A solution to render large scale images for print in maya without using any code.
There are 2 distinct ways I have found to do this. The first, and seemingly unreliable way, is using the command line to render out tiles of the viewport then stitch them together in photoshop (Instructions here). I am no programmer and could not get this to work, you may have already found and tried it, but if it has failed for you too then this should provide a slightly more intuitive way!
The Instructions.
I found it easier to divide my image into strips rather than a grid. So, I set the camera (image size in the rendering options) to the width of the scene and 1/10th the hight. Next I changed the film translation in the camera options so that the viewport lined up with the top of the scene and rendered. Changing the film translation rather than where the camera was pointing allowed me to aim the viewport without changing the perspective or angle. From here I moved the viewport down for each render and stitched them all together in photoshop.
That's it! Sweet and simple.
Some tips.
Before rendering I saved out a snapshot of the wireframe to aid in the alignment in photoshop.
The height of my renders were just over 1/10th so as to avoid any gaps between the strips.
If you are using final gathering, render out the final gather map then freeze it to avoid artefacts at the seams. Personally I could' work this out so i used the overlap between strips as a fade and therefor minimised the visibility of seams.
I created a grid as an image, placed it onto a plane and lined it up with the camera before changing any of the settings to render, this made the job of lining up the viewport much easier as it was mainly guessing. I had no calculations to line up the viewport exactly.
How I figured this out.
My idea started very simply. I made a grid over the scene and pointed the camera at each tile in turn to render them. These renders would then be stitched in photoshop as the final, full res image. The problem is the shift in perspective and angle. To sort this I had a poke around in the camera settings and found the film translate options. If you have come across tilt shift photography you should understand the concept behind this, if you have not - look it up, it will blow your mind! I also figured at this point I didn't need to render a grid, just a set of strips - they' be much easier to line up and as it turns out my computer had a much larger capacity to render big than I thought. The result of this is 10 strips to line up in one axis rather than 100 to line up in two, I reckon this made the job around 20 times as easy. So I changed the translation, rendered the top strip, then carried on down the scene.