我认为您在模拟水时有三种可能的选择。
1)如评论中所述,您可以尝试使用SKFieldNode(iOS 8+)。但是根据个人经验,该字段节点并没有真正满足我的需求,因为除非您对其进行大量自定义,否则您无法对模拟进行很好地控制,如果这样的话,您可能会最好从头开始计算并减少复杂性。
2)当精灵在水中时,您可以调整其线性和旋转阻尼。实际上,甚至苹果在他们的文档中也提到了这一点。但是这不会给您浮力。
linearDamping和angularDamping属性用于计算物体在移动过程中的摩擦力。例如,这可以用来模拟空气或水的摩擦。
3)自己执行计算。在update方法中,检查物体何时进入“水”以及何时可以计算粘度和/或浮力,并相应地调整节点的速度。在我看来,这是最好的选择,但也是更困难的选择。
编辑:我刚刚用Swift写了一个选项3的快速示例。我认为这就是您要寻找的内容。我在顶部添加了因子常数,因此您可以将其调整为完全符合您的要求。运动是动态应用的,因此它不会干扰您当前的速度(即您可以在水中控制您的角色)。下面是场景的代码和gif。请注意,假定delta time为每秒60帧(1/60),并且没有速度夹紧。这些是您可能需要或不需要的功能,具体取决于您的游戏。
class GameScene: SKScene {
let VISCOSITY: CGFloat = 6
let BUOYANCY: CGFloat = 0.4
let OFFSET: CGFloat = 70
var object: SKSpriteNode!
var water: SKSpriteNode!
override func didMoveToView(view: SKView) {
object = SKSpriteNode(color: UIColor.whiteColor(), size: CGSize(width: 25, height: 50))
object.physicsBody = SKPhysicsBody(rectangleOfSize: object.size)
object.position = CGPoint(x: self.size.width/2.0, y: self.size.height-50)
self.addChild(object)
water = SKSpriteNode(color: UIColor.cyanColor(), size: CGSize(width: self.size.width, height: 300))
water.position = CGPoint(x: self.size.width/2.0, y: water.size.height/2.0)
water.alpha = 0.5
self.addChild(water)
self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
}
override func update(currentTime: CFTimeInterval) {
if water.frame.contains(CGPoint(x:object.position.x, y:object.position.y-object.size.height/2.0)) {
let rate: CGFloat = 0.01;
let disp = (((water.position.y+OFFSET)+water.size.height/2.0)-((object.position.y)-object.size.height/2.0)) * BUOYANCY
let targetPos = CGPoint(x: object.position.x, y: object.position.y+disp)
let targetVel = CGPoint(x: (targetPos.x-object.position.x)/(1.0/60.0), y: (targetPos.y-object.position.y)/(1.0/60.0))
let relVel: CGVector = CGVector(dx:targetVel.x-object.physicsBody.velocity.dx*VISCOSITY, dy:targetVel.y-object.physicsBody.velocity.dy*VISCOSITY);
object.physicsBody.velocity=CGVector(dx:object.physicsBody.velocity.dx+relVel.dx*rate, dy:object.physicsBody.velocity.dy+relVel.dy*rate);
}
}
override func touchesEnded(touches: NSSet!, withEvent event: UIEvent!) {object.position = (touches.anyObject() as UITouch).locationInNode(self);object.physicsBody.velocity = CGVectorMake(0, 0)}
}
Objective-C
#import "GameScene.h"
#define VISCOSITY 6.0
#define BUOYANCY 0.4
#define OFFSET 70.0
@interface GameScene ()
@property (nonatomic, strong) SKSpriteNode* object;
@property (nonatomic, strong) SKSpriteNode* water;
@end
@implementation GameScene
-(void)didMoveToView:(SKView *)view {
_object = [[SKSpriteNode alloc] initWithColor:[UIColor whiteColor] size:CGSizeMake(25, 50)];
self.object.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:self.object.size];
self.object.position = CGPointMake(self.size.width/2.0, self.size.height-50);
[self addChild:self.object];
_water = [[SKSpriteNode alloc] initWithColor:[UIColor cyanColor] size:CGSizeMake(self.size.width, 300)];
self.water.position = CGPointMake(self.size.width/2.0, self.water.size.height/2.0);
self.water.alpha = 0.5;
[self addChild:self.water];
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
}
-(void)update:(NSTimeInterval)currentTime {
if (CGRectContainsPoint(self.water.frame, CGPointMake(self.object.position.x,self.object.position.y-self.object.size.height/2.0))) {
const CGFloat rate = 0.01;
const CGFloat disp = (((self.water.position.y+OFFSET)+self.water.size.height/2.0)-((self.object.position.y)-self.object.size.height/2.0)) * BUOYANCY;
const CGPoint targetPos = CGPointMake(self.object.position.x, self.object.position.y+disp);
const CGPoint targetVel = CGPointMake((targetPos.x-self.object.position.x)/(1.0/60.0), (targetPos.y-self.object.position.y)/(1.0/60.0));
const CGVector relVel = CGVectorMake(targetVel.x-self.object.physicsBody.velocity.dx*VISCOSITY, targetVel.y-self.object.physicsBody.velocity.dy*VISCOSITY);
self.object.physicsBody.velocity=CGVectorMake(self.object.physicsBody.velocity.dx+relVel.dx*rate, self.object.physicsBody.velocity.dy+relVel.dy*rate);
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
self.object.position = [(UITouch*)[touches anyObject] locationInNode:self];
self.object.physicsBody.velocity = CGVectorMake(0, 0);
}
@end
SKFieldNode
,但我会去看一下。谢谢! - Aleksander