You can select the AOV type in the AOVs tab of the Arnold Render Setup window. Here you can choose the file type (driver) format which you want to output from MAXtoA.

 

There is a way to view the output image of a render in progress. You must do the following:
  • Set your output to be tiled EXR, zip is fine.
  • Set the bucket scanning method to 'top'.
  • Use a viewer like imf_disp.
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