocation) {
addRedCircle(location: touchLocation)
} else {
self.touchLocation = touchLocation
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
touchLocation = nil
}
override func update(_ currentTime: TimeInterval) {
if let touchLocation = touchLocation {
let randomizeX = CGFloat(arc4random_uniform(20)) - 10
let randomizedLocation = CGPoint(x: touchLocation.x + randomizeX, y: touchLocation.y)
addMolecule(location: randomizedLocation)
}
}
private func addMolecule(location: CGPoint) {
let molecule = Molecule()
molecule.position = location
effectNode.addChild(molecule)
}
private func addRedCircle(location: CGPoint) {
let texture = SKTexture(imageNamed: "circle")
let sprite = SKSpriteNode(texture: texture)
let physicsBody = SKPhysicsBody(circleOfRadius: texture.size().width / 2)
physicsBody.restitution = 0.2
physicsBody.affectedByGravity = true
physicsBody.friction = 0.1
physicsBody.linearDamping = 0.1
physicsBody.angularDamping = 0.1
physicsBody.density = 1
sprite.physicsBody = physicsBody
sprite.position = location
addChild(sprite)
}
}
The full project is available on my GitHub account https://github.com/lucaangeletti/SpriteKitAqua