Compositor mix node interpolation bug #49789

New Issue

mickaël bourgeoisat · 2016-10-19T13:32:18+02:00

2016-10-19 13:32:18 +02:00

System Information
windows 10 64 bits
Asus g752 i7 6700HQ gtx 1070
and linux mint 17.3 debian 64 bits
I7 4700 gtx780
Blender Version
2.78 4bb1e22

Short description of error
the mix node interpolation is not correct, it's making sort of filtering.

Exact steps for others to reproduce the error
Take two images as texture image sequences and remove "interpolation" and mip map on them, then add another image with one line black the second white repetively on all the height of the image to use it as mix factor (it can be one line white and another alpha, it's the same result).
You should get one line of the first texture and the second line containing the second texture etc, but that's not the result (please look at the next image).

The purpose of this simple compositing is to recreate fields for TV /sat/TNT diffusion ...
That's a major problem in Blender, because progressive rendering can't be used at all in all the TV industrie, so we have to recreate fields by rendering at 50FPS and mix them correctly with a driver on the offset of each texture image sequence (why is it only possible to remove interpolation on image sequence and only on texture image sequence ?).
As the node compositor is not aware of fields even in blender render, and as cycles doesn't manadge fields at all, we have to do this ugly trick to get back our fields, but that's impossible to do with this bug...
Other consequence, if we use same setup of nodes to create sort of "pixelized" effect for the display on a old TV (for exemple), that can't be done...

Thanks by advance for your interest for this bug.

**System Information** windows 10 64 bits Asus g752 i7 6700HQ gtx 1070 and linux mint 17.3 debian 64 bits I7 4700 gtx780 **Blender Version** 2.78 4bb1e22 **Short description of error** the mix node interpolation is not correct, it's making sort of filtering. **Exact steps for others to reproduce the error** Take two images as texture image sequences and remove "interpolation" and mip map on them, then add another image with one line black the second white repetively on all the height of the image to use it as mix factor (it can be one line white and another alpha, it's the same result). You should get one line of the first texture and the second line containing the second texture etc, but that's not the result (please look at the next image). ![bug.png](https://archive.blender.org/developer/F381303/bug.png) The purpose of this simple compositing is to recreate fields for TV /sat/TNT diffusion ... That's a major problem in Blender, because progressive rendering can't be used at all in all the TV industrie, so we have to recreate fields by rendering at 50FPS and mix them correctly with a driver on the offset of each texture image sequence (why is it only possible to remove interpolation on image sequence and only on texture image sequence ?). As the node compositor is not aware of fields even in blender render, and as cycles doesn't manadge fields at all, we have to do this ugly trick to get back our fields, but that's impossible to do with this bug... Other consequence, if we use same setup of nodes to create sort of "pixelized" effect for the display on a old TV (for exemple), that can't be done... Thanks by advance for your interest for this bug.

mickaël bourgeoisat commented

2016-10-19 13:32:19 +02:00

Changed status to: 'Open'

mickaël bourgeoisat commented

2016-10-19 13:32:19 +02:00

Added subscriber: @myke-octopod

Sergey Sharybin commented

2016-10-21 10:50:14 +02:00

Added subscriber: @Sergey

Sergey Sharybin commented

2016-10-21 10:50:14 +02:00

Please always attach .blend file which demonstrates the issue.

mickaël bourgeoisat commented

2016-10-21 12:39:46 +02:00

Hi Sergey,
Here come the demo file, the problem occur every 24 lines.
Just open entrelacement.blend and hit f12.
demo.zip

Hi Sergey, Here come the demo file, the problem occur every 24 lines. Just open entrelacement.blend and hit f12. [demo.zip](https://archive.blender.org/developer/F383269/demo.zip)

Sergey Sharybin commented

2016-10-21 12:52:07 +02:00

I can't unpack this archive:

End-of-central-directory signature not found.  Either this file is not
a zipfile, or it constitutes one disk of a multi-part archive.  In the
latter case the central directory and zipfile comment will be found on
the last disk(s) of this archive.

Please double-check it is not trunkated or anything like that..

I can't unpack this archive: ``` End-of-central-directory signature not found. Either this file is not a zipfile, or it constitutes one disk of a multi-part archive. In the latter case the central directory and zipfile comment will be found on the last disk(s) of this archive. ``` Please double-check it is not trunkated or anything like that..

mickaël bourgeoisat commented

2016-10-21 15:56:47 +02:00

??? strange, it seems it's the gzification thru the site that modify the archive...
here it come in another format...
down.png.tar.gz
regards
myke

??? strange, it seems it's the gzification thru the site that modify the archive... here it come in another format... [down.png.tar.gz](https://archive.blender.org/developer/F383340/down.png.tar.gz) regards myke

Sergey Sharybin commented

2016-10-21 16:39:20 +02:00

Ok, can see some issues, not sure it is same exact tho. So just to confirm, is your bug about some missing hosizontal stripes (as in, sometimes three blue pixels vertically in a colum)?

Does it also behave correct for you if you replace alpha texture node with an image node?

Ok, can see some issues, not sure it is same exact tho. So just to confirm, is your bug about some missing hosizontal stripes (as in, sometimes three blue pixels vertically in a colum)? ![snapshot47.png](https://archive.blender.org/developer/F383362/snapshot47.png) Does it also behave correct for you if you replace alpha texture node with an image node?

mickaël bourgeoisat commented

2016-10-21 16:50:00 +02:00

Yeap, every 24 lines, you can see a doubled lines, but the "fields" mask is continuous, and we've tried already with image nodes, it's the same problem, plus the image node seems to have a bilenear filtering (interpolation) on it, so it's creating more problems, and we have no more choice than texture image nodes.

Sergey Sharybin self-assigned this 2016-10-21 16:58:27 +02:00

Sergey Sharybin commented

2016-10-21 16:58:27 +02:00

Try adding Pixelate node after the image one, might be a workaround for the time being.

Will have a look into texture nodes..

Try adding Pixelate node after the image one, might be a workaround for the time being. Will have a look into texture nodes..

mickaël bourgeoisat commented

2016-10-21 17:01:00 +02:00

Already tried snifff , still the same :

Already tried snifff , still the same : ![bug2.png](https://archive.blender.org/developer/F383371/bug2.png)

blender-admin commented

2016-10-21 17:56:09 +02:00

This issue was referenced by fd4caafc53

This issue was referenced by fd4caafc53a1c2558f1a27eeaecffb130a146ff4

Sergey Sharybin commented

2016-10-21 17:56:49 +02:00

I meant pixelate hen using image input node to force it to have nearest interpolation.

In any case, think i've got fix for the bug, will be committed in half a minute.

I meant pixelate hen using image input node to force it to have nearest interpolation. In any case, think i've got fix for the bug, will be committed in half a minute.

Sergey Sharybin commented

2016-10-21 17:58:26 +02:00

Forgot to dump another idea, to work around issue in current 2.78 you can try setting x/y offset of texture node to 1e-6 :)

Sergey Sharybin commented

2016-10-21 17:58:49 +02:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2016-10-21 17:58:49 +02:00

mickaël bourgeoisat commented

2016-10-27 01:48:13 +02:00

Hi Sergey, great fix, it's working perfectly well now ;)
I've just tested it in the last 2.78A ;)
Thank you ;)
Have a nice day ;)

Hi Sergey, great fix, it's working perfectly well now ;) I've just tested it in the last 2.78A ;) Thank you ;) Have a nice day ;)

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Compositor mix node interpolation bug #49789