Problem summary When combining two bounding boxes using a Merge node with a '0' mix value, the combined bounding box values will not be retain the pixel data generated by the A stream.
If a FilterErode node is added after this Merge operation, the result will also produce a smeared pixel artifact.
Customer reported version nuke.11.2v3
Customer reported platform centos7
Steps to reproduce
Open attached script and view the result.
or
1) Within a new script, create a ColorWheel node
2) Create a Transform node under the ColorWheel node, setting the scale value to 0.5
3) Create a Crop node after the Transform node, isolating the lower quarter of the ColorWheel image
4) Create a Merge node after the Crop node, set this Merge node to an over operation and set the mix value to 0
5) Create another Crop node outside of this node tree, ensuring that the Crop is partially contained within same area as the first Crop
6) View the result of the Merge node and pixel sample (ctrl + drag) over the Colorwheel in the Viewer Result: Pixel values will not exist within the cropped area to the right side of the image, where the second crop was created.
7) Under the Merge node create an Erode(Filter) node and view the results in the Viewer Result: The lack of pixel values are causing a streaming artifact from the above mentioned crop area
Expected behaviour Pixel values should be retained within the merged bounding box and not cause artifacting when using in collaboration with a Filter operation.
Actual behaviour The combination of the bounding boxes create an area with no pixel values and this causes issue downstream with Filter nodes.
Workaround There are several workarounds to this issue:
a) Set the Merge value to 0.001. This will avoid the Merge being a 0 value, which is stopping the pixel values pass through from the A stream with only minimally affecting the image data.
or
b) Break the concatenation in the stream, by adding a node after the Merge operation before the ErodeFilter node. In this situation, the best option would be an AdjustBBox node set to a value of 0 to fill back in the pixel values.
Reproduced by support This bug has been reproduced in: Nuke 11.3v5 - Windows 10 - CentOS 6.9 - MacOS 10.14.5 Nuke 11.3v1 - Windows 10 Nuke 11.2v1 - Windows 10 Nuke 11.1v1 - Windows 10 Nuke 10.5v1 - Windows 10 Nuke 10.0v1 - Windows 10 Nuke 9.0v1 - Windows 10 Nuke 8.0v1 - Windows 10 - CentOS 6.9 - MacOS 10.14.5
Earliest version tested Nuke 8.0v1 - This issue appears to be in all versions of the product
