在精灵工具包中，当我在节点上运行一个动作以将其上移到某个y值时，它会逐渐变慢。 为什么？

Question

I didn't setup any physics and I don't use the scene file. I just setup scene from code.

that's where i setup and fire up the action:

  let GoUpAction = SKAction.moveTo(CGPoint(x:80,y:size.height-hVar),duration:1);
    if node1.position.y < (size.height/6) + 20 {
        node2.runAction(GoUpAction)
    }

and when it executes, node2 start moving up with normal speed but the higher (y++) it gets the slower it moves.

Funny thing - in general that behaviour suites me, but i'd appreciate the slowdown to start only 1/4 away from the destination. Or no slowdown at all.

I didn't set any gravity or anything. very basic setup.

this is how nodes are defined:

    let node2 = SKSpriteNode(imageNamed: "n2")
    node2.name = "n2"
    node2.position = CGPoint(x: size.width-80, y: size.height-hVar)
    node2.xScale = 0.25
    node2.yScale = 0.25
    node2.zPosition = -1
    addChild(node2)

Answer 1

I didn't set any gravity or anything. very basic setup.

The default value is (0.0,-9.8) which may slow down your node in y direction. Try to either set property affectedByGravity of your physic body,

node2.physicsBody.affectedByGravity = NO;

or set "global" gravity when creating your scene,

self.physicsWorld.gravity = CGVectorMake(0.0f, 0.0f);

to get rid of the gravity.

Answer 2

Thank you all for your help!

However the issue was a bit structural. I made a stupid mistake which I didn't think through well by having a certain function being called from the Update method (runs every frame).

This function was actually retriggering the a sprite move action on each frame, but with each frame the distance became less, while time for the action to run was the same, so it produced the slowdown effect:)

I had to rewrite some code in regards what is called when and got rid of this stupid mistake.

All now works as expected:)

But a funny trick to simulate the slowdown though:)