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Thread: Example: Section 8.2 (page 261), A little Gravity!

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    Example: Section 8.2 (page 261), A little Gravity!

    [code=thinbasic]
    ' Example: Section 8.2 (page 261), A little Gravity!

    ' From Stan Blank's Book:
    ' "Python Programming in OpenGL
    ' "A Graphical Approach to Programming

    ' Converted by Michael Clease (Stolen timing ideas from Petr..hehe)
    ' Last modified: February 27, 2010

    Uses "TBGL"

    ' Handle for our window
    Global hWnd As DWord
    Global Width As Long
    Global Height As Long
    Global x,y As Double
    Global dx,dy As Double
    Global anim As Long
    Global axrng As Double
    Global hvel As Double
    Global vvel As Double
    Global radius As Double
    Global xborder As Double
    Global yborder As Double
    Global dtime As Double
    Dim Title As String Value "A little Gravity! - Press 'A' to start, 'S' to stop or 'Esc' to quit"
    width = 600
    height = 600
    '
    ' Create and show window
    hWnd = TBGL_CreateWindowEx(Title, Width, Height, 32, %TBGL_WS_WINDOWED )
    TBGL_ShowWindow

    Init()'Anim,x,y,dx,dy,axrng)
    ' Define "Callback" to be fired + that it should be fired each 10ms
    TBGL_BindPeriodicFunction(hWnd, "PlotFunc", 10)

    ' -- Once the command below is executed, further script execution
    ' -- is halted and only periodic calling of the bound function is performed
    TBGL_ProcessPeriodicFunction(hWnd)

    TBGL_DestroyWindow

    Sub Init() 'ByRef anim,ByRef x,ByRef y,ByRef dx,ByRef dy,axrng)
    '# initial position of the ball
    x = -0.67
    y = 0.34
    dtime = 0.005
    radius = 0.1
    hvel = 0.75
    vvel = 3.0
    '# Direction "sign" of the ball's motion
    dx = 1
    dy = 1
    '# Window dimensions
    xborder = 1.0
    yborder = 1.0
    axrng = 1.0
    '# No animation To start
    anim = 0
    TBGL_Color(255,0,0)
    TBGL_BackColor(0,0,0)
    ' Resets status of all keys
    TBGL_ResetKeyState()
    End Sub

    Sub PlotFunc()
    ' -- Which window is calling?
    Local hWnd As DWord = TBGL_CallingWindow

    If Anim Then
    TBGL_ClearFrame
    TBGL_RenderMatrix2D(-axrng, -axrng, axrng, axrng)

    vvel = vvel - 9.8*dtime
    y += vvel*dtime
    If y <= (-axrng + radius) Then y = -axrng + radius
    x += hvel*dtime

    TBGL_PushMatrix
    TBGL_Translate(x,y,0)
    TBGL_Sphere(Radius)
    TBGL_PopMatrix
    If x >= (xborder - radius) Or x <= (-xborder + radius) Then hvel = -1*hvel
    If y >= (yborder - radius) Or y <= (-yborder + radius) Then vvel = -1*vvel

    TBGL_DrawFrame
    EndIf
    If TBGL_GetWindowKeyState(hWnd, %VK_A) Then Anim = 1
    If TBGL_GetWindowKeyState(hWnd, %VK_S) Then Anim = 0

    ' ESCAPE key to disable callback
    If TBGL_GetWindowKeyState(hWnd, %VK_ESCAPE) Then
    TBGL_UnBindPeriodicFunction( hWnd )
    Exit Sub
    End If

    End Sub

    [/code]
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  2. #2
    thinBasic MVPs kryton9's Avatar
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    Re: Example: Section 8.2 (page 261), A little Gravity!

    Another really useful function and can be used in so many game types. This is really great having you guys join in on the conversions and doing such a great job!
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