OpenGL examples

[Petr]

So I'm getting into the dark areas of OpenGL. The reason is - strange behavior.

Check out this program. This is lighting. The problem here is with gluBuild2DMipmaps. This is a type of texture filtering, when using with _GL_TEXTURE_MIN_FILTER in the _glTexParameteri command, the program either dies in a white screen, or the texture is not created and the object is then all white. There will be more and more such problems. I tried everything possible just to SOMEHOW get it running. Therefore, do not take this program as an example.

The library definition should be correct, but - it is possible that it is not.

Change the texture name on lines 82 to 84, I also changed the texture loader so that it is possible to load multiple textures with the same name, but in a way that takes into account the type of filter used, so a texture of the same name using the same filter is not loaded more than once.

Any insights, modifications, corrections, your modifications, everything is very welcome. Try making adjustments to the LightAmbient, LightDifuse and LightPosition fields, all your adjustments should affect the way the rotating cube is lit.



Perhaps one of you will find an effective way to solve the problem described above better.

Code: (Select All)

Declare CustomType Library
    Sub gluBuild2DMipmaps (BYVAL Target As _Unsigned Long, BYVAL iFormat As Long, BYVAL Wdth As Long, BYVAL Hght As Long, BYVAL format As _Unsigned Long, BYVAL typ As _Unsigned Long, BYVAL dat As _Offset)
End Declare


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

Dim Shared LightAmbient(3) As Single
LightAmbient(0) = 0.5
LightAmbient(1) = 0.5
LightAmbient(2) = 0.5
LightAmbient(3) = .1


Dim Shared LightDifuse(3) As Single
LightDifuse(0) = 1
LightDifuse(1) = 1
LightDifuse(2) = 1
LightDifuse(3) = 1

Dim Shared LightPosition(3) As Single
LightPosition(0) = 0
LightPosition(1) = 0
LightPosition(2) = 2
LightPosition(3) = 1

Dim Shared Textures(2) As Long, SetTexture, Light, Xrot, Yrot, Zdepth

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

SetTexture = 0
Light = -1
Xrot = .2
Yrot = .3
Zdepth = -5
Do
    i$ = InKey$
    Select Case UCase$(i$)
        Case "L"
            If LightTimer < Timer Then
                Light = Light * -1
                LightTimer = Timer + 1
            End If
        Case "F"
            SetTexture = SetTexture + 1
            If SetTexture > 2 Then SetTexture = 0
        Case "S" 'rotation in X axis
            Xrot = Xrot + .3
        Case "X"
            Xrot = Xrot - .3
        Case "C"
            Yrot = Yrot - .3
        Case "D"
            Yrot = Yrot + .3
        Case "G"
            Zdepth = Zdepth + .1
        Case "B"
            Zdepth = Zdepth - .1

    End Select

    If ExitSignal Then System
    _Limit 40
Loop

Sub _GL ()
    Static xr, yr, zrot
    Locate 2
    Print "Try keys L: Light on/off"
    Print "Set texture filtering: F"
    Print "Rotation speed in X axis: S, X"
    Print "Rotation speed in Y axis: C, D"
    Print "Set Depth: G, B"
    Textures(0) = LoadTexture("5b.jpg", 2) 'function load texture from valid file and return OpenGL Handle for this texture,
    Textures(1) = LoadTexture("5b.jpg", 1)
    Textures(2) = LoadTexture("5b.jpg", 0)


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

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

    _glRotatef yr, 0.0F, 1.0F, 0.0F '                Y

    _glRotatef zrot, 0.0F, 0.0F, 1.0F '              Z

    _glBindTexture _GL_TEXTURE_2D, Textures(SetTexture) 'set texture - in this case 1 texture for whole cube, 1 texture with 3 types of filtering

    _glBegin _GL_QUADS

    'Front Wall
    _glNormal3f 0.0F, 0.0F, 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, 1.0F

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

    ' Rear Wall
    _glNormal3f 0.0F, 0.0F, -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

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

    ' Upper Wall
    _glNormal3f 0.0F, 1.0F, 0.0F

    _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

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

    ' Bottom Wall

    _glNormal3f 0.0F, -1.0F, 0.0F

    _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

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

    ' Right Wall

    _glNormal3f 1.0F, 0.0F, 0.0F

    _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

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

    ' Left Wall

    _glNormal3f -1.0F, 0.0F, 0.0F

    _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, 1.0F

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

    _glEnd



    zrot = zrot + 0.4F
    xr = xr + Xrot
    yr = yr + Yrot




    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

    _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

    'dodatek pro lighting

    _glLightfv _GL_LIGHT1, _GL_AMBIENT, _Offset(LightAmbient!()) 'ambient light
    _glLightfv _GL_LIGHT1, _GL_DIFFUSE, _Offset(LightDiffuse!()) 'diffuse light
    _glLightfv _GL_LIGHT1, _GL_POSITION, _Offset(LightPosition!()) 'light position settings
    _glEnable _GL_LIGHT1 '       enable light

    If Light = -1 Then
        _glDisable _GL_LIGHTING 'disable light
    Else
        _glEnable _GL_LIGHTING
    End If

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

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

        _PutImage (0, _Height(tex&))-(_Width(tex&), 0), tex&, texinv&

        ni& = _CopyImage(texinv&, 32)

        Dim Texture As _Unsigned 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&)

        Dim n As _MEM
        n = _MemImage(ni&)

        Select Case Filter
            Case -1
                'set our texture wrapping
                _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_WRAP_S, _GL_REPEAT
                _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_WRAP_T, _GL_REPEAT
            Case 0
                'set out texture filtering
                _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_MAG_FILTER, _GL_NEAREST 'for scaling up
                _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_MIN_FILTER, _GL_NEAREST 'for scaling down
            Case 1
                _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
            Case 2 'works....not sure, if this output is correct

                'gluBuild2DMipmaps(GL_TEXTURE_2D, pic->bpp/8, pic->width, pic->height, textureType, GL_UNSIGNED_BYTE, pic->data);


                gluBuild2DMipmaps _GL_TEXTURE_2D, 4, _Width(ni&), _Height(ni&), _GL_RGB, _GL_UNSIGNED_BYTE, _Offset(Texture) 'need own memory block (n - MEM) in combination with m - MEM program crash... why?   ? ? ? ? ?
                _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_MAG_FILTER, _GL_LINEAR_MIPMAP_NEAREST 'for scaling up
                _glTexParameteri _GL_TEXTURE_2D, _GL_TEXTURE_MIN_FILTER, _GL_LINEAR '  IF IS USED _GL_LINEAR_MIMAP_NEAREST here, texture is white. Is it correct?    -?-     just God know...
                '


                _glTexImage2D _GL_TEXTURE_2D, 0, _GL_RGB, _Width(ni&), _Height(ni&), 0, _GL_BGRA_EXT, _GL_UNSIGNED_BYTE, n.OFFSET

                _FreeImage tex&
                _MemFree n
                _FreeImage ni&
                GoTo saveit

                'gluBuild2DMipmaps(GL_TEXTURE_2D, 3, TextureImage[0]->sizeX, TextureImage[0]->sizeY, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);

        End Select

        _FreeImage tex&
        _glTexImage2D _GL_TEXTURE_2D, 0, _GL_RGB, _Width(texinv&), _Height(texinv&), 0, _GL_BGRA_EXT, _GL_UNSIGNED_BYTE, m.OFFSET

        saveit:
        U = UBound(GLL)
        GLL(U).PointerGL = Texture
        GLL(U).TextureName = image
        GLL(U).Filtering = Filter
        ReDim _Preserve GLL(U + 1) As GL_Loader

        _MemFree m

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