This page describes the concept of render passes, essential render elements, and how to use them to create selection masks.
Last updated 29 April 2026
This page describes the concept of render passes, essential render elements, and how to use them to create selection masks.
First, let's define some terms:
Pass – A “once-over” on the rendering to produce a specific effect. You can think of a pass as a “sweep” through the image to do one specific thing.
Render pass – A pass that renders the entire image and stores one or more scene elements, for example, just the lighting or reflections.
Render Element – The results of a render pass that can be combined in a post-process to adjust the final image. It is a regular 2D image, where each pixel has RGB numerical values.
Render Mask – It makes it easy to choose just a part of the image you'd like to rerender. It's more exact and offers more control than Render Region.
Compositing – The combining and adjustment of render elements and/or other elements such as live footage or background plates.
Beauty pass – The combining and editing of certain render elements to create a traditional rendered image.
Multiple Matte Passes
Unshaded solid color images with red, green, and blue colors.
Each color allows control of the selected geometry or materials to which the color has been assigned.
Ambient Occlusion Pass – A shading and rendering technique used to calculate how exposed each point in a scene is to ambient lighting.
Z-Depth Pass – A black-and-white image that shades an object based on the distance from the camera.
The reasoning behind the compositing process is the following: for high-end work such as feature films, rendering straight out of the 3D modeling software/V-Ray may be insufficient to achieve the desired visual quality.
Rendered image might need adjustment to match live-action lighting, color temperature, etc.
The director might want to try different sky backgrounds, combinations of landscape elements, etc.
Common adjustments include color correction, improvement of contrast, adding or enhancing Lens Effects.
Making changes to render elements is faster and easier than re-rendering.
Compositing with render elements provides the solution.
Render elements layered on top of one another to generate the final image.
Render elements can be adjusted individually to produce a specific look.
Compositing of render elements is done in the VFB or outside the 3D modeling app/V-Ray in a compositing program.
Software programs designed for compositing include After Effects, Nuke, Fusion, Photoshop.
Render elements are exported from V-Ray and imported into compositing software.
In compositing, each render element is usually “added” or “multiplied” with previous layers.
In compositing, black = 0 and white = 1
Colored pixel + black pixel = no change
Colored pixel + white pixel = brighter colored pixel (up to pure white pixel)
Colored pixel x black pixel = black pixel
Colored pixel x white pixel = no change
All Render Elements can be exported together in one multi-channel EXR file, or each Render Element can be rendered in its own image file for layering in compositing software. Here, we cover how to achieve these approaches programmatically.
Here's a list of the available render elements which V-Ray provides to the user: