[vtkusers] Qt and VTK, vtkTexture and vtkImager

[Carsten Kübler]

Hej vtkdevelopers and users,

during my work to combine qt and vtk (yes I know that there are a few
people who did the same) I noticed several problems with vtk. I wrote a
"new" RenderWindow, RenderWindowInteractor (bases on the version Manish
P. Pagey), ImageWindow, Texture, PolyDataMapper, Imager and an
object-factory for the use of my classes.
And there are a view "bugs" in the vtk 3.1.2 code.

1. vtkOpenGLTexture
#ifdef _WIN32
    ((vtkWin32OpenGLRenderWindow *)
        (ren->GetRenderWindow()))->RegisterTextureResource( this->Index
);
#else
    ((vtkOpenGLRenderWindow *)
        (ren->GetRenderWindow()))->RegisterTextureResource( this->Index
);
#endif

2. vtkOpenGLPolyDataMapper
#ifdef _WIN32
  ((vtkWin32OpenGLRenderWindow *)
        (ren->GetRenderWindow()))->MakeCurrent();
#else
  ((vtkOpenGLRenderWindow *)
        (ren->GetRenderWindow()))->MakeCurrent();
#endif

The two classes ignore other OpenGL implementations like mine and other
vtk/qt implementations.

I propose the redesign of the opengl-implementation of all vtkWindows.
There are 7 classes with "almost" the same gl-code (win32 doesn't clear
the lights during destructing the RenderWindow, win32 uses
VTK_MAX_LIGHTS instead of MAX_LIGHTS, and a lot of other small
differences).

My suggestion.
The vtkWindow has a new aggregated object vtkGraphicExtension. All
OpenGL specific code is in a derived vtkOpenGLGraphicsExtension. All
plattform dependent implementations of vtkWindow use the same
vtkOpenGLGraphicsExtension and use OOP instead of #ifdef !!!! So all
developers of a new vtkOpenGLWindow have not to cut and paste the OpenGL
specific code out of one of seven possible implementations.

Rewrite the 2 classes:
1. vtkOpenGLTexture
    ((vtkOpenGLGraphicsExtension *)
        (ren->GetGraphicExtension()))->RegisterTextureResource(
this->Index );

2. vtkOpenGLPolyDataMapper
   ((vtkOpenGLGraphicsExtension *)
        (ren->GetGraphicExtension()))->MakeCurrent( );

------

Why does a texture register at a vtkRenderWindow but has no possibility
to unregister???

------

The vtkOpenGLImager clears the COLOR_BUFFER_BIT but forgets to clear the
DEPTH_BUFFER_BIT in the Erase() method.

  glClearColor( ((GLclampf)(this->Background[0])),
                ((GLclampf)(this->Background[1])),
                ((GLclampf)(this->Background[2])),
                ((GLclampf)(1.0)) );
  glClear((GLbitfield)GL_COLOR_BUFFER_BIT);

-->

  glClearColor( ((GLclampf)(this->Background[0])),
                ((GLclampf)(this->Background[1])),
                ((GLclampf)(this->Background[2])),
                ((GLclampf)(1.0)) );
  glClearDepth( (GLclampd)( 1.0 ) );
  glClear((GLbitfield)GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

Now the background is painted correctly (in my Qt widget).


Regards
    Carsten Kübler
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