EdgeBlur

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Edge blur blurs edges. But wait! There's more!

Why and how would we want to blur an edge? The edges of things is the point at which a composite succeeds or fails. Sharp edges are unnatural, but so can an edge that is blurred in the wrong way. In a photograph the edges of an object is not blurred in isolation but against the background in which it is located.

In the script below the edges of the foreground shape are blurred before it is merged over the background. Note: The blur was 'powered' by the alpha of the FG. In order for this to happen the FG alpha must be piped through to the merged result. In normal circumstances the alpha of the FG and BG are merged. To get the Merge node to ignore the alpha of the checkerboard the B channel Alpha parameter was unchecked.

In my experience, it is far better to cook your own edge blurs using EdgeDetect and a Blur. This method offers more over control over the result.

Press 'Expand' and select and copy everything below this line, then paste into the Nuke node graph.

set cut_paste_input [stack 0]
version 9.0 v7
StickyNote {
 inputs 0
 name StickyNote1
 label "Here the edge blur is being refering to the \nalpha of the forground (feed 'A')."
 selected true
 xpos -686
 ypos 199
}
CheckerBoard2 {
 inputs 0
 format "1920 1080 0 0 1920 1080 1 HD_1080"
 boxsize 100
 color0 {0.1000000015 0.1000000015 0.1000000015 0}
 color1 {0.5 0.5 0.5 0}
 color2 {0.1000000015 0.1000000015 0.1000000015 0}
 color3 {0.5 0.5 0.5 0}
 centerlinecolor {1 1 0 0}
 name CheckerBoard4
 selected true
 xpos -623
 ypos -34
}
Radial {
 output {-rgba.red -rgba.green -rgba.blue rgba.alpha}
 area {462 160 1218 904}
 softness 0
 color {0.6666666865 1 0.8749980927 1}
 name Radial3
 selected true
 xpos -623
 ypos 46
}
Premult {
 name Premult1
 selected true
 xpos -623
 ypos 78
}
CheckerBoard2 {
 inputs 0
 format "1920 1080 0 0 1920 1080 1 HD_1080"
 name CheckerBoard3
 selected true
 xpos -459
 ypos -28
}
Merge2 {
 inputs 2
 Bchannels {rgba.red rgba.green rgba.blue -rgba.alpha}
 name Merge3
 selected true
 xpos -459
 ypos 78
}
EdgeBlur {
 size 31
 output rgba.alpha
 name EdgeBlur2
 selected true
 xpos -459
 ypos 199
}