_volumeMappergpu = vtkGPUVolumeRayCastMapper::New();
_volumeMappergpu->AutoAdjustSampleDistancesOn();
volMapperTmp = _volumeMappergpu;
_volumeMappergpu = vtkGPUVolumeRayCastMapper::New();
_volumeMappergpu->AutoAdjustSampleDistancesOn();
volMapperTmp = _volumeMappergpu;