OpenGL examples

[TempodiBasic]

The following is a demonstration of how to texture a cube with different textures from different sides. Notice the ever-repeating _glTexCoord2f, followed by _glVertex3f... over and over again. That's literally says - use  field! This way it's better for understanding, but in practice I would rather create a data file with the coordinates and then compile the whole thing in a loop using only these two commands.

Try applying a texture with transparency to one position, it's quite interesting. Don't forget that even in this case you can mix color as in the previous example.


Do not forgot to change texture file names!

Code: (Select All)

Type GL_Loader
    PointerGL As Long
    TextureName As String
End Type
ReDim Shared GLL(0) As GL_Loader, t As Long
Dim Shared GL_InitInfo As _Byte
Dim Shared ExitSignal As _Byte

_Title "Use texture!"
Screen _NewImage(1024, 768, 32)




Do
    If ExitSignal Then System
    _Limit 40
Loop

Sub _GL ()
    Static Xrot, Yrot, Zrot, t


    t1 = LoadTexture("Phoenix.png") 'function load texture from valid file and return OpenGL Handle for this texture,
    t2 = LoadTexture("X.png")
    t3 = LoadTexture("cat.gif")
    t4 = LoadTexture("banan.gif")
    t5 = LoadTexture("dum03.jpg")
    t6 = LoadTexture("new sob.gif")



    '                             if handle exists, return it and do not next.
    Init2


    _glClear _GL_COLOR_BUFFER_BIT And _GL_DEPTH_BUFFER_BIT 'Clear screen and depth buffer


    _glMatrixMode _GL_PROJECTION '                          Set projection matrix  - TRY comment this five rows and then run it. Black screen occur. For view just something then must be depth set to -1 (Z parameter in _glTranslateF)
    _glLoadIdentity '();// Reset matice
    _gluPerspective 90.0F, _Width / _Height, 0.1F, 100.0F ' Perspective calculation
    _glMatrixMode _GL_MODELVIEW '                           set modelview matrix
    _glLoadIdentity

    _glTranslatef 0.0F, 0.0F, -5F 'Shift to depth - without projection matrix settings if Z is -5 just black screen occur!

    _glRotatef Xrot, 1.0F, 0.0F, 0.0F 'rotation in axis X

    _glRotatef Yrot, 0.0F, 1.0F, 0.0F '                 Y

    _glRotatef Zrot, 0.0F, 0.0F, 1.0F '                 Z


    _glBindTexture _GL_TEXTURE_2D, t1 'set texture - in this case phoenix logo to this wall

    _glBegin _GL_QUADS

    'Front Wall

    _glTexCoord2f 0.0F, 0.0F: _glVertex3f -1.0F, -1.0F, 1.0F

    _glTexCoord2f 1.0F, 0.0F: _glVertex3f 1.0F, -1.0F, 1.0F

    _glTexCoord2f 1.0F, 1.0F: _glVertex3f 1.0F, 1.0F, 1.0F

    _glTexCoord2f 0.0F, 1.0F: _glVertex3f -1.0F, 1.0F, 1.0F

    _glEnd '<---------------- for more texture FIRST MUST BE _glEnd used and then



    _glBindTexture _GL_TEXTURE_2D, t2 'set character "X" as texture to this wall

    _glBegin _GL_QUADS '<-----------  after new texture settings, continue

    ' Rear Wall

    _glTexCoord2f 1.0F, 0.0F: _glVertex3f -1.0F, -1.0F, -1.0F

    _glTexCoord2f 1.0F, 1.0F: _glVertex3f -1.0F, 1.0F, -1.0F

    _glTexCoord2f 0.0F, 1.0F: _glVertex3f 1.0F, 1.0F, -1.0F

    _glTexCoord2f 0.0F, 0.0F: _glVertex3f 1.0F, -1.0F, -1.0F

    _glEnd



    _glBindTexture _GL_TEXTURE_2D, t3 'set cat image as texture to this wall

    _glBegin _GL_QUADS '<-----------  after new texture settings, continue

    ' Upper Wall

    _glTexCoord2f 0.0F, 1.0F: _glVertex3f -1.0F, 1.0F, -1.0F

    _glTexCoord2f 0.0F, 0.0F: _glVertex3f -1.0F, 1.0F, 1.0F

    _glTexCoord2f 1.0F, 0.0F: _glVertex3f 1.0F, 1.0F, 1.0F

    _glTexCoord2f 1.0F, 1.0F: _glVertex3f 1.0F, 1.0F, -1.0

    _glEnd


    _glBindTexture _GL_TEXTURE_2D, t4 'set banana image as texture to this wall

    _glBegin _GL_QUADS '<-----------  after new texture settings, continue

    ' Bottom Wall

    _glTexCoord2f 1.0F, 1.0F: _glVertex3f -1.0F, -1.0F, -1.0F

    _glTexCoord2f 0.0F, 1.0F: _glVertex3f 1.0F, -1.0F, -1.0F

    _glTexCoord2f 0.0F, 0.0F: _glVertex3f 1.0F, -1.0F, 1.0F

    _glTexCoord2f 1.0F, 0.0F: _glVertex3f -1.0F, -1.0F, 1.0F

    _glEnd


    _glBindTexture _GL_TEXTURE_2D, t5 'set house image as texture to this wall

    _glBegin _GL_QUADS '<-----------  after new texture settings, continue

    ' Right Wall

    _glTexCoord2f 1.0F, 0.0F: _glVertex3f 1.0F, -1.0F, -1.0F

    _glTexCoord2f 1.0F, 1.0F: _glVertex3f 1.0F, 1.0F, -1.0F

    _glTexCoord2f 0.0F, 1.0F: _glVertex3f 1.0F, 1.0F, 1.0F

    _glTexCoord2f 0.0F, 0.0F: _glVertex3f 1.0F, -1.0F, 1.0F

    _glEnd


    _glBindTexture _GL_TEXTURE_2D, t6 'set reindeer as texture to this wall

    _glBegin _GL_QUADS '<-----------  after new texture settings, continue

    ' Left Wall

    _glTexCoord2f 0.0F, 0.0F: _glVertex3f -1.0F, -1.0F, -1.0F

    _glTexCoord2f 1.0F, 0.0F: _glVertex3f -1.0F, -1.0F, 1.0F

    _glTexCoord2f 1.0F, 1.0F: _glVertex3f -1.0F, 1.0F, 1.0F

    _glTexCoord2f 0.0F, 1.0F: _glVertex3f -1.0F, 1.0F, -1.0F

    _glEnd



    Xrot = Xrot + 0.3F

    Yrot = Yrot + 0.2F

    Zrot = Zrot + 0.4F





    If _Exit Then
        DeleteTexture t 'if program end, first free texture from memory, then exit from GL and return to main loop
        _glClear _GL_COLOR_BUFFER_BIT
        ExitSignal = Not 0
        Exit Sub
    End If

End Sub

Sub GL_Init
    If GL_InitInfo = 0 Then
        '   _glViewport 0, 0, _Width, _Height
        GL_InitInfo = 1
    End If
End Sub

Sub Init2
    _glEnable _GL_TEXTURE_2D 'allow texture maping

    _glShadeModel _GL_SMOOTH ' smooth

    _glClearColor 0.1F, 0.1F, 0.1F, 0.5F 'Black background

    _glClearDepth 1.0F '       depth buffer settings

    _glEnable _GL_DEPTH_TEST ' Allow depth testing - try comment it and the run program. Object is then very deformed.

    _glDepthFunc _GL_LEQUAL '  Depth testing type

    _glHint _GL_PERSPECTIVE_CORRECTION_HINT, _GL_NICEST ' best perspective projection
End Sub

Sub DeleteTexture (nr As Long)
    For P = LBound(GLL) To UBound(GLL)
        If GLL(P).PointerGL = nr Then
            Dim DEL As Long
            DEL = GLL(P).PointerGL
            _glDeleteTextures 1, _Offset(DEL)
            Exit Sub
        End If
    Next
End Sub


Function LoadTexture (image As String)
    If GL_InitInfo = 0 Then GL_Init
    If _FileExists(image) Then
        TT = 0
        Do Until TT = UBound(GLL)
            If GLL(TT).TextureName = image$ Then
                LoadTexture = GLL(TT).PointerGL 'prevent memory leak loading next and next texture again and angain...
                Exit Function
            End If
            TT = TT + 1
        Loop


        t = t + 1


        tex& = _LoadImage(image$, 32)
        texinv& = _NewImage(_Width(tex&), _Height(tex&), 32)

        _PutImage (0, _Height(tex&) - 1)-(_Width(tex&) - 1, 0), tex&, texinv&
        _FreeImage tex&
        Dim Texture As Long
        _glGenTextures 1, _Offset(Texture) 'generate our texture handle    (reserve place in memory for new texture)
        _glBindTexture _GL_TEXTURE_2D, Texture 'select our texture handle  (set this texture for use)
        Dim m As _MEM
        m = _MemImage(texinv&)
        _glTexImage2D _GL_TEXTURE_2D, 0, _GL_RGB, _Width(texinv&), _Height(texinv&), 0, _GL_BGRA_EXT, _GL_UNSIGNED_BYTE, m.OFFSET


        'glTexImage2D(GL_TEXTURE_2D, 0, 3, TextureImage[0]->sizeX, TextureImage[0]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);

        U = UBound(GLL)
        GLL(U).PointerGL = Texture
        GLL(U).TextureName = image$
        ReDim _Preserve GLL(U + 1) As GL_Loader

        _MemFree m

        'set our texture wrapping
        _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_WRAP_S, _GL_REPEAT
        _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_WRAP_T, _GL_REPEAT

        'set out texture filtering
        _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_MAG_FILTER, _GL_LINEAR 'for scaling up
        _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_MIN_FILTER, _GL_LINEAR 'for scaling down


    Else
        Print "LoadTexture Error: "; image$; " - file not found."
    End If
    LoadTexture = Texture
End Function

Hi Petr,
where are the images for texture that you load?

are they these following?
tiger
bird
cat
horse
dog
eagle