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Extend Horizontal (RGB Curves Node) does not work outside the Clipping boundaries
Open, Confirmed, MediumPublic

Description

Blender Version
Broken: 2.80, 2.79

Short description of error

The Extend Horizontal option of the Compositor's RGB Curves Node
does not work (acts as Extrapolated) outside the boundaries set by the Clipping option.

In the Shader Editor, Extend Horizontal works if the endpoint is in the range [0,1],
but if the endpoint is outside [0,1] it acts as the Extrapolated.

compositor:

shader editor:

Details

Type
Bug

Event Timeline

Philipp Oeser (lichtwerk) triaged this task as Confirmed, Medium priority.

Can confirm for the compositor.
@Jeroen Bakker (jbakker): mind having a look here?

Having trouble reproducing the shader example, seems to work fine here (2.8 rBaf4dcc6073fa)?


@Yevgeny Makarov (jenkm): mind attaching a file (already set up to show the failing in the shader case -- might have done something wrong in my file...)

set the endpoint to 1.25

it looks correctly in the Look Dev:

but Render wrong:


System Information
Operating system: Darwin-18.6.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon Pro 455 OpenGL Engine ATI Technologies Inc. 4.1 ATI-2.9.26

Blender Version
Broken: version: 2.81 (sub 0), branch: master, commit date: 2019-07-30 20:50, hash: rB5359b7a03307

Ah, OK, get it, thx for getting back

Seems to be a dual state problem.

The CRGB curves stores the horizontal extension per curve C, R, G and B. when evaluating the curves only the horizontal extension of the R, G and B channels are checked. The setting in the C-curve is ignored completely. In the files provided the C channel only has the horizontal extension turned on the rest of the channels are turned off hence the extension is not available. I would suggest that this is not a small change, but we needs some overall guidance how this control needs to work. And based on the outcome of this we should make sure all users use the component the same manner.

an option would be to always draw all curves in the control, so the user sees better what happens. Another option would be to only have a single horizontal extension stored that is used by all 4 curves (limits current implementation, but perhaps easier to understand). The second option will break current files.

@Brecht Van Lommel (brecht) how can we move forward with this issue? I checked with Bastien, he proposed to check with you.

Another option would be to only have a single horizontal extension stored that is used by all 4 curves (limits current implementation, but perhaps easier to understand). The second option will break current files.

To me this seems like the right solution, even if it breaks compatibility.