Region--
The 3D process is one of constant iteration and refinement. Rendering entire images repeatedly is a significant waste of time and a disruption to the creative workflow. To alleviate some of this pain modo provides the 'Render Region' rendering functionality. Users may use the Left/Right/Top/Bottom functions to specify the region manually, or use the 'Render Region Tool' to specify an area by dragging in any 3D viewport. Additionally, the function can be activated through a button of the 'Render Display' window, under the options tab. When enabled, the next time a render command is invoked (such as by pressing 'F9'), only the area within the region specified will be rendered. The function can be disabled by toggling the 'Render Region' setting.
Limited Region
Render Region: This button toggles the 'Render Region' function on and off.
Left/Right/Top/Bottom: Left/Right and Top/Bottom percentage settings work in conjunction with each other to specify the total rendered region width and height. One could easily render the left half of the image, regardless of the output resolution or aspect ratio, by setting the 'Right' value to 50%. One can also easily set a specific area by click dragging over the rendered image in the Render Preview Window. When you do that, the render region toggle is automatically activated. Outside of disabling the function with the 'Render Region' toggle, a single click anywhere on the 'Render Display' window will restore the render to the full frame.