VTK Simple question.

[fredscripts]

Hi!

Anyone into VTK (www.vtk.org)? I have this almost-hello world program that shows an sphere:


#include "vtkSphereSource.h"

#include "vtkPolyDataMapper.h"

#include "vtkActor.h"

#include "vtkProperty.h"

#include "vtkRenderWindow.h"

#include "vtkRenderer.h"

#include "vtkRenderWindowInteractor.h"



int main (void)

{



// 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(0,0,1); // sphere color blue



// a renderer and render window

vtkRenderer *ren1 = vtkRenderer::New();

vtkRenderWindow *renWin = vtkRenderWindow::New();

renWin->AddRenderer(ren1);



// 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();

return (1);

}


I would like to add some keyboard response. I mean if I press 'x', that the color of the sphere changes. Using C++.

I cannot find any documentation on google how to do this simple thing. Maybe I'm used to OpenGL and GLUT which has keyboard callbacks and glutPostRedisplay and so and can't figure out here how to do this.


Thanks in advance!

[rCXer]

Wow, a fellow vtk user :guitar: Here's an example. It opens a blank render window and prints the names of the keys pressed in the console. Btw, a good place to get help are the vtk mailing lists (http://www.vtk.org/cgi-bin/mailman/listinfo).


#include <iostream>
#include "vtkCommand.h"
#include "vtkRenderer.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkRenderWindow.h"
#include "vtkCallbackCommand.h"

using namespace std;

//Calback functions take this form. I have no idea why :(.
void keypressFunction(vtkObject* caller, unsigned long event, void* clientdata, void* calldata)
{
/*The object that called this function should be the render window interactor.
Therefore create an render window interactor and cast it as the caller. */
vtkRenderWindowInteractor *iren = (vtkRenderWindowInteractor*)caller;

//Stuff to do when key is pressed. In this case just print the keys symbol.
cout<< iren->GetKeySym() <<endl;
}

int main(void)
{
vtkRenderWindow *renWin = vtkRenderWindow::New(); //Creat renWin.
vtkRenderer *ren = vtkRenderer::New(); //Create renderer...
renWin->AddRenderer(ren); //...and assign it to renWin.

vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New(); //Create interactor...
renWin->SetInteractor(iren); //...and asign it to renWin.

vtkCallbackCommand* keypressCommand = vtkCallbackCommand::New(); //Create keypressCommand...
keypressCommand->SetCallback(keypressFunction); //...and tell it to go to keypressFunction ...
iren->AddObserver("KeyPressEvent", keypressCommand); //...when a "KeyPressEvent" occurs in iren.

//Put more stuff here
renWin->Render(); //Render your stuff
iren->Start(); //Start the interactor

return 0;
}

Here's my CMakeLists.txt (in case you are using cmake). It includes more libraries than you'll ever need.


PROJECT(Keypress)

FIND_Package(VTK)
IF(VTK_FOUND)
INCLUDE(${VTK_USE_FILE})
ELSE(VTK_FOUND)
MESSAGE(FATAL_ERROR "VTK not found. Please set VTK_DIR.")
ENDIF(VTK_FOUND)

ADD_EXECUTABLE(Keypress Keypress.cpp)
TARGET_LINK_LIBRARIES(Keypress vtkCommon vtkRendering vtkGraphics vtkHybrid vtkImaging vtkIO vtkFiltering vtkCommon)

[fredscripts]

Thanks so much. If instead of printing key symbol I wanted to change the background color/do whatever with the elements of the window, do you know how could I do it? Something like /* do sth */ and renWin->Update()?

[rCXer]

Replace...


cout<< iren->GetKeySym() <<endl;

...with...


vtkRenderWindow *renWin = iren->GetRenderWindow(); //Get the render window from our interactor.
vtkRendererCollection *rens = renWin->GetRenderers(); //Get the a list of renderers in our render window
vtkRenderer *ren = rens->GetFirstRenderer(); //Get the first renderer from list. Since we only have 1 renderer this is the one we want.
ren->SetBackground(0,1,1); //Set background to cyan.
renWin->Render(); //Render our stuff.

... and make sure you include...


#include "vtkRendererCollection.h"

...to the beginning of your file.

All this does is change the background to cyan when a key is pressed. If you want to work with the actor (the sphere in your case) just get the actor collection from the renderer and then get the first actor.