Some GPU-accelerated filters have been implemented in ITK. A few simple ones for demonstration purposes and a few others for performance-critical processing.
It is good that you brought up ITK, because the approach we proposed above is essentially the same as ITK’s approach, with the difference that for now we do not plan to use OpenCL but only GLSL (for better compatibility and easier deployment). VTK-m is a really nice effort, but it does more what we need and so it is more complex than we would like, and overall it is an entirely different project. VTK almost does everything that we need, so we prefer to just slightly improve it rather than bring in a completely new framework.
I understand that Kitware does not want to divide its attention between vtk-m and other approaches, but I thought there would be more community members who would want to use GPU for data processing without venturing into vtk-m.