I'm using Redshift for a while now and must say its rediculously fast compared to anything I experienced with Mantra. 50 km displaced ocean surface it renders me in a total of 13 seconds, combined with 15 million instanced polygon spheres for whitewater it takes 7 minutes or one full HD frame. In the beginning of the next year we will get direct particle rendering what will raise the particle limits considerably and reduce rendertimes even more.
But as much as people trying to push GPUs a lot of people permit on their CPU workflow. Just a comparison:
https://vimeo.com/195146295 [vimeo.com] this took 7 minutes per frame with 1920*1080 - Redshift
https://vimeo.com/157951443 [vimeo.com] this took 45 minutes per frame with 1280*720 - Mantra
While Mantra is still preparing the displacement of a few km ocean RS is crushing through a lot, lot,lot of frames. With 12 GB of VRAM I already feel quite limitless. With some tricks such as “screen based adaptive” tesselation I can render large scale displacements without any problem at all. Things that would fill up a whole lot more system ram.
I was wondering: what are the tricks to speed up Mantra. A lot of guys are defending it, kind of “you just don't know how” So how?

Some alembic tricks, a bit of packing?