# Disjoint Over A merge operation that layers foreground over background color, but assumes no overlap in partially transparent areas covered by both. ## Parameter Types |Input |Type | |------------|-------------| |`Foreground`|Color4| |`Background`|Color4| |`Mix` |Float | |Output|Type | |------|-------------| |`Out` |Color4| ## Parameter descriptions - `Foreground`: The `color4` foreground input. `F` represents the RGB component of this parameter. `f` represents the alpha component of this parameter. - `Background`: The `color4` background input. `B` represents the RGB component of this parameter. `b`represents the alpha component of this parameter. - `Mix`: The weight of the blend operation. The higher the value of `Mix`, the more apparent the effect of the blend operation. The default value is `1`. Values outside of the range `0-1` produce an undefined effect outside of the node’s intended function. ## Discussion The Disjoint Over node performs one of two mixes based on the alpha channels of the foreground and background inputs. If `f+b<=1`, then the RGB component of the output is `F+B`. If `f+b>1`, then the RGB component of the output is `F+b(1-f)/b`. The alpha component of the output for this node is always the smaller value between `f+b` or 1. Below is a simple node graph that uses the Disjoint Over node to blend a tile and rock texture:  The graph remaps the alpha of the rock texture from a range of `0-1` to a range of `-1-2` in order to show more of the effect of both possible modes of the blend. Below are the two original images and their resulting blended texture applied to a cube:    --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)