RGB Curves node having an effect on components that they shouldn't. #48685

New Issue

George Muhs · 2016-06-19T23:28:48+02:00

George Muhs commented

2016-06-19 23:28:48 +02:00

System Information
Ubuntu 14.04 and graphics card Intel HD 4600 Graphics

Blender Version
Broken: (example: 2.77a abf6f08

Short description of error
The bug deals with the RGB Curves suppressing the lens flare AFTER the Alpha Over node.
The concept in the node tree is to color correct the ship object which is off screen at this time. Based on the RGB Curves location in the node tree the expectation is that the color correction would be limited to the ship object. However if you un-mute the RGB Curves node You will see that it also gets applied to the image coming in from the Add node. I have observed this behaviour also in the Brightness/Contrast node. That however does not seem to show up in this composite tree if I put the Brightness/Contrast node in the tree in place of the RGB Curves.

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

Blend File: bug_rgb-curves_brightness-contrast_01.blend

**System Information** Ubuntu 14.04 and graphics card Intel HD 4600 Graphics **Blender Version** Broken: (example: 2.77a abf6f08 **Short description of error** The bug deals with the RGB Curves suppressing the lens flare AFTER the Alpha Over node. The concept in the node tree is to color correct the ship object which is off screen at this time. Based on the RGB Curves location in the node tree the expectation is that the color correction would be limited to the ship object. However if you un-mute the RGB Curves node You will see that it also gets applied to the image coming in from the Add node. I have observed this behaviour also in the Brightness/Contrast node. That however does not seem to show up in this composite tree if I put the Brightness/Contrast node in the tree in place of the RGB Curves. **Exact steps for others to reproduce the error** Based on a (as simple as possible) attached .blend file with minimum amount of steps Blend File: [bug_rgb-curves_brightness-contrast_01.blend](https://archive.blender.org/developer/F317730/bug_rgb-curves_brightness-contrast_01.blend)

George Muhs commented

2016-06-19 23:28:48 +02:00

Changed status to: 'Open'

George Muhs commented

2016-06-19 23:28:48 +02:00

Added subscriber: @GeorgeMuhs

Sergey Sharybin commented

2016-06-28 11:48:52 +02:00

Added subscriber: @Sergey

Sergey Sharybin commented

2016-06-28 11:48:52 +02:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2016-06-28 11:48:52 +02:00

Sergey Sharybin self-assigned this 2016-06-28 11:48:52 +02:00

Sergey Sharybin commented

2016-06-28 11:48:52 +02:00

With this particular file the difference is caused by RGB curves pushing colors to negative region. After alpha-overing negative colors on top of something some areas might become darker, or even bigger artifacts might appear because of alpha-over result also going negative colors.

So far i don't really see failure of Blender here.

If you've got issues with cases when there are no negative colors involved, please upload new .blend file with all included data needed to reproduce that exact issue.

With this particular file the difference is caused by RGB curves pushing colors to negative region. After alpha-overing negative colors on top of something some areas might become darker, or even bigger artifacts might appear because of alpha-over result also going negative colors. So far i don't really see failure of Blender here. If you've got issues with cases when there are no negative colors involved, please upload new .blend file with all included data needed to reproduce that exact issue.

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RGB Curves node having an effect on components that they shouldn't. #48685