add: case 'a': { OSG::beginEditCP(vol, OSG::DVRVolume::SamplingFieldMask); vol->setSampling(vol->getSampling() * 1.1); OSG::endEditCP(vol, OSG::DVRVolume::SamplingFieldMask); std::cout << "Sampling set to " << vol->getSampling() << std::endl; glutPostRedisplay(); } break; case 'z': { OSG::beginEditCP(vol, OSG::DVRVolume::SamplingFieldMask); vol->setSampling(vol->getSampling() * 0.9); OSG::endEditCP(vol, OSG::DVRVolume::SamplingFieldMask); std::cout << "Sampling set to " << vol->getSampling() << std::endl; glutPostRedisplay(); } break;
context: void keyboard(unsigned char k, int OSG_CHECK_ARG(x), int OSG_CHECK_ARG(y)){    switch(k)    {        case 27:                {            OSG::osgExit();            exit(0);        }        break;    }}