[SOLVED]PingPong an Image?

[Omnikam]

Hey there, I'm having a problem with my code
I'm trying to move an image across the screen and then move it back, and repeat the procedure, so it move moves in a PingPong. My solution was to use a timer and have it set conditions using if/end   Unfortunately it doest work as expected, I'm not sure why because my code logic seem logical. Any help would be appreciated

Code Select Expand

InitSprite()
UseJPEGImageDecoder()
UsePNGImageDecoder()
InitKeyboard() 
Global timer= 1
a= 0
b= -1100
OpenScreen(800,600,32,"PBWINDOW")

wave = LoadSprite (#PB_Any, "wave.png")
Repeat

  ExamineKeyboard()   
TransparentSpriteColor(wave,#White)
ClearScreen($0)

DisplayTransparentSprite(wave, a,300)
DisplayTransparentSprite(wave,b,400)
If timer<900
  b=b+2
  timer=timer+1
  EndIf
  If timer>1200
    b=b-2
    timer = timer+1
    EndIf
    If timer=>2000
     timer=0
EndIf

 
FlipBuffers()

Until KeyboardPushed (#PB_Key_Escape)
End



[Rbz]

I don't have purebasic here, but try to use screen coordinates and a variable to control direction, something like this:

Code Select Expand


InitSprite()
UseJPEGImageDecoder()
UsePNGImageDecoder()
InitKeyboard() 
Global timer= 1

a = 0
b = 200
moveflag = 0

OpenScreen(800,600,32,"PBWINDOW")

wave = LoadSprite (#PB_Any, "wave.png")

Repeat

ExamineKeyboard()   
TransparentSpriteColor(wave,#White)
ClearScreen($0)

DisplayTransparentSprite(wave, a,300)
DisplayTransparentSprite(wave,b,400)


If moveflag=0
    b=b+2
 
    if b>500
        moveflag = 1
    EndIf
 
EndIf

If moveflag=1
    b=b-2

    if b<100
        moveflag = 0
    EndIf

EndIf
 
FlipBuffers()

Until KeyboardPushed (#PB_Key_Escape)
End



[Omnikam]

That was just what i was looking for, Thankyou. It`s easy to understand whats going on, so ill be able to
use it for lots of different applications
have good karma

[emook]

Here are some other ping pong routines that you may find useful.

The first is a ping pong using a procedure, everytime it is called the value is increased or decreased if it has reached its max :

#maxCount = 500

Code Select Expand

Procedure PingPong()
  Static _count = #maxCount - 1
  _count = (_count + 1) % (#maxCount << 1)
  ProcedureReturn Abs(_count - #maxCount)
EndProcedure

Repeat
  Debug PingPong()
  Delay (5)
ForEver

Then we have one which looks much more complex but has the benefit of being autonomous, and you can have multiple pong pongs being managed with the same procedure :

Code Select Expand

; With this one you can set a min, a max, and you can keep track of more then one ping-pong at the time.

Structure T_PINGPONG
min.i
max.i
counter.i
direction.i
EndStructure

Procedure.i PingPong (*p.T_PINGPONG)
  If *p\direction = 0
    *p\direction = 1
    *p\counter = *p\min
  Else
    *p\counter + *p\direction   
    If *p\counter = *p\min Or *p\counter = *p\max
        *p\direction = -*p\direction
    EndIf   
  EndIf   
  ProcedureReturn *p\counter
EndProcedure



;****************************
; DEMO
;****************************


Define pp1.T_PINGPONG
Define pp2.T_PINGPONG

pp1\min = 1
pp1\max = 10

pp2\min = -5
pp2\max =  5

Repeat
  Debug "pp1 = " + PingPong(@pp1) + ", pp2 = " + PingPong(@pp2) 
  Delay (500)
ForEver

And put into your demo, as you can see the logic loop is much simpler now  :

Code Select Expand

InitSprite()
UseJPEGImageDecoder()
UsePNGImageDecoder()
InitKeyboard() 
Global timer= 1

Structure T_PINGPONG
  min.i
  max.i
  counter.i
  direction.i
EndStructure

Procedure.i PingPong (*p.T_PINGPONG)
  If *p\direction = 0
    *p\direction = 1
    *p\counter = *p\min
  Else
    *p\counter + *p\direction   
    If *p\counter = *p\min Or *p\counter = *p\max
      *p\direction = -*p\direction
    EndIf   
  EndIf   
  ProcedureReturn *p\counter
EndProcedure

Define pp1.T_PINGPONG
Define pp2.T_PINGPONG

pp1\min = 0
pp1\max = 50

pp2\min = 0
pp2\max =  50


OpenScreen(800,600,32,"PBWINDOW")

wave = LoadSprite (#PB_Any, "wave.png")

Repeat
 
  ExamineKeyboard()   
  TransparentSpriteColor(wave,#White)
  ClearScreen($0)
 
  DisplayTransparentSprite(wave, 50-PingPong(@pp1)-100,300)
  DisplayTransparentSprite(wave,PingPong(@pp2)-50,400)
 
 
  FlipBuffers()
 
Until KeyboardPushed (#PB_Key_Escape)
End

[Omnikam]

Nice one Emook  Ill definatly have to study each example
Have good karma 
Okay i looked at them, Brilliant  very very handy