NullHypothesis - 7 months ago 46

Swift Question

I'm still a beginner to UIKit but i'm working on something and I created a dynamic framework to spawn monsters and have them go along pre-determined waypoints from a config file.

So for a given monster, I started setting simple waypoints like go across the screen, or go along a particular path based on (x,y) coordinates. Each path has a series of waypoints, and the monster follows it, then reverses.

This works great, but now I want to have the monsters jump up along an arc (so something quadratic/parabolic). So I thought to myself this is fairly easy, simply create the waypoints to represent an arc, and i'll achieve this.

Right now i'm simply doing

`SKAction.MoveBy(x,y, duration)`

Well it worked, but the animation isn't smooth because I just guessed at the waypoints, instead of using an actual mathematical parabolic function. So I did things like:

`(5, 10),`

(5, 10),

(10, 10),

(15, 10),

.. and then on the way down

(-15, -10)

..

etc

So I think I either need to do 2 things, which i'm unsure about:

- Find something (website / tool / math function?) that can generate the smoother, proper set of (x,y) coordinates for arcs quickly for me so I can then input them into my config file and achieve a smooth monster jump along an arc. I don't remember this sort of math from school it's just been too long =/ .
- Use some sort of function built into Swift that can do this for me automatically (I did some research but most of it was either old Objective-C stuff, or looked insanely complicated).

Could someone point me in the right direction?

Thanks!

Answer

I don't know much about scene kit, but if you have a way to make your sprite travel across a Bezier path then a quadratic (not cubic) Bezier path is exactly what you need. A parabola is a quadratic curve, so it should be easy to model with a Quadratic bezier (2 end points plus a single control point.)

Creating a quadratic bezier curve is trivially easy. you specify a start and end point and a control point, and the curve follows the V defined by those 3 points.

Source (Stackoverflow)