B4J Tutorial Bouncing Balls

Enjoy!

Comment/uncomment the code in class Ball(move) and see gravity, friction, damping changing the behavior of the balls.

Public Sub move
  
'    Dim damp As Double = 0.99      'was 0.99
'    Dim friction As Double = 0.97   'was 0.97
'    Dim gravity As Double = 0.01
'    vx = vx * damp
'    vy = vy * damp
'    vy = vy + gravity
'    If ((rx + vx * friction) + radius > cv.Width) Then vx = -1 * vx
'    If ((rx + vx * friction) - radius < 0) Then vx = -1 * vx
'    If ((ry + vy * friction) + radius > cv.Height) Then vy = -1 * vy
'    If ((ry + vy * friction) - radius < 0) Then vy = -1 * vy
'    rx = rx + vx * friction
'    ry = ry + vy * friction
  
    If ((rx + vx) + radius > cv.Width) Then bounceOffVerticalWall
    If ((rx + vx) - radius < cv.Left) Then bounceOffVerticalWall
    If ((ry + vy) + radius > cv.Height) Then bounceOffHorizontalWall
    If ((ry + vy) - radius < cv.Top) Then bounceOffHorizontalWall
    rx = rx + vx
    ry = ry + vy
End Sub

Change the number of balls( Dim b(100)) to whatever you like:

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
    Private xui As XUI

    Private cv As Canvas
    Dim b(100) As Ball
  
    Dim t As Timer
  
End Sub

 

[kimstudio]

There may be not needed to do cv.ClearRect() before cv.DrawRect().

 

[BlueVision]

Crazy. Johan, reminded me immediately to this (THANK YOU!):

AMIGA - Boing Ball

 

[kimstudio]

AMIGA - Boing Ball

The Boing Ball is relatively complicated with rotation, texture and shadow effect, which I realized in my fantasy player: https://www.b4x.com/android/forum/threads/bx32-fantasy-player.139906/#content