Maniphest T60940

Compositor RGB Curves artefacts with 'film like' option when using individual channels (only works correctly with the 'master' curve)
Confirmed, NormalKNOWN ISSUE
Actions

Assigned To
None
Authored By
Paul R (intracube)
Jan 28 2019, 1:53 AM
Tags
  • BF Blender
  • Compositing
  • User Interface
Subscribers
Alex P (eneen)
Jeroen Bakker (jbakker)
Paul R (intracube)
Philipp Oeser (lichtwerk)
Roman (rwman)

Description

System Information
Operating system: SUSE Leap 15.0
Graphics card: NVidia GTX 560ti (official drivers)

Blender Version
Broken: 2.80, 5632e1b52586, x86_64 linux, 2019-01-24 (buildbot)

Short description of error
Compositor RGB Curves node gives false colours when set to 'Film like' and when any of R,G,B channels are adjusted. Adjustment of C channel alone is OK.

sidenote; Constant hue adjustment is definitely an interesting feature to have! But since film often has various hue shifts going on, if anything, 'Standard' is possibly closer with a typical S-curve - a bias to cyan, magenta, yellow in the highlights corresponding to the curve shoulder.

'Hue hold' or 'Hue lock' could be alternative names.

Example .blend

compositor_rgbcurves_film-like_artefacts.blend111 KBDownload

Exact steps for others to reproduce the error
Load attached .blend, render.

Ref:
https://developer.blender.org/rB4de7c0c3105a80d244dd9f2078c310331873a16b

Notes:

  • Muting the noise texture hides the issue in this example.
  • Stepping through the emission strength from 0.0 to 1.0 gives varying results. Might be a clue to the cause?

Revisions and Commits

rB Blender
Needs ReviewD13387 Fix T60940: Film-like curves produce artefacts

Related Objects

Mentioned Here
rB4de7c0c3105a: Compositor: Film-like curve
rB5632e1b52586: Cleanup: replace VSE /w Sequencer

Event Timeline

Paul R (intracube) created this task.Jan 28 2019, 1:53 AM
Paul R (intracube) added a project: Compositing.
Paul R (intracube) updated the task description.Jan 28 2019, 4:49 AM
Brecht Van Lommel (brecht) assigned this task to Jeroen Bakker (jbakker).Jan 28 2019, 7:58 AM
Brecht Van Lommel (brecht) lowered the priority of this task from 90 to Normal.
Jeroen Bakker (jbakker) added a comment.Feb 22 2019, 3:08 PM
This comment was removed by Jeroen Bakker (jbakker).
Dalai Felinto (dfelinto) removed Jeroen Bakker (jbakker) as the assignee of this task.Dec 23 2019, 4:35 PM
Dalai Felinto (dfelinto) added a project: Tracker Curfew.
Dalai Felinto (dfelinto) added a subscriber: Jeroen Bakker (jbakker).
Philipp Oeser (lichtwerk) added a subscriber: Philipp Oeser (lichtwerk).Feb 7 2020, 1:07 PM

Not knowing the internals well, this really looks "off".
It is especially apparent with soft, gradient like areas, so it breaks quickly with Bloom (like in this case), Glare, Blur and such...

There is a similar example in the comments of rB4de7c0c3105a: Compositor: Film-like curve.
Would have to check the implementations in other software to get a sense if this is "broken by design" or an actual bug in the shuffling of channels or so...

Philipp Oeser (lichtwerk) added a comment.Feb 7 2020, 1:34 PM

Maybe it is also expected to break if done on a particular channel [and not done on the "master" C curve only]?

Paul R (intracube) added a comment.Feb 7 2020, 1:52 PM
In T60940#867434, @Philipp Oeser (lichtwerk) wrote:

Not knowing the internals well, this really looks "off".

Hi, I think it was explained that the film option is only designed to work with adjustments to the 'C' (luminance) channel.

So the simple solution would be to disable the R,G,B channels in that mode.

Philipp Oeser (lichtwerk) claimed this task.Feb 7 2020, 2:53 PM
Philipp Oeser (lichtwerk) edited projects, added User Interface; removed Tracker Curfew.
Philipp Oeser (lichtwerk) changed the subtype of this task from "Report" to "Known Issue".

Also reconfirmed with @Jeroen Bakker (jbakker) that this is only correctly working with the C curve.
So fix is a UI thing: will hide the Film like option when in R G or B curves, and hide R G B when in Film like...

Philipp Oeser (lichtwerk) renamed this task from Compositor RGB Curves artefacts with 'film like' option to Compositor RGB Curves artefacts with 'film like' option when using individual channels (only works correctly with the 'master' curve).Feb 7 2020, 2:54 PM
Julian Eisel (Severin) moved this task from Backlog to Known Issues on the User Interface board.Jun 26 2020, 6:54 PM
Alex P (eneen) added a subscriber: Alex P (eneen).Oct 31 2020, 6:22 PM
Philipp Oeser (lichtwerk) removed Philipp Oeser (lichtwerk) as the assignee of this task.Nov 17 2020, 2:16 PM
Roman (rwman) added a subscriber: Roman (rwman).Jul 21 2021, 1:42 PM
Omar Emara (OmarSquircleArt) added a revision: D13387: Fix T60940: Film-like curves produce artefacts.Nov 27 2021, 12:50 PM
Aaron Carlisle (Blendify) moved this task from Backlog to Known Issues on the Compositing board.Dec 5 2021, 6:58 PM