Physical ball

[u9]

So here is a ball you can grap and throw around using the mouse. Can anyone make this into a game of any kind? I dear you

P.s. The air friction is not so realistic. When the object gets lighter it still falls pretty fast to the ground.


' Physical ball simulation may 2007 by u9
' u9 4T kallnet D0T fo
'

' Forces declaration of variables
Option explicit

' --------------------------------------------------
' Classes
' --------------------------------------------------

' This is a 2 dimensional point or vector
class Point
  Public x
  Public y
 
  Public Sub class_initialize
     x = 0
     y = 0
  End Sub
 
  ' Length of the vector
  Public Function length()
     length = sqr( x*x + y*y )
  End Function
 
  ' Length of the vector in squared space
  Public Function lengthSQ()
     lengthSQ = x*x + y*y
  End Function
 
  Public Sub setLength( newLength )
     Dim curLength
     curLength = length()
     If curLength > 0 Then
        x = x * newLength / curLength
        y = y * newLength / curLength
     End If
  End Sub
End Class

class Object
 
  ' Physics parameters
  Public pos'ition
  Public vel'ocity
  Private tmpvel ' Temporary variable containing velocity
  Public acc'eleration
 
  Public mass
  Public size ' Radius of object
 
  Public Sub initialize( posx, posy, velx, vely, startMass, radius )
     Set pos = New Point : pos.x = posx : pos.y = posy
     Set vel = New Point : vel.x = velx : vel.y = vely
     Set tmpvel = New Point
     Set acc = New Point
     mass = startMass
     size = radius
  End Sub
 
  ' Methods
 
  ' Update physics. dt is change in time since last call. Formulas available at: http://en.wikipedia.org/wiki/Equations_of_motion
  Public Sub update( dt )
     tmpvel.x = vel.x + acc.x * dt
     tmpvel.y = vel.y + acc.y * dt
     
     ' Limit object speed if needed. Note: Comparison done in squared distances
     If tmpvel.lengthSQ() > OBJECT_MAX_VELOCITY^2 Then
        Call tmpvel.setLength( OBJECT_MAX_VELOCITY )
     End If
     
     pos.x = pos.x + 1/2 * (vel.x + tmpvel.x) * dt
     pos.y = pos.y + 1/2 * (vel.y + tmpvel.y) * dt
     
     vel.x = tmpvel.x
     vel.y = tmpvel.y
     
     acc.x = 0
     acc.y = 0
  End Sub
 
  ' Change acceleration of object by applying a force. Newton's second law of motion. F = ma
  Public Sub addForce( forcex, forcey )
     acc.x = acc.x + forcex / mass
     acc.y = acc.y + forcey / mass
  End Sub
 
  ' Apply acceleration directly to object. Good for adding gravity
  Public Sub addAcc( accx, accy )
     acc.x = acc.x + accx
     acc.y = acc.y + accy
  End Sub
End class



' --------------------------------------------------
' Program itself
' --------------------------------------------------

' Initialize needed sub-systems
Const WIDTH = 1024
Const HEIGHT = 768
Const BOUNCE_FRICTION = 0.85 ' How much velocity should get lost in a collision with edge of screen
Const OBJECT_MAX_VELOCITY = 1000 ' units/second
Const BALL_SIZE = 5
Const BALL_MASS = 100

Graphics.initialize WIDTH, HEIGHT, True
Key.initialize
Mouse.initialize
Timers.initialize


' Needed variables
Dim font           ' For writing text on screen
Dim myTimer        ' Timer index
Dim isRunning      ' False when user presses escape
Dim dt             ' Change in time between frames (delta-time)
Dim totalTime      ' Total elapsed time (updated every frame)
Dim canvas         ' canvas for rendering the game on (instead of using the screen)
Dim ball           ' The ball object to throw around :)

' Make a canvas for the motion blur effect (not so important)
canvas = graphics.createimage( WIDTH, HEIGHT )

' Populate variables
font = Graphics.createfont( "Courier new", 12 )
myTimer = Timers.create()
Timers.start myTimer
isRunning = True

Set ball = New Object
Call ball.initialize( mouse.x, mouse.y, 0, 0, BALL_MASS, BALL_SIZE )

' The main loop
Do While isRunning
 
  ' Get change in time since last call
  dt = Timers.splitTime( myTimer )
  totalTime = Timers.appTime( myTimer )
 
  ' Exit if window closed or escape pressed
  If Key.pressed(vk_escape) Or Key.pressed(vk_windowx) Then isRunning = False
 
  ' React on mouse
  mouse.update
  If Mouse.LeftButton Then
     ball.pos.x = mouse.x
     ball.pos.y = mouse.y
     ball.vel.x = -mouse.dx / dt ' These should not be negated but there is a bug in B2D v.1.7
     ball.vel.y = -mouse.dy / dt
  ElseIf Mouse.RightButton Then
  Else
     mouse.dx
     mouse.dy
  End If
 
  ' Update ball's position by moving it the required amount given the time passed
  Call ball.addAcc( 0, 9.8 * 100 ) ' 100 pixels i say here is 1 meter. Gravity constant is 9.8
 
  ' Air resistance by adding force in opposite direction of the velocity
  Call ball.addForce( -ball.vel.x, -ball.vel.y )
 
  ' Update ball physics
  Call ball.update( dt )
 
  ' Possible pre-calculation of ball bounciness (used if ball is on edge of screen)
  Dim newLength : newLength = ball.vel.length() * BOUNCE_FRICTION
 
  ' Avoid possible jittering when movement is very little
  If newLength < 45 Then
     newLength = 0
  End If
 
  ' Bounce ball at edge of screen
  If ball.pos.x < 0 Then
     ball.pos.x = -ball.pos.x
     ball.vel.x = -ball.vel.x
     ball.vel.setLength( newLength )
  ElseIf ball.pos.x >= WIDTH Then
     ball.pos.x = ball.pos.x - (ball.pos.x-WIDTH)
     ball.vel.x = -ball.vel.x
     ball.vel.setLength( newLength )
  End If
  If ball.pos.y < 0 Then
     ball.pos.y = -ball.pos.y
     ball.vel.y = -ball.vel.y
     ball.vel.setLength( newLength )
  ElseIf ball.pos.y >= HEIGHT Then
     ball.pos.y = ball.pos.y - (ball.pos.y-HEIGHT)
     ball.vel.y = -ball.vel.y
     ball.vel.setLength( newLength )
  End If
 
  ' Draw the circle to the canvas (instead of screen)
  graphics.renderimage canvas
  Graphics.setrect 0, 0, WIDTH, HEIGHT, argb(25,10,10,10)
  graphics.setcircle ball.pos.x, ball.pos.y, ball.size, argb(255,255,255,255)
  graphics.rendernormal
 
  ' Draw canvas on screen
  graphics.clear
  graphics.setimage canvas
 
  ' Write some user feedback
  Graphics.settext "FPS: " & graphics.fps & " (" & formatnumber( dt, 3 ) & ")", 10, 10, font, argb(255,255,255,255)
  Graphics.settext "Pos: " & formatnumber( ball.pos.x ) & "   " & formatnumber( ball.pos.y ), 10, 24, font, argb(255,255,255,255)
  Graphics.settext "Vel: " & formatnumber( ball.vel.x ) & "   " & formatnumber( ball.vel.y ), 10, 38, font, argb(255,255,255,255)
  Graphics.settext "100 pixels = 1 meter", 10, 52, font, argb(255,255,255,255)
 
  ' Display buffer on screen
  graphics.display
 
  Do
     system.processMessages
  Loop While totalTime + 0.01 > Timers.appTime( myTimer )
 
Loop

' Clean up
Mouse.terminate
Key.terminate
Graphics.terminate


[Guilect]

cognitivelabs.com/ball_bounce.htm