Is there any way set the render border to be a different shape? I want to render multiple 10000 pixel large image in blender, but the render border only has a rectangular shape (at least from my current knowledge), and it certainly causes unnecessary time because it will render the corner of rectangle render shape. Is there any way to customize thae render border shape?



It would be better if you provide Python solution!Thanks!
The output image will always be rectangular.
But you can mask some parts out using the holdout shader.


Add a mask in front of your camera - it can be a simple plane with a hole
Give it the Holdout shader
In Render Tab check Film > Transparent


Your masked area (and background) will become fully transparent, and will render waaay faster.