Bounce Example

>From: Bert Freudenberg <[hidden email]>
>Sent: Nov 20, 2014 9:52 AM
>To: "A friendly place to get answers to even the most basic questions about
> Squeak." <[hidden email]>
>Subject: Re: [Newbies] Bounce Example
>
>On 20.11.2014, at 04:14, <[hidden email]> <[hidden email]> wrote:
>
>> Hello,
>>
>>  
>> I once saw a workspace example which caused a morph to move along an arc in a realistic way - appearing to be affected by gravity. Possibly written by someone from Disney?  Now I search in vain to find it. Please give me a reference.
>
>Morphic is not really set up for workspace-style programming. It assumes you will create your own morph class and implement methods to specify behavior.
>
>It's certainly possible to do. But you will run into various problems that you wouldn't have if you did it properly.
>
>That said, try the following. Assuming constant mass and gravity, the acceleration is constant (since F = ma).
>
>m := Morph new openInWorld.
>m position: World center.
>speed := 5 @ 0. "move horizontally at start"
>acceleration := 0 @ 1. "accelerate downwards"
>move := [m owner ifNotNil: [
> "Acceleration is a 2nd-order (quadratic) function. Physics and Math FTW"
> speed := speed + acceleration. "accel is 1st derivative of speed"
> m position: m position + speed. "speed is 1st derivative of pos"
> m left < m owner left ifTrue: [speed := speed x abs @ speed y]. "bounce"
> m right > m owner right ifTrue: [speed := speed x abs negated @ speed y].
> m top < m owner top ifTrue: [speed := speed x @ speed y abs].
> m bottom > m owner bottom ifTrue: [speed := speed x @ speed y abs negated].
> (move future: 20) value. "repeat every 20ms"
>]].
>move value. "first step"
>
>For even more fun you could control the morph with a joystick:
>
> j := JoystickMorph new openInWorld.
>
>And insert this inside the move block:
>
> acceleration := (j leftRight @ j upDown negated) * 0.1.
>
>Have fun!
>
>- Bert -
>
>