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Creating a Screen Saver with DirectX 8 and VB, Part 2: DirectX

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In the conclusion of his two-part series, Keith Sink explains how to write the DirectX code in a VB project to make a screen saver animate a scene.
Keith Sink is the author of DirectX 8 and Visual Basic Development (Sams, 2001, ISBN 0-672-32225-0).
From the author of

Creating the Animation

Source code can be found here.

To create the animation that will be involved in your project (see part 1 of this two-part series), you need to initialize the DirectX graphics objects and begin looping through your animation. The following steps do this:

  1. To create graphics in DirectX, you need a DirectX8 core object, a Direct3D8 object, a Direct3DDevice8 object that represents the graphics card, a D3DX8 helper object, and two textures (one for the snow scene and one for the background). You'll also be using vertices as the canvas for this scene; therefore, you have to define a custom class called CUSTOMVERTEX. Notice in this code sample that you'll be using DirectInput8. DirectInput8 monitors the keyboard and mouse for movement and deactivates the screen saver if movement is detected from the user. Here's the code:

    Dim oDX As DirectX8           ' The core DirectX object
    Dim oD3D As Direct3D8          ' The core Direct3D object
    Dim oD3DDevice As Direct3DDevice8    ' This initializes the 3D video card.
    Dim oD3DX As D3DX8            ' Additional Direct3D class libraries
    Dim oD3DT As Direct3DTexture8      ' Background(snowman) texture
    Dim oD3DT2 As Direct3DTexture8      ' Flake texture
    Dim oDI As DirectInput8         ' DirectInput object(for keyboard and mouse)
    Dim oDIDevKeyboard As DirectInputDevice8 ' Keyboard Device
    Dim oDIStateKeyboard As DIKEYBOARDSTATE ' Keyboard State
    Dim oDIDevMouse As DirectInputDevice8  ' Mouse Device
    Dim oDIStateMouse As DIMOUSESTATE    ' Mouse State
    
    Public bRunning As Boolean        ' Controls the execution loop
    Public lNumberOfFlakes As Integer
    Dim SnowPileX(640) As Integer      ' For tracking snowpile
    Public lLastMouseX As Long
    Public lLastMouseY As Long
    
    Private Type FlakeType
     PositionX As Single
     PositionY As Single
     SpeedX As Single
     SpeedY As Single
    End Type
    
    Private Flakes() As FlakeType
    
    'This structure describes a custom vertex.
    Private Type CUSTOMVERTEX
      X As Single
      Y As Single
      Z As Single
      rhw As Single
      color As Long
      specular As Long
      tu As Single
      tv As Single
    End Type
    
    'Creates our two objects: The snowflake and the background.
    Dim TriStrip(0 To 3) As CUSTOMVERTEX  ' Background
    Dim TriStrip2(0 To 3) As CUSTOMVERTEX  ' SnowFlake
  2. After you have created the DirectX objects, you need to initialize them. This is done in the InitializeEnvironment function. In this function, the DirectX objects are initialized, colors are set, the display mode is set, render modes are set, textures for the snowman scene and snowflakes are loaded, and a call is made to initialize the vertices you'll be using:

    '*****************************************************************************
    '** ObjectName: InitializeEnvironment
    '**
    '** Description: This function does the following:
    '**         1. Initializes the DirectX, Direct3D, and D3DX8 objects.
    '**         2. Initializes and defines the transparency color.
    '**         3. Sets up a 640x480 24-bit display mode.
    '**         4. Sets up the Direct3D present parameters.
    '**         5. Creates and sets up a Direct3D device.
    '**         6. Sets up the renderstate and vertex shader of the device.
    '**         7. Creates the background and flake textures from files.
    '**         8. Calls the InitializeVertices function.
    '**
    '*****************************************************************************
    Public Function InitializeEnvironment() As Boolean
      On Error GoTo Err_InitializeEnvironment
    
      Dim iCount As Long
    
      Dim DispMode As D3DDISPLAYMODE     ' Display mode descriptor
      Dim oD3DWindow As D3DPRESENT_PARAMETERS ' Window or viewport that will
                          ' be used to display images.
      Dim lColorKeyVal As Long        ' Colorkey for transparency
    
      ' Setup your DirectX objects
      Set oDX = New DirectX8         ' Create your DirectX object
      Set oD3D = oDX.Direct3DCreate()     ' Create your Direct3D object from the DX object.
      Set oD3DX = New D3DX8          ' Additional Direct3D class libraries
      Set oDI = oDX.DirectInputCreate     ' Create your DirectInput object
      Set oDIDevKeyboard = oDI.CreateDevice("GUID_SysKeyboard") ' Create a DirectInput Keyboard Device
      Set oDIDevMouse = oDI.CreateDevice("GUID_SysMouse") ' Create a DirectInput Mouse Device
    
      ' Setup the Keyboard attributes
      oDIDevKeyboard.SetCommonDataFormat DIFORMAT_KEYBOARD
      oDIDevKeyboard.SetCooperativeLevel Me.hWnd, DISCL_BACKGROUND Or DISCL_NONEXCLUSIVE
    
      oDIDevKeyboard.Acquire ' Acquire the Keyboard device
    
      ' Setup the mouse attributes
      oDIDevMouse.SetCommonDataFormat DIFORMAT_MOUSE
      oDIDevMouse.SetCooperativeLevel Me.hWnd, DISCL_BACKGROUND Or DISCL_NONEXCLUSIVE
    
      oDIDevMouse.Acquire ' Acquire the Mouse device
    
      lColorKeyVal = &HFFFF0000        ' Red is the transparency color
    
      'hide the mouse cursor
      'ShowCursor 0
    
      With DispMode
        .Format = D3DFMT_R5G6B5       ' 24-bit RGB pixel format
        .Width = 640
        .Height = 480
      End With
    
      With oD3DWindow
        .SwapEffect = D3DSWAPEFFECT_FLIP  ' Type of flipping to use.
        .BackBufferCount = 1        ' 1 backbuffer
        .BackBufferFormat = DispMode.Format ' Display format
        .BackBufferHeight = 480
        .BackBufferWidth = 640
        .hDeviceWindow = frmMain.hWnd    ' Where to display the finished product.
      End With
    
      ' Creates the Direct3D hardware device
      Set oD3DDevice = oD3D.CreateDevice(D3DADAPTER_DEFAULT, _
                  D3DDEVTYPE_HAL, _
                  frmMain.hWnd, _
                  D3DCREATE_SOFTWARE_VERTEXPROCESSING, _
                  oD3DWindow)
    
      With oD3DDevice
    
        ' Setup the vertex shader
        .SetVertexShader D3DFVF_XYZRHW Or D3DFVF_TEX1 Or D3DFVF_DIFFUSE Or D3DFVF_SPECULAR
    
        ' Set render states for the device
        ' --------------------------------
        ' Source blend
        .SetRenderState D3DRS_SRCBLEND, D3DBLEND_SRCALPHA
        ' Destination blend
        .SetRenderState D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA
        ' Alpha blending
        .SetRenderState D3DRS_ALPHABLENDENABLE, True
      End With
    
      ' Load the snowman scene texture
      Set oD3DT = oD3DX.CreateTextureFromFile(oD3DDevice, _
          App.Path & "\snowman.bmp")
    
      ' Load the snowflake texture
      Set oD3DT2 = oD3DX.CreateTextureFromFileEx(oD3DDevice, _
          App.Path & "\flake.bmp", 2, 2, _
          D3DX_DEFAULT, 0, D3DFMT_UNKNOWN, _
          D3DPOOL_MANAGED, D3DX_FILTER_POINT, _
          D3DX_FILTER_POINT, lColorKeyVal, _
          ByVal 0, ByVal 0)
    
      ' Randomly choose the position of each flake on the screen.
      For iCount = 1 To lNumberOfFlakes
        With Flakes(iCount)
          .PositionX = 1 + Int(640 * Rnd()) '640 * Rnd
          .PositionY = 1 + Int(400 * Rnd()) '400 * Rnd
    
          'set and normalize Flake speed
          .SpeedX = 0.1
          .SpeedY = 0.3
        End With
      Next iCount
    
      ' Make sure the background vertices were created.
      If InitialiseVertices() = True Then
        InitializeEnvironment = True
        Exit Function
      End If
    
      Exit Function
    
    Err_InitializeEnvironment:
      MsgBox "Error Number Returned: " & Err.Number & " Error Message: " & Err.Description
      InitializeEnvironment = False
    End Function
  3. After all the variables have been initialized, you're ready to start animating (see the following code). This is done in the Animate subroutine. This subroutine makes a call to reposition the flakes. Then it clears the Direct3DDevice object. After it's clear, you can begin painting the device by using the BeginScene method. You then assign the background texture to the device. Then a call is made to draw each flake. After the "cel" of animation is assembled, you make a call to EndScene. This tells the device that there is no more drawing to be done. The final step is to call the Present method. Present forces the newly created cel of animation to the forefront. This process of assembling cels of animation and then showing them is one of the ways in which animation can be done in DirectX.

    '*****************************************************************************
    '** ObjectName: Animate
    '**
    '** Description: This subroutine does the following:
    '**         1. Clear the Direct3DDevice object.
    '**         2. Begin the render of the scene.
    '**         3. Assign a texture to the Direct3DDevice object(background).
    '**         4. Draw the trianglestrip for our background.
    '**         5. Assign a texture to the Direct3DDevice object(snowflake).
    '**         6. Draw the trianglestrip for our snowflake.
    '**         7. End the render of the scene.
    '**         8. Present this frame of animation to the screen.
    '**
    '*****************************************************************************
    Public Sub Animate()
    On Error GoTo err_Animate
    
      MoveFlake ' Move the snowflakes
    
      With oD3DDevice
        .Clear 0, ByVal 0, D3DCLEAR_TARGET, 0, 1#, 0 '//Clear the screen black
    
        .BeginScene ' Start drawing
    
          ' Draw background
          .SetTexture 0, oD3DT ' Use the background texture
          .DrawPrimitiveUP D3DPT_TRIANGLESTRIP, 2, TriStrip(0), Len(TriStrip(0))
    
          DrawFlakes
    
        .EndScene ' End drawing
        .ShowCursor 0
        .Present ByVal 0, ByVal 0, 0, ByVal 0
      End With
    
      Exit Sub
    err_Animate:
      If Err.Number = -2005530520 Then ' This error occurs when stopping the snowman.
        Err.Clear
        Resume Next
      Else
        MsgBox Err.Number & Err.Description & " Error in Animate Module."
        Err.Clear
        Resume Next
      End If
    
    End Sub
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