'--- Im Erstellungs-Bereich vom Direct3D ---
  'ViewportMatrix einstellen
  'Dieser wird definiert durch einen Ausgangspunkt (auch
  'Eye Point genannt), einer Orientierung (auch LookAt genannt)
  'und der Angabe wo "oben" ist (Standard ist Y, die Achse, die
  '"oben" ist).
  D3DXMatrixIdentity View3DMatrix
  D3DXMatrixLookAtLH View3DMatrix, vec3(0, 0, 0), _
            vec3(0, 0, 1000), vec3(0, 1, 0)
  gD3DDevice8.SetTransform D3DTS_VIEW, View3DMatrix

  'Neuen Ursprung der Viewport-Matrix einstellen
  gD3DDevice8.GetTransform D3DTS_VIEW, View3DMatrix
  TranslateMatrix View3DMatrix, _
        vec3(PLAYER.X * -1, PLAYER.Y * -1, PLAYER.Z * -1)
  gD3DDevice8.SetTransform D3DTS_VIEW, View3DMatrix

'--- Game-Loop ---
  Do
    PLAYER.TurnHor = 0#
    PLAYER.TurnVer = 0#
    PLAYER.Move = MOVE_NONE

    'Prüfen auf Anwender-Eingabe
    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, _
            vec3(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
      gD3DDevice8.SetTransform D3DTS_VIEW, View3DMatrix
    End If

    '3D Szene rendern
    Render3D
    DoEvents
  Loop While running

'--- Berechnungen ---
  'Position des Spielers berechnen
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)))
    pz = Cos((PLAYER.AngleY * (PI / 180)))
    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)))
    pz = -Cos((PLAYER.AngleY * (PI / 180)))
    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)))
    pz = -Cos((PLAYER.AngleY * (PI / 180)))
    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)))
    pz = -Cos((PLAYER.AngleY * (PI / 180)))
    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.m41 = v.X
  m.m42 = v.Y
  m.m43 = v.Z
End Sub

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

  ret.m11 = b.m11 * a.m11 + b.m21 * a.m12 + b.m31 * a.m13 + _
      b.m41 * a.m14
  ret.m12 = b.m12 * a.m11 + b.m22 * a.m12 + b.m32 * a.m13 + _
      b.m42 * a.m14
  ret.m13 = b.m13 * a.m11 + b.m23 * a.m12 + b.m33 * a.m13 + _
      b.m43 * a.m14
  ret.m14 = b.m14 * a.m11 + b.m24 * a.m12 + b.m34 * a.m13 + _
      b.m44 * a.m14
  ret.m21 = b.m11 * a.m21 + b.m21 * a.m22 + b.m31 * a.m23 + _
      b.m41 * a.m24
  ret.m22 = b.m12 * a.m21 + b.m22 * a.m22 + b.m32 * a.m23 + _
      b.m42 * a.m24
  ret.m23 = b.m13 * a.m21 + b.m23 * a.m22 + b.m33 * a.m23 + _
      b.m43 * a.m24
  ret.m24 = b.m14 * a.m21 + b.m24 * a.m22 + b.m34 * a.m23 + _
      b.m44 * a.m24
  ret.m31 = b.m11 * a.m31 + b.m21 * a.m32 + b.m31 * a.m33 + _
      b.m41 * a.m34
  ret.m32 = b.m12 * a.m31 + b.m22 * a.m32 + b.m32 * a.m33 + _
      b.m42 * a.m34
  ret.m33 = b.m13 * a.m31 + b.m23 * a.m32 + b.m33 * a.m33 + _
      b.m43 * a.m34
  ret.m34 = b.m14 * a.m31 + b.m24 * a.m32 + b.m34 * a.m33 + _
      b.m44 * a.m34
  ret.m41 = b.m11 * a.m41 + b.m21 * a.m42 + b.m31 * a.m43 + _
      b.m41 * a.m44
  ret.m42 = b.m12 * a.m41 + b.m22 * a.m42 + b.m32 * a.m43 + _
      b.m42 * a.m44
  ret.m43 = b.m13 * a.m41 + b.m23 * a.m42 + b.m33 * a.m43 + _
      b.m43 * a.m44
  ret.m44 = b.m14 * a.m41 + b.m24 * a.m42 + b.m34 * a.m43 + _
      b.m44 * a.m44

  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.m11 = cosine
  ret.m33 = cosine
  ret.m13 = sine
  ret.m31 = -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.m22 = cosine
  ret.m33 = cosine
  ret.m23 = -sine
  ret.m32 = sine
End Sub

'Hilfsfunktion - einen D3DVektor erzeugen
Public Function vec3(X As Single, Y As Single, Z As Single) _
        As D3DVECTOR
  vec3.X = X
  vec3.Y = Y
  vec3.Z = Z
End Function