I want to make a trajectory line of little balls of where the object is going to go after an impulse, sort of like what is in Angry Birds. I did some research and it seems that the physics in spriteKit are calculated just as in real life with si units and other stuff. Using the displacement formula ∆x = Vi∆t + 1/2a∆t^2 i used this formula to set the position of nine balls of where the object will be after the impulse.
This is what I have tried so far:
func calculateTrajectory(mass: CGFloat, force1: CGFloat, force2: CGFloat){
for i in 0...8{
var x = CGFloat()
var y = CGFloat()
let a1 = CGFloat(force1/mass)//I am taking the force applied to the object and calculating the acceleration from that
let a2 = CGFloat((force1/mass) - 10)//I am subtracting 10 for y because of the -10m/s/s of gravity
let t = CGFloat((i/16)^2)//I am taking the number that the ball is in the line and dividing it by 16 so the line can show where the object will be from 0-0.5 secnds
x = 0.5 * a1 * t
y = 0.5 * a2 * t
trajectory.copiedNodes[i].position = CGPoint(x:ball.position.x + x, y: ball.position.y + y)
}
}
I also use this in touches moved to do a drag back sling shot sort of thing.
calculateTrajectory(mass: (ball.physicsBody?.mass)!, force1: startPositionDrag.x - movedLocation.x, force2: startPositionDrag.y - movedLocation.y)
The force for calculation is the same as impulse that I will use to shoot the ball in touches ended:
ball.physicsBody?.applyImpulse(CGVector(dx:startPositionDrag.x - endPositionDrag.x, dy:startPositionDrag.y - endPositionDrag.y ))
When I calculate this the balls are not close to where the object goes, and when I make the time change for the balls a shorter time amount by dividing i by more, the balls get farther apart even though I am calculating their positions after less time. Is there any way I am doing this wrong? Are my conversions to CGFloat wrong? Please help me.
