Disjoint Over
A merge operation that layers foreground over background color, but assumes no overlap in partially transparent areas covered by both.
Parameter Types
Parameter descriptions
ForegroundThe
color4foreground input.Frepresents the RGB component of this parameter.frepresents the alpha component of this parameter.BackgroundThe
color4background input.Brepresents the RGB component of this parameter.brepresents the alpha component of this parameter.MixThe weight of the blend operation. The higher the value of
Mix, the more apparent the effect of the blend operation. The default value is1. Values outside of the range0-1produce 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:
[Image]
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:
[Image]