[vtkusers] Using ExternalVTKWidget with an external OpenGL context (OpenSG)

[Christian Bar]

Dear All,
I am trying to draw some VTK stuff inside a pre-existing OpenGL context;
this context has been created with a library called OpenSG (not to be
confused with OpenSceneGraph).

After some trial-and-error development, I managed to adapt a OpenSG example
and integrate some VTK rendering. In the initialization phase I:
- create an OpenSG GLUT window and put a torus inside the OpenSG scene,
- create a VTK ExternalVTKWidget and related window/renderer, and put a
cube inside the VTK scene.
In the GLUT main loop, I:
- activate the OpenSG window,
- draw the OpenSG torus,
- setup some GL stuff for camera and lights (why?!?),
- draw the VTK cube,
- swap buffers and deactivate the OpenSG window.

Now, my questions are essentially two:
1) Why do I need to write the OpenGL/glu code for the camera and the
lights? It seems to me that OpenSG correctly calls the OpenGL state machine
and sets up the camera and lights, but, when it comes to VTK, the internal
camera and lights settings are not used (for example, if I set the camera
near and far plane in the vtkRenderer it is ignored, to get everything work
I have to call the gluPerspective() on each frame). The same for the
Modelview tranform.
2) When I quit the application, a VTK window opens and prompts me for some
OpenGL errors: "
Generic Warning: In
..\..\..\VTK-6.3.0\Rendering\OpenGL\vtkOpenGLDisplayListPainter.cxx, line 52
failed after ReleaseAllLists 16 OpenGL errors detected
  0 : (1282) Invalid operation
  1 : (1282) Invalid operation
  2 : (1282) Invalid operation
  3 : (1282) Invalid operation
  4 : (1282) Invalid operation
  5 : (1282) Invalid operation
  6 : (1282) Invalid operation
  7 : (1282) Invalid operation
  8 : (1282) Invalid operation
  9 : (1282) Invalid operation
  10 : (1282) Invalid operation
  11 : (1282) Invalid operation
  12 : (1282) Invalid operation
  13 : (1282) Invalid operation
  14 : (1282) Invalid operation
  15 : (1282) Invalid operation
", can someone tell me why?

Currently , I am developing with Visual Studio 2010.
Any suggestion or hint will be highly appreciated!
Kind Regards,
Christian

PS: below you can find the complete example:

#include <vtkAutoInit.h>
VTK_MODULE_INIT(vtkRenderingOpenGL);
VTK_MODULE_INIT(vtkRenderingContextOpenGL);
VTK_MODULE_INIT(vtkRenderingFreeType);
VTK_MODULE_INIT(vtkInteractionStyle);

// OSG Includes
#include <OSGGLUT.h>
#include <OSGConfig.h>
#include <OSGSimpleGeometry.h>
#include <OSGGLUTWindow.h>
#include <OSGSimpleSceneManager.h>
#include <OSGPerspectiveCamera.h>

// VTK includes
#include <ExternalVTKWidget.h>
#include <vtkActor.h>
#include <vtkCallbackCommand.h>
#include <vtkCamera.h>
#include <vtkCubeSource.h>
#include <vtkExternalOpenGLRenderWindow.h>
#include <vtkNew.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>

// defines
#define FOV 75.f
#define NEAR_PLANE 0.01f
#define FAR_PLANE 100.0f

// variables
vtkNew<ExternalVTKWidget> externalVTKWidget;
vtkNew<vtkActor> actor;
int width = 100, height = 100;
OSG::SimpleSceneManagerRefPtr mgr;
OSG::GLUTWindowRefPtr gwin;

using namespace OSG;

// redraw the window
void display(void)
{
// activate OSG window
gwin->activate();
gwin->frameInit();

// draw OSG stuff
mgr->update();
gwin->renderAllViewports(mgr->getRenderAction());

// setup gl stuff for camera and lights (why?!?)
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective (FOV, (float)width/(float)height, NEAR_PLANE, FAR_PLANE);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);

// draw VTK stuff
actor->RotateX(1.0f);
actor->RotateY(1.0f);
externalVTKWidget->GetRenderWindow()->Render();

// swap buffers and deactivate OSG window
gwin->swap();
gwin->frameExit();
gwin->deactivate();
}

// react to size changes
void reshape(int w, int h)
{
width = w;
height = h;
mgr->resize(w, h);
glutPostRedisplay();
}

// react to mouse button presses
void mouse(int button, int state, int x, int y)
{
if (state)
mgr->mouseButtonRelease(button, x, y);
else
mgr->mouseButtonPress(button, x, y);
glutPostRedisplay();
}

// react to mouse motions with pressed buttons
void motion(int x, int y)
{
mgr->mouseMove(x, y);
glutPostRedisplay();
}

// react to keys
void keyboard(unsigned char k, int x, int y)
{
switch(k)
{
case 27:
{
mgr = NULL;
gwin = NULL;
OSG::osgExit();
exit(0);
}
break;
}
}


int main(int argc, char **argv)
{
// init and setup GLUT
glewInit();
OSG::osgInit(argc,argv);
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
int winid = glutCreateWindow("OpenSG");
glutReshapeFunc(reshape);
glutDisplayFunc(display);
glutIdleFunc(display);
glutMouseFunc(mouse);
glutMotionFunc(motion);
glutKeyboardFunc(keyboard);

{
// Connection between GLUT and OpenSG
gwin = OSG::GLUTWindow::create();
gwin->setGlutId(winid);
gwin->setSize(100, 100);
gwin->init();

// create the scene
OSG::NodeRefPtr scene = OSG::makeTorus(.1f, 0.6f, 16, 16);
OSG::commitChanges();
mgr = OSG::SimpleSceneManager::create();
mgr->setWindow(gwin );
mgr->setRoot  (scene);
mgr->showAll();

// set the camera parameters
CameraRecPtr cam = mgr->getCamera();
PerspectiveCamera *pPerspCam =
OSG::dynamic_pointer_cast<PerspectiveCamera>(cam);
pPerspCam->setFov(FOV);
pPerspCam->setNear(NEAR_PLANE);
pPerspCam->setFar(FAR_PLANE);
pPerspCam->setAspect(1.f);
}

{
// create the VTK scene
vtkNew<vtkCubeSource> cs;
vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputConnection(cs->GetOutputPort());

actor->SetMapper(mapper.GetPointer());
actor->GetProperty()->SetColor(1,1,0.2);
actor->GetProperty()->SetOpacity(0.5);

// create the VTK external renderer
vtkNew<vtkExternalOpenGLRenderWindow> renWin;
externalVTKWidget->SetRenderWindow(renWin.GetPointer());
vtkRenderer* ren = externalVTKWidget->AddRenderer();
ren->AddActor(actor.GetPointer());
}

glutMainLoop();
return 0;
}
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