[vtkusers] Transparency

[BERT Sylvain]

Hi Dave, thanks for your answer.
But, indeed, what i want, is the background to be transparent (and not 
the sphere) because i have a video stream behind this sphere.
I have obtained the handle of the vtkwindow (=renWin) by the followng code:
        HWND hwnd = renWin->GetWindowId();
Then, i use this hwnd in a function called MakeAlpha() you can see after.

typedef BOOL (WINAPI *SLWA_FUNC)(HWND hwnd,COLORREF crKey,BYTE 
bAlpha,DWORD dwFlags);

BOOL MakeAlpha(HWND hwnd,BYTE alpha)
{
    // Récupération ddu handle de User32.dll, puis de l'adresse de
    // la fonction SetLayeredWindowAttributes dans cette Dll.
    SLWA_FUNC MySetLayeredWindowAttributes;
    HMODULE hUser32 = GetModuleHandle("USER32.DLL");
    if (!hUser32) return FALSE;
    MySetLayeredWindowAttributes = 
(SLWA_FUNC)GetProcAddress(hUser32,"SetLayeredWindowAttributes");
    if (MySetLayeredWindowAttributes)
    {
        MySetLayeredWindowAttributes(hwnd,0x00FFFFFF,NULL,LWA_COLORKEY);
        //    => toutes les parties blanches seront transparentes
        //       Le reste sera normal
        return TRUE;
    } else {
        // Si pas Windows 2000 ou Windows XP, la fonction 
SetLayeredWindowAttributes
        // n'existe pas, il est donc impossible d'appliquer le paramètre.
        MessageBox(hwnd,"Impossible de passer la fenêtre en 
WS_EX_LAYERED","Erreur",MB_ICONERROR);
        return FALSE;
    }
}
The above function is used by the program but nothing happens. Do i have 
to use an update() function ?


Moreover, i have already used SetOpacity() but it works only on the vtk 
object (sphere) and not on the background.


If you have a idea about this, please let me know.

Thanks a lot.
Sylvain


David.Pont at ForestResearch.co.nz a écrit:

>Hi Sylvian,
>  Do you want to make the sphere transparent, so you will see the
>background through it? Take a look at vtkActor->GetProperty()-SetOpacity.
>Dave Pont
>
>
>|--------+--------------------------------->
>|        |          BERT Sylvain           |
>|        |          <bert at esigetel.fr>     |
>|        |          Sent by:               |
>|        |          vtkusers-admin at public.k|
>|        |          itware.com             |
>|        |                                 |
>|        |                                 |
>|        |          14/02/2003 00:23       |
>|        |          Please respond to bert |
>|        |                                 |
>|--------+--------------------------------->
>  >------------------------------------------------------------------------------------------------------------|
>  |                                                                                                            |
>  |      To:     vtkusers at public.kitware.com                                                                   |
>  |      cc:                                                                                                   |
>  |      Subject:     [vtkusers] Transparency                                                                  |
>  >------------------------------------------------------------------------------------------------------------|
>
>
>
>
>Hi all, i have the following vtk code which is very simple. It's a red
>Sphere on a white background.
>Does anyone know what can i do to have the background transparent ? (The
>transparency works only with W2000 et XP).
>It's very important for me.
>Thanks a  lot !
>
>Sylvain
>
>
>#include "vtkSphereSource.h"
>#include "vtkPolyDataMapper.h"
>#include "vtkActor.h"
>#include "vtkRenderWindow.h"
>#include "vtkRenderer.h"
>#include "vtkRenderWindowInteractor.h"
>#include "vtkWin32OpenGLRenderWindow.h"
>#include "windows.h"
>#include "winuser.h"
>
>
>void main ()
>{
>
>  // create sphere geometry
>  vtkSphereSource *sphere = vtkSphereSource::New();
>  sphere->SetRadius(1.0);
>  sphere->SetThetaResolution(18);
>  sphere->SetPhiResolution(18);
>
>  // map to graphics library
>  vtkPolyDataMapper *map = vtkPolyDataMapper::New();
>  map->SetInput(sphere->GetOutput());
>
>  // actor coordinates geometry, properties, transformation
>  vtkActor *aSphere = vtkActor::New();
>  aSphere->SetMapper(map);
>  aSphere->GetProperty()->SetColor(1,0,0); // sphere color blue
>
>  // a renderer and render window
>  vtkRenderer *ren1 = vtkRenderer::New();
>  vtkRenderWindow *renWin = vtkRenderWindow::New();
>  renWin->AddRenderer(ren1);
>  //renWin->SetFullScreen(true);
>
>  // an interactor
>  vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
>  iren->SetRenderWindow(renWin);
>
>  // add the actor to the scene
>  ren1->AddActor(aSphere);
>  ren1->SetBackground(1,1,1); // Background color white
>
>  // render an image (lights and cameras are created automatically)
>  renWin->Render();
>
>  // begin mouse interaction
>  iren->Start();
>}
>
>
>
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