Lighting & rendering · Intermediate

Render passes

Separate images of a render’s lighting, shadows, depth and masks

Also called AOVs, arbitrary output variables

What are render passes?

Render passes are separate images a renderer saves alongside the final frame, each holding one ingredient of it, such as diffuse color, reflections, shadows, depth or object masks. Also called AOVs, they let you adjust each part in compositing without rendering the whole scene again.

Think of it like this

It is like a recording studio keeping vocals, drums and guitar on separate tracks, so you can turn one up later without recording the band again.

Where it fits in a 3D project

  1. Create
  2. Surface
  3. Rig
  4. Animate
  5. Render
  6. Export

Render: Lighting the scene and turning it into images or video.

How render passes work

  1. 01You choose which passes to save in the render settings.
  2. 02The renderer writes each pass as its own image or layer while rendering.
  3. 03In compositing, the passes are combined back into the final picture.
  4. 04Changing one pass, such as reflections, adjusts that part alone.

Render passes vs render layers

PropertyRender passesRender layers
Splits byType of light and dataObjects or groups in the scene
ExampleShadows, reflections, depthCharacters, background, props
Main useTweaking lighting after the renderRendering parts of a scene separately

Use render layers to separate what is in the scene and render passes to separate how it is lit. Most compositing setups use both.

Where render passes are used

  • Fixing reflections or shadows without a re-render
  • Adding depth of field or fog in compositing
  • Masks for color grading single objects

Beginner tip

Save to a multilayer image format so every pass travels in one file. Turn on only the passes you will use, because each one adds disk space and memory.

Terms related to render passes

Render passes FAQ

What are AOVs in rendering?
AOV stands for arbitrary output variable, another name for a render pass. Some apps also use it for custom passes you define yourself, such as one material’s color.
Why use render passes for compositing?
They make changes cheap. Instead of re-rendering for a brighter reflection or a softer shadow, you adjust that pass in seconds. They also supply masks and depth for effects added later.
Do render passes slow down rendering?
Slightly. The heavy lighting work is done either way, so extra passes mostly cost memory and file size. Many passes at high resolution can still add up.

Updated October 29, 2026 · Browse all 3D terms