SpriteKit Jumping and moving issues

Question

I'm fairly new to swift, and have been working on a game for fun, and i'm running into something I can't quite get my head around.

When the run button is pressed, the character moves forward with the following function

func move(dt: CGFloat) {
  position.x += moveRate * dt
}

And when the jump button is pressed, the character jumps with the following function

func jump() {
  physicsBody?.applyImpulse(CGVector(dx: 0, dy: jumpRate))
  run(jumpAnimation!)
}

both work fine, but consider this senario. The player is running, and then they jump while still moving. While in the air, the player releases the move button and the player's x position stops dead. This obviously feels very unnatural, and i would like the player's x position to ease out.

Now i have also played with moving the character with physicsBody?.applyForce(CGVector(dx: 1000, dy: 0)) which would give that effect, but he seems to just gain more and more speed and you don't get a constant rate or "max speed" so to speak.

Could anybody share some insight with me? I'd love to learn anything I can about spritekit and game development in general. Thanks!

From what I've seen, changing position manually at the same time while using forces never worked well. Try to use either just forces or change node's position by affecting on its position property. Also, apply force should be called within update: method, every frame (unlike applyImpulse method). — Whirlwind
Even changing velocity vector directly while using forces and impulses will play nicely, so maybe you can play with that to... — Whirlwind
been playing with the physicsBody a lot more on all of the objects. It's finicky it seems but i am achiving a better result with applyForce and applyImpluse. What do you mean by "changing velocity vector directly"??? — Shan Robertson
When you apply forces or impulses to a physics body, you actually change its velocity vector (physicsBody.velocity) over time. If you do something like physicsBody.velocity.dx = someValue or physicsBody.velocity = CGVector(dx,dy) you change it directly and instantly. So it depends on your game what kind of effect you are trying to achieve - more natural (eg. using applyForce) or something else... — Whirlwind
For example, in old platformer games, there were no physics, so characters were moving with instant and, in many games, at constant speed :) Today, applyForce do all that physics calculation work so character will not start walking immediately with its desired speed, but rather it will gradually speed up so everything will look more natural. If you want that old style type of moving objects, then change velocity directly . — Whirlwind

Crazyrems Crazyrems · Accepted Answer · 2016-12-07T09:49:07

You should try to set the velocity instead of setting the X position. When setting the position you bypass all the physics behaviors.
You should also try to set it only when you actually press a button.

func move(dt: CGFloat) {
    if Math.abs(moveRate) > 0.1 { // If player initiates movement. You can increase the value 0.1 if you want to filter move values
        velocity = CGVector(dx: moveRate, dy: veloxity.dy)
    }
}

It your character moves indefinitely like in space, linearDamping will be useful. it's used to simulate air friction, so values closer to 1 means more friction and values closer to 0 means less friction.

linearDamping = 0.85

Also, this way, moveRate isn't dt dependent but it should be lowered.

Try it, I haven't tested it yet, but that's basically how I would do it.

SpriteKit Jumping and moving issues

2 Answers