appleseed Users Forum

About AOVs

Maybe this question is too simple, but I want to get more information about AOV.

I learned some about AOV, they refer to render passes, right? and AOV is abbreviation of ‘’Arbitrary Output Variable"?[https://forums.cgsociety.org/t/what-the-heck-are-aovs/1735757]

As I know, using AOV means using multiple render passes for each channel,
image

for example, one pass for “albedo”, one pass for “diffuse” and so on.

If this is right, then what the advantages and disadvantages of this technique? I guess AOV can get better result, but cost more time for rendering. If so, Why AOV can get better result?

following is your aov test scene

and i can see you can get different layer image:

diffuse:
image

glossy:
image

How to get these images? I opened Diagnostics menu and can not find it:
image

and @Mongo3 mentioned in [First couple of tests for review] that using AOV can distinguish different contributions

Yes, indeed. The name Arbitrary Output Variable is not very informative but now considered industry wide adopted. What it refers to are additional outputs of the render engine mainly used for compositing. These outputs can contain for instance parts of the lighting (direct or indirect or caustics contributions, emission, transmission or reflection and many others e.g. shading, denoiser and sampling related ones)

The advantages are that one can individually tweak them in compositing (when they can be added up to give the final beauty render output) which allows for great flexibility. For instance one could just denoise selectively the indirect-diffuse pass if this one has the largest noise contributions or by using the albedo pass denoise only the lighting while keeping the texture detail intact.

The drawback is extra memory and disk space is required as well as extra setup work. Some engines allow for individual camera and render settings for each render layer overriding the global settings.

In appleseed we have also Diagnostic Shading Overrides which can be accessed with the menu you showed in appleseed.studio (AOVs cannot yet be accessed in studio)
Shading overrides serve a similar purpose as AOVs but are not intended for compositing. They give diagnostic information about the scene, shader and objects and are used to check the scene.

A list of supported shading overrides:

Thanks for the detailed information. So How can I render different layer image? for example the “glossy aov” layer as the above image shows. The “Diagnostic Shading Overrides” does not have glossy. How do you get the following image
image

As I wrote above, in appleseed.studio output and display of AOVs is unfortunately not yet implemented. It is a long standing feature request https://github.com/appleseedhq/appleseed/issues/269

If you use one of our plugins you can select the AOVs in a menu and with blenderseed even preview them in the render-view. With appleseed-Max & appleseed-Maya they are saved as .EXR files on disk.

Screenshot shows the AOV selection menu in blenderseed for Blender 2.8

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Ok Got it