Importance of passes when rendering

Passes

can be used to SPLIT RENDERED IMAGE into colors, direct and indirect light to edit them individually, and also to extract data such as depth or normals. It also allows you to edit individual elements of your image one at a time.

Combined pass

The fully rendered image with all shading, lighting, and compositing applied. Stores the distance of each pixel from the camera in world units. 

Z pass

also known as Depth pass

Mist pass

Stores the distance of each pixel from the camera in world units.

Position pass

Stores the absolute world-space coordinates of each pixel.

Normal pass

Stores surface NORMAL direction data as an RGB image.

Vector pass

Captures motion data of objects and the camera between frames. (also known as Motion Vector)

UV pass

Stores the UV coordinates of surfaces.

Denoising data pass

Stores additional DENOISING information for AI-based denoisers.

Object index pass

Assigns a unique ID value to each OBJECT

Material index pass

Similar to Object Index, but assigns IDs based on MATERIAL

Sample count pass

Stores the number of SAMPLES per pixel used in rendering.

Alpha threshold slider

Controls how alpha transparency is handled in object and Material Index Passes.