I've checked my issues with slow rendering and yes, setting memory manually fixed issue. Great! -- View this message in context: http://vtk.1045678.n5.nabble.com/VTK-5-6-0-vtkGPUVolumeRayCastMapper-very-slow-tp1249233p5074729.html Sent from the VTK - Users mailing list archive at Nabble.com.