78 lines
2 KiB
Swift
78 lines
2 KiB
Swift
//
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// Metaballs.swift
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// Metaballs
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//
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// Created by Eryn Wells on 7/30/17.
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// Copyright © 2017 Eryn Wells. All rights reserved.
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//
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import Foundation
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public struct Ball {
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let radius: CGFloat
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var position = CGPoint()
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var velocity = CGVector()
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internal var bounds: CGRect {
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let diameter = radius * 2
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return CGRect(x: position.x - radius, y: position.y - radius, width: diameter, height: diameter)
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}
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init(radius r: CGFloat) {
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radius = r
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}
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internal mutating func update() {
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position.x += velocity.dx
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position.y += velocity.dy
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}
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}
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public struct Field {
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var size: CGSize
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private(set) var balls = [Ball]()
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internal var bounds: CGRect {
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return CGRect(origin: CGPoint(), size: size)
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}
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init(size s: CGSize) {
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size = s
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}
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public func update() {
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let selfBounds = bounds
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for var ball in balls {
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// Update position of ball.
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ball.update()
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if !selfBounds.contains(ball.position) {
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// Degenerate case. If the ball finds itself outside the bounds of the field, plop it back in the center.
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ball.position = CGPoint(x: selfBounds.midX, y: selfBounds.midY)
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} else {
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// Do collision detection with walls.
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let ballBounds = ball.bounds
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if !selfBounds.contains(ballBounds) {
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if ballBounds.minX < selfBounds.minX || ballBounds.maxX > selfBounds.maxX {
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ball.velocity.dx *= -1
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}
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if ballBounds.minY < selfBounds.minY || ballBounds.maxY > selfBounds.maxY {
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ball.velocity.dy *= -1
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}
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}
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}
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}
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}
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public func sample(at point: CGPoint) throws -> CGFloat {
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return 0.0
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}
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public mutating func add(ball: Ball) throws {
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guard bounds.contains(ball.bounds) else {
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/// TODO: Throw an error.
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return
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}
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balls.append(ball)
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}
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}
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