Where can I find feasible methods for parallelizing rendering?

Hi all,
I have found that when using a personal computer to render a million level grid, there will be lag. I want to optimize it through CPU multiprocessing or simply using GPU, but I can hardly find a method that only uses VTK.
I ran the example in the VTK source code using mpiexec and only got two black windows. I don’t know where the problem is.