...
It is possible to preview Cooperative jobs while rendering by selecting the job tree and pressing the Preview button. In this moment, the Monitor will ask the Manager for merging the contribution of all the nodes at this instant and display the resulting image in the Preview window as soon as the Manager collects, merges and sends the image to the Monitor.
Merging Manually
If the network fails or crashes at some point and the merging of MXI files is not completed (you can check the Monitor nodes and manager for error messages), you can manually merge the cooperative MXI files created during the render process. All the Render Nodes save the current MXI file in their temp folder (accessible through Menu > Open temp folder). The Manager also stores all the MXI files from the nodes in its temp folder, creating a subfolder for each job so it is easier to find the set of MXI files you are looking for and merge them manually.
In order to make a cooperative render work, each MXI file must have a different starting "seed" so that each render has a slightly different noise pattern. This random seed value is given automatically by the -idcpu command; the user does not have to specify it himself.
...