The Foundry Nuke's Reformat node issue

Question

I wanted to track my footage and add CG elements to it as part of my nuke project. For that purpose, I undistorted the footage & wrote it down to disk for faster processing. However, when I tried to re-distort the written footage (as shown in attached pic), its not giving me original footage. I found that the Reformat5 and Reformat7 are not giving me the same bounding box dimensions even though both the nodes are the same.

My original footage size is 1920*1080. After undistorting, it becomes 1928*1085.

Hence I put a Reformat4 node with the dimensions 1928*1085 and wrote it down to disk. On the left side, I again put reformat node to resize the undistorted footage back to 1920*1080 with bounding box of size 1928*1085 preserved so as to perform lens distortion to get back my original footage.

Its working fine on left side but if I do the same thing on my written footage, the bounding box dimensions are not same.

Reformat7 gives bounding box of size 1924*1083 instead of 1928*1085. What am I missing here ? I searched the web but I cant find any solution. Please throw some light on this issue.

my nuke script is as follows :

set cut_paste_input [stack 0]
version 10.0 v3
push $cut_paste_input
LensDistortion {
 serializeKnob ""
 serialiseKnob "22 serialization::archive 9 0 0 0 0 0 0 0 0 0 0 0 0"
 distortion1 -0.007498324849
 distortion2 0.0008674863493
 distortionCenter {-0.002916968195 -0.001372990897}
 invertDistortion true
 cardScale {1.006676197 1.006676197 1}
 a 0.001508030226
 b -0.006750627421
 c -0.002457624534
 analysisStart 1
 analysisStop 329
 name LensDistortion2
 selected true
 xpos -451
 ypos 651
}
Reformat {
 format "1928 1085 0 0 1928 1085 1 undistortedFormat2"
 resize none
 name Reformat4
 selected true
 xpos -451
 ypos 684
}
set N6eafc00 [stack 0]
Reformat {
 resize none
 pbb true
 name Reformat5
 selected true
 xpos -451
 ypos 745
}
LensDistortion {
 serializeKnob ""
 serialiseKnob "22 serialization::archive 9 0 0 0 0 0 0 0 0 0 0 0 0"
 distortion1 -0.007498324849
 distortion2 0.0008674863493
 distortionCenter {-0.002916968195 -0.001372990897}
 cardScale {0.9934444427 0.9934444427 1}
 a -0.0004114751064
 b 0.004895505495
 c 0.002436506096
 analysisStart 1
 analysisStop 329
 name LensDistortion3
 selected true
 xpos -451
 ypos 782
}
push $N6eafc00
Write {
 file F:/Assignments/Nuke/CGComp/footages/undistortedFootage1080p/undistortedFootage1080p.####.exr
 file_type exr
 name Write7
 selected true
 xpos -269
 ypos 684
}
Reformat {
 resize none
 pbb true
 name Reformat7
 selected true
 xpos -269
 ypos 747
}
LensDistortion {
 serializeKnob ""
 serialiseKnob "22 serialization::archive 9 0 0 0 0 0 0 0 0 0 0 0 0"
 distortion1 -0.007498324849
 distortion2 0.0008674863493
 distortionCenter {-0.002916968195 -0.001372990897}
 cardScale {0.9934444427 0.9934444427 1}
 a -0.0004114751064
 b 0.004895505495
 c 0.002436506096
 analysisStart 1
 analysisStop 329
 name LensDistortion5
 selected true
 xpos -269
 ypos 783
}

Answer 1

You need to use CopyBBox node for solving your issue. This Python command creates connected CopyBBox node:

import nuke
nuke.createNode("CopyBBox")

or you can create a disconnected one from other nodes with this command:

nuke.nodes.CopyBBox()

CopyBBox copies the bounding box from the A input onto the B stream. The bounding box defines the area of the frame that Nuke sees as having valid image data. The larger the bounding box is, the longer it takes Nuke to process and render the images.

Some NUKE operations, such as a Merge, Blur, or LensDistortion can cause an expansion or decrease of the bounding box area because NUKE does not know that the extra area is going to be black or another constant color. Often, you can fix this by copying the bounding box from one of the inputs to the resulting image, thus cutting off the extra area.

nuke.nodes.Transform(scale=1.005, filter="Mitchell")

And if you have a "Stretched pixels effect" at right margin, use scale=1.005 parameter in Transform node (right after your LensDistortion5 node). Also, don't forget to use filtering algorithm.