AOVs¶

AOV = Arbitrary Output Variable. An AOV is a render pass that isolates one component of the final image: just diffuse, just specular, just normals, just depth, etc.

Why AOVs¶

Compositors (Nuke, After Effects, Fusion) re-combine AOVs to:

Boost or dim a single component (more specular, less diffuse).
Add light effects only on a specific surface type.
Use depth for depth-of-field in comp.
Re-light a scene without re-rendering.

For standalone skin export, AOVs are usually not needed. For VFX pipelines, they are essential.

The five ship AOVs¶

Rendering > AOV > …:

AOV	Content
Beauty	Final composited image (default; always rendered)
Diffuse	Diffuse-only contribution
Specular	Specular-only contribution
Normal	Per-pixel world-space normal vectors (encoded RGB)
Depth	Per-pixel depth-from-camera (Linear, in scene units)

Beauty is always enabled. The other four are opt-in: tick the checkboxes in the AOV submenu.

Enable AOVs¶

Each AOV's submenu entry toggles it on or off. When at least one non-Beauty AOV is on, the path tracer accumulates additional buffers per ray. Cost scales sublinearly: enabling Normal + Depth adds ~5% to total render time; enabling Diffuse + Specular adds ~15%.

File layout¶

When AOVs are enabled, File > Export > Render produces one EXR multi-channel file plus the Beauty PNG:

out/butterfly_render.png            (Beauty, sRGB PNG)
out/butterfly_render.exr            (multi-channel EXR with all AOVs)

For tools that prefer separate per-AOV files, set Preferences > Rendering > AOV Layout to Per-AOV Files:

out/butterfly_render.beauty.png
out/butterfly_render.diffuse.exr
out/butterfly_render.specular.exr
out/butterfly_render.normal.exr
out/butterfly_render.depth.exr

Custom AOVs (Hypershade route)¶

For non-standard AOVs (e.g. material ID, custom mask), add an AOV Output node in Hypershade:

Drag the AOV Output node into the material graph.
Connect any signal (a Texture, a Math result, a Mask) to its value input.
Set the AOV's name (e.g. "material_id").

The custom AOV appears in the AOV menu and is included in exports.

Depth pass conventions¶

The Depth AOV stores Linear depth in scene units (pixels by default). For compositors that expect normalized 0-1 depth:

Preferences > Rendering > Depth AOV Range: set Min / Max to clip the depth range and normalize.

Limitations¶

Cryptomatte support is roadmap, not v1.
Per-light AOVs (split contributions by light) are roadmap.