A little back story…
I recently had to render some 8K and up images in pixel resolution. When I was happy with the framing of my camera I sent the frame off to one of the render nodes to render. Due to our studio setup we don’t have Mental Ray Satellite running, otherwise I may not have noticed the odd behavior of the rendering on my workstation and the studio’s renderfarm blades. When sending a frame to the renderfarm I could see all cores being used, and since they all have 50+ gigs of ram I knew memory wouldn’t be an issue (with other in-house jobs using the farm I moved the rendering to my workstation). Usually I just set my settings to ‘render on local machine’ and “progress messages” as it gives you additional feedback in the output window. These settings are mirrored in my batch render options settings. This time when I hit render it seemed substantially longer for some reason.
There is something set up in the default Mental Ray ‘Current Frame Render’ & ‘Batch Render’ settings that slows the rendering down. I’ve found that when the settings are on default, sometimes both my home & work computers will only use a couple of cores and take up to 4x longer to render. This isn’t always the case though and I can’t replicate the result manually, it just occurs randomly. After looking through the docs and online the only answer I came up with was that many others have run into the same issue.
As my current setup is a bit dated you might need to adjust your threads, tiling size, and memory limit to something that suits your workstation. I’ve just gone through and set mine up by hand since it works really well. With the tick boxes checked Maya takes full control running all of your render settings automatically. I’ve set my Render Threads to the maximum amount – mine is 4 but a lot of new machines are quad or even hexa-core workstations which will have 8 or 12 threads (you will need to count the hyper-threading cores too). I’ve unticked Auto Tiling and changed my pixel width and height to 32, this might be smaller than what Maya determines for your image size but I’ve never had this number fail me over the years. I also set my memory limit by hand; leave a bit for the OS and any other applications that you need to have open. I can’t use Network Rendering so I just untick it – I don’t want Maya running around looking for the Mental Ray Satellite file. You should now notice that all cores are running at close to, if not at 100%. You should also notice that with a smaller task size, larger render sizes are easier to manage. If you’re still unable to render try breaking your scene into tiles from the command line.