Any renderer that can render on GPU and CPU can be used to render distributed across a network on GPUs and CPUs. Worst-case situation is that you have to do a few minutes of automation work to move over the scene data, set up a seed and kick off the jobs. Ain't no thing to set up e.g. cycles to render across a bunch of different machines, using the GPU on some, using the CPU on some, using both on some, whatever you feel like.
It doesn't matter how many samples each device in your network gets done, in the end you can always weight them all into one image, and that image will be as if you rendered on a single machine with samples = the sum of all the samples all your machines in the network rendered.
Is it going to be as nice as using tractor? No, but it gets the job done for sure, and it works with any renderer (basically all renderers can be started/controlled by scripts)> Only a few do it, basically the ones you listed, and maybe Maxwell.> We're talking about photorealism here breh
So, what you're saying is... basically every renderer (sans cycles) there is that has a focus on photorealism can do it? I mean, how many more are there? Indigo can also do it, Arion can do it, mental ray can do it, keyshot can do it, and now that's starting to get pretty obscure...
Yeah, renderman can't do it, but that one doesn't focus on realism.