Rendering 9.6 million tetrahedrons for visualization of a volumetric domain in 3D using python

I am writing a code to render the surface of an entire human body’s mesh. There are nearly 9.6 million tetrahedrons on the surface of this mesh. Even though the code is parallelized to run, it takes a huge amount of time (weeks) and doesn’t render anything. I know the code works cos I have tried to render smaller domains which works smoothly. The only function that is consuming the most time is addActor().
Could someone help me in understanding a better way to avoid addActor() or is there a limit of mesh elements that can be rendered using VTK?

9.6 million cells is not a lot. Rendering should be very fast, without any parallelization in your code.

How many actors did you use for the rendering? What did you parallelize?
What CPU and graphics chipset and how much RAM do you have?