'ViewportMatrix einstellen
  With DX7
    .IdentityMatrix View3DMatrix
    .ViewMatrix View3DMatrix, RVector(0, 0, 0), _
        RVector(0, 0, 1000), RVector(0, 1, 0), 0
  End With
  Device.SetTransform D3DTRANSFORMSTATE_VIEW, View3DMatrix

  'neuen Ursprung der ViewportMatrix einstellen
  Device.GetTransform D3DTRANSFORMSTATE_VIEW, View3DMatrix
  TranslateMatrix View3DMatrix, RVector( _
        PLAYER.x * -1, PLAYER.y * -1, PLAYER.z * -1)
  Device.SetTransform D3DTRANSFORMSTATE_VIEW, View3DMatrix

  Do
    PLAYER.TurnHor = 0#
    PLAYER.TurnVer = 0#
    PLAYER.Move = MOVE_NONE
    DIModule.CheckInput
    DIModule.CheckMouse
    With PLAYER
      'y-Achse rotieren
      If .TurnHor <> 0 Then
        .AngleY = .AngleY + (.TurnHor / 5)
        .Move = .Move Or MOVE_TURN
        If .AngleY < 0 Then
            .AngleY = 360 + .AngleY
        ElseIf .AngleY > 360 Then
            .AngleY = .AngleY - 360
        End If
      End If
      'x-Achse rotieren
      If .TurnVer <> 0 Then
        .AngleX = .AngleX + (.TurnVer / 10)
        If .AngleX > 50 Then .AngleX = 50
        If .AngleX < -50 Then .AngleX = -50
        .Move = .Move Or MOVE_TURN
      End If
    End With

    'hat sich der Spieler überhaupt bewegt ?
    If PLAYER.Move <> MOVE_NONE Then
      'neue Spielerposition berechnen
      CalculateViewStartPos
      'Matrix-Ursprung auf Spielerposition setzen
      TranslateMatrix myTranslateMatrix, RVector( _
            PLAYER.x * -1, PLAYER.y * -1, PLAYER.z * -1)
      'Matrix Y-Rotation
      RotateYMatrix myYMatrix, PLAYER.AngleY * PI / 180
      'Matrix X-Rotation
      RotateXMatrix myXMatrix, PLAYER.AngleX * PI / 180
      'Matrizen zusammenführen
      myNewMatrix = RetMatrixMult(myTranslateMatrix, myYMatrix)
      View3DMatrix = RetMatrixMult(myNewMatrix, myXMatrix)
      'Transformation der ViewPortMatrix durchführen
      Device.SetTransform D3DTRANSFORMSTATE_VIEW, View3DMatrix
    End If
    'Szene rendern
    Render3D
    BackBuffer.BltFast 394, 294, bmpCross, recCross, _
        DDBLTFAST_WAIT Or DDBLTFAST_SRCCOLORKEY
    PrimarySurface.Flip BackBuffer, DDFLIP_WAIT
    DoEvents
  Loop While Running

Private Sub CalculateViewStartPos()
  Dim px As Single
  Dim pz As Single

  If (PLAYER.Move And MOVE_FORE) = MOVE_FORE Then
    px = Sin((PLAYER.AngleY * (PI / 180))) / 2
    pz = Cos((PLAYER.AngleY * (PI / 180))) / 2
    PLAYER.x = PLAYER.x + px
    PLAYER.z = PLAYER.z + pz
  End If
  If (PLAYER.Move And MOVE_BACK) = MOVE_BACK Then
    px = -Sin((PLAYER.AngleY * (PI / 180))) / 2
    pz = -Cos((PLAYER.AngleY * (PI / 180))) / 2
    PLAYER.x = PLAYER.x + px
    PLAYER.z = PLAYER.z + pz
  End If
  If (PLAYER.Move And MOVE_LEFT) = MOVE_LEFT Then
    px = Sin((PLAYER.AngleY * (PI / 180))) / 2
    pz = -Cos((PLAYER.AngleY * (PI / 180))) / 2
    PLAYER.x = PLAYER.x - pz * -1
    PLAYER.z = PLAYER.z - px * -1
  End If
  If (PLAYER.Move And MOVE_RIGHT) = MOVE_RIGHT Then
    px = Sin((PLAYER.AngleY * (PI / 180))) / 2
    pz = -Cos((PLAYER.AngleY * (PI / 180))) / 2
    PLAYER.x = PLAYER.x + pz * -1
    PLAYER.z = PLAYER.z + px * -1
  End If
End Sub

Public Sub TranslateMatrix(m As D3DMATRIX, v As D3DVECTOR)
  m.rc41 = v.x
  m.rc42 = v.y
  m.rc43 = v.z
End Sub

Public Function RetMatrixMult(a As D3DMATRIX, b As D3DMATRIX) _
      As D3DMATRIX

  Dim ret As D3DMATRIX

  ret.rc11 = b.rc11 * a.rc11 + b.rc21 * a.rc12 + _
             b.rc31 * a.rc13 + b.rc41 * a.rc14
  ret.rc12 = b.rc12 * a.rc11 + b.rc22 * a.rc12 + _
             b.rc32 * a.rc13 + b.rc42 * a.rc14
  ret.rc13 = b.rc13 * a.rc11 + b.rc23 * a.rc12 + _
             b.rc33 * a.rc13 + b.rc43 * a.rc14
  ret.rc14 = b.rc14 * a.rc11 + b.rc24 * a.rc12 + _
             b.rc34 * a.rc13 + b.rc44 * a.rc14
  ret.rc21 = b.rc11 * a.rc21 + b.rc21 * a.rc22 + _
             b.rc31 * a.rc23 + b.rc41 * a.rc24
  ret.rc22 = b.rc12 * a.rc21 + b.rc22 * a.rc22 + _
             b.rc32 * a.rc23 + b.rc42 * a.rc24
  ret.rc23 = b.rc13 * a.rc21 + b.rc23 * a.rc22 + _
             b.rc33 * a.rc23 + b.rc43 * a.rc24
  ret.rc24 = b.rc14 * a.rc21 + b.rc24 * a.rc22 + _
             b.rc34 * a.rc23 + b.rc44 * a.rc24
  ret.rc31 = b.rc11 * a.rc31 + b.rc21 * a.rc32 + _
             b.rc31 * a.rc33 + b.rc41 * a.rc34
  ret.rc32 = b.rc12 * a.rc31 + b.rc22 * a.rc32 + _
             b.rc32 * a.rc33 + b.rc42 * a.rc34
  ret.rc33 = b.rc13 * a.rc31 + b.rc23 * a.rc32 + _
             b.rc33 * a.rc33 + b.rc43 * a.rc34
  ret.rc34 = b.rc14 * a.rc31 + b.rc24 * a.rc32 + _
             b.rc34 * a.rc33 + b.rc44 * a.rc34
  ret.rc41 = b.rc11 * a.rc41 + b.rc21 * a.rc42 + _
             b.rc31 * a.rc43 + b.rc41 * a.rc44
  ret.rc42 = b.rc12 * a.rc41 + b.rc22 * a.rc42 + _
             b.rc32 * a.rc43 + b.rc42 * a.rc44
  ret.rc43 = b.rc13 * a.rc41 + b.rc23 * a.rc42 + _
             b.rc33 * a.rc43 + b.rc43 * a.rc44
  ret.rc44 = b.rc14 * a.rc41 + b.rc24 * a.rc42 + _
             b.rc34 * a.rc43 + b.rc44 * a.rc44

  RetMatrixMult = ret
End Function

Public Sub RotateYMatrix(ByRef ret As D3DMATRIX, _
      ByVal rads As Single)
  Dim cosine As Single
  Dim sine As Single

  cosine = Cos(rads)
  sine = Sin(rads)

  ret.rc11 = cosine
  ret.rc33 = cosine
  ret.rc13 = sine
  ret.rc31 = -sine
End Sub

Public Sub RotateXMatrix(ByRef ret As D3DMATRIX, _
      ByVal rads As Single)
  Dim cosine As Single
  Dim sine As Single

  cosine = Cos(rads)
  sine = Sin(rads)

  ret.rc22 = cosine
  ret.rc33 = cosine
  ret.rc23 = -sine
  ret.rc32 = sine
End Sub

Public Function RVector(ByVal x As Single, ByVal y As Single, _
      ByVal z As Single) As D3DVECTOR
  Dim v As D3DVECTOR

  v.x = x
  v.y = y
  v.z = z
  RVector = v
End Function