VFX I

6.1 Arnold AOVs


Arnold

For Arnold, the render passes setup is pretty straight foreward

Material properties equal render passes

Lighting can be split in direct and indirect


Possible AOV combinations

Beauty = direct + indirect + emission

Beauty = diffuse + specular + transmission + sss + coat + emission

Beauty = (diffuse_direct + specular_direct + transmission_direct + sss_direct + coat_direct) + (diffuse_indirect + specular_indirect + transmission_indirect + sss_indirect + coat_indirect) + emission



Arnold aiStandard Surface

Base = diffuse pass
Specular = specular pass
Transmission = transmission pass
Subsurface = sss pass
Coat = coat pass
Emission = emission pass

AOV Setup
  1. Select passes from the Available AOVs
  2. Add to Active AOVs column

If your materials have Weight in diffuse, specular, transmission, subsurface, coat, emission – add the corresponding pass

Always include the RGBA beauty

For even more control, add direct and indirect for each pass


Multi-Channel EXR or Separate Files

The OpenEXR file format supports multi-channel, means all render passes can go into one EXR file per frame. The channels can then be accessed in Nuke individually

Separate Files mean each pass is rendered into an individual file per frame, making it more obvious which passes have been rendered

Both methods have their pros and cons. Multi-Channel EXR are cleaner but if only a fraction of the embedded channels are used, the entire file still has to pass through the network

 

Default Folder and File Names

For Multi-Channel EXR, all passes are simply merged into one larger file

For separate files, Maya 2017 creates folders for each pass

Not very useful: All files have the same name. Let’s change that


Recommended Naming

In Render Settings > Common > Right-click in File name prefix field

Add tags seperated by / slash to define folders. Last element is file name

With more than one render layer, you want the <RenderLayer> tag in the filename

Multi Channel EXR: <Scene>/<RenderLayer>/<Scene>_<RenderLayer>

Seperate Files: <Scene>/<RenderLayer>/<Scene>_<RenderLayer>_<RenderPass>


v – versions

Using the v for incremental versions of a filename is highly recommended in general

One key-stroke (ALT + arrow up) to update Nuke Read nodes to next version, if the folder and filename use v+digit



Enable Multi-Channel EXR

If you prefer combining all passes into one EXR

Render Settings > AOVs > Select Driver on any pass to access default driver


Merge AOVs

To enable, tick MergeAOVs

This will merge all passes, not only the selected one


Disable AOVs for Specific Layer

The Shadow render layer from the previous IBL example does not need AOVs, only the FG layer

To disable AOVs for a specific Layer

Render Settings > Select Render Layer

AOVs > right-click on Mode and
Create Absolute Override for Visible Layer


aovMode Override

Render Setup > select the Override

In the Property Editor, change AoV Mode to disable



More info: Arnold 5 for Maya user guide