Grease pencil eyedropper doesn't sample correct vertex color. #82992

New Issue

Jonathan Mielke · 2020-11-25T11:15:03+01:00

Jonathan Mielke commented

2020-11-25 11:15:03 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 457.30

Blender Version
Broken:

version: 2.90.0, branch: master, commit date: 2020-08-31 11:26, hash: `rB0330d1af29c0`
version: 2.92.0 Alpha, branch: master, commit date: 2020-11-24 16:32, hash: `rBe922dd7d8a30`
version: 2.83.9, branch: master, commit date: 2020-11-11 06:30, hash: `rB4abfc0bcd5c8`

Worked: (unknown maybe never)

Short description of error
When using the grease pencil eye dropper with filmic color management selected; the sampled color is different than the original vertex stroke color.
Works as expected with standard color management selected
(Note this is confusing to new users as they expect to color sample and return the previous color of their previous stroke.)

with filmic enabled:	with filmic disabled:

Exact steps for others to reproduce the error

Start with a new file
Set color management to filmic.
Add grease pencil object
Enter Draw Mode
Paint in vertex color mode using a lighter color.
With a blank palette use the color eyedropper tool on the stroke you just made
now paint with the sampled color in the palette
result should be slightly darker than the first stroke.

video reference:
with filmic enabled:
Desktop 2020.11.25 - 02.35.06.03.mp4

with filmic disabled:
Desktop 2020.11.25 - 02.36.30.06.mp4

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 457.30 **Blender Version** Broken: ``` version: 2.90.0, branch: master, commit date: 2020-08-31 11:26, hash: `rB0330d1af29c0` version: 2.92.0 Alpha, branch: master, commit date: 2020-11-24 16:32, hash: `rBe922dd7d8a30` version: 2.83.9, branch: master, commit date: 2020-11-11 06:30, hash: `rB4abfc0bcd5c8` ``` Worked: (unknown maybe never) **Short description of error** When using the grease pencil eye dropper with filmic color management selected; the sampled color is different than the original vertex stroke color. Works as expected with standard color management selected (Note this is confusing to new users as they expect to color sample and return the previous color of their previous stroke.) |with filmic enabled:|with filmic disabled:| |--|--| |<video src="https://archive.blender.org/developer/F9371464/Desktop_2020.11.25_-_02.35.06.03.mp4" controls></video>|<video src="https://archive.blender.org/developer/F9371475/Desktop_2020.11.25_-_02.36.30.06.mp4" controls></video>| **Exact steps for others to reproduce the error** - Start with a new file - Set color management to filmic. - Add grease pencil object - Enter Draw Mode - Paint in vertex color mode using a lighter color. - With a blank palette use the color eyedropper tool on the stroke you just made - now paint with the sampled color in the palette - result should be slightly darker than the first stroke. video reference: **with filmic enabled:** [Desktop 2020.11.25 - 02.35.06.03.mp4](https://archive.blender.org/developer/F9371464/Desktop_2020.11.25_-_02.35.06.03.mp4) **with filmic disabled:** [Desktop 2020.11.25 - 02.36.30.06.mp4](https://archive.blender.org/developer/F9371475/Desktop_2020.11.25_-_02.36.30.06.mp4)

Jonathan Mielke commented

2020-11-25 11:15:03 +01:00

Added subscriber: @JSM

blender-admin commented

2020-11-25 11:15:03 +01:00

#83129 was marked as duplicate of this issue

Philipp Oeser commented

2020-11-25 12:39:14 +01:00

Added subscribers: @antoniov, @Jeroen-Bakker, @lichtwerk

Philipp Oeser commented

2020-11-25 12:39:14 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Philipp Oeser commented

2020-11-25 12:39:14 +01:00

Yep, Grease Pencil "just" uses eyedropper_color_sample_fl which can pick up colors from Image Editors, Compositor etc. correctly, but "only" uses simple OpenGL pixel reading in the 3D viewport.
So in fact, the above actually goes through colormanagement (eyedropper_color_sample_fl does IMB_colormanagement_display_to_scene_linear_v3 & eyedropper_gpencil_color_set does IMB_colormanagement_scene_linear_to_display_v3), but you get possible viewport shading happening to strokes baked in and also exposure and gamma [@Jeroen-Bakker: not sure if these are part of the OCIO processing?]

It would be good indeed to be similar to texture painting, where paint_sample_color goes in and does not sample the viewport pixel but the texture color [at least if the Sample Merged option is OFF].
So for Grease Pencil, this would need to add the Sample Merged option, pick up the color from the material [and/or Vertex Color] and not using OpenGL [OpenGL should only be used if Sample Merged option is ON].

This is not a bug though (more of a TODO), it is just not implemented that way, would like to ask @antoniov and @Jeroen-Bakker though if they would like to keep this task open (it is definitely useful to pick "correct" colors from other strokes as well, no?)
Will confirm for now.

Yep, Grease Pencil "just" uses `eyedropper_color_sample_fl` which can pick up colors from Image Editors, Compositor etc. correctly, but "only" uses simple OpenGL pixel reading in the 3D viewport. So in fact, the above actually goes through colormanagement (`eyedropper_color_sample_fl` does `IMB_colormanagement_display_to_scene_linear_v3` & `eyedropper_gpencil_color_set` does `IMB_colormanagement_scene_linear_to_display_v3`), but you get possible viewport shading happening to strokes baked in and also exposure and gamma [@Jeroen-Bakker: not sure if these are part of the OCIO processing?] It would be good indeed to be similar to texture painting, where `paint_sample_color` goes in and does not sample the viewport pixel but the texture color [at least if the `Sample Merged` option is OFF]. So for Grease Pencil, this would need to add the `Sample Merged` option, pick up the color from the material [and/or Vertex Color] and not using OpenGL [OpenGL should only be used if `Sample Merged` option is ON]. This is not a bug though (more of a TODO), it is just not implemented that way, would like to ask @antoniov and @Jeroen-Bakker though if they would like to keep this task open (it is definitely useful to pick "correct" colors from other strokes as well, no?) Will confirm for now.

Antonio Vazquez commented

2020-11-25 12:46:59 +01:00

You are right @lichtwerk, the difference is the color correction and if there is a way to skip this, maybe it would be better.

Anyway, also can be differences if you sample a stroke in a grease pencil with the lighting enabled, because the color can change.

We can keep this open as ToDo.

You are right @lichtwerk, the difference is the color correction and if there is a way to skip this, maybe it would be better. Anyway, also can be differences if you sample a stroke in a grease pencil with the lighting enabled, because the color can change. We can keep this open as ToDo.

Robert Guetzkow commented

2020-11-27 23:05:45 +01:00

Added subscriber: @Jkecwlkr

Philipp Oeser removed the

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Grease pencil eyedropper doesn't sample correct vertex color. #82992