Dark stripes rendering .PSD image texture in cycles #75221

New Issue

Sebastien Larocque · 2020-03-30T19:57:54+02:00

2020-03-30 19:57:54 +02:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.28

Blender Version
Broken: version: 2.83 (sub 11), branch: master, commit date: 2020-03-29 21:36, hash: a103d09df4

Short description of error

There is a banding (or line) effect in Cycles when using transparent gradient textures with attached file.
Image color data contains a bit darker stripes, that aren't in original image file, but given that eevee doesn't exhibit this bug this may not be only problem here.

Exact steps for others to reproduce the error

Open the .blend file attached.
Set the viewport shading to "Display render preview" (with Cycles) or do a render of the scene.
The banding effect becomes more apparent when zooming in.
The scene object “Gradient01” has the material “Gradient01” with the sRBG color-space texture.
To fix, the problem, someone can change the color space of the image node to Non-Color or Raw. Linear color space has the same kind of effect as sRGB, but less apparent.
As the gradient fades out to more transparency, there are darker bands appearing at different regular intervals.

{F8437251 size=full}

Cycles - Alpha Banding.blend

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.28 **Blender Version** Broken: version: 2.83 (sub 11), branch: master, commit date: 2020-03-29 21:36, hash: `a103d09df4` **Short description of error** There is a banding (or line) effect in Cycles when using transparent gradient textures with attached file. Image color data contains a bit darker stripes, that aren't in original image file, but given that eevee doesn't exhibit this bug this may not be only problem here. **Exact steps for others to reproduce the error** * Open the .blend file attached. * Set the viewport shading to "Display render preview" (with Cycles) or do a render of the scene. * The banding effect becomes more apparent when zooming in. * The scene object “Gradient01” has the material “Gradient01” with the sRBG color-space texture. * To fix, the problem, someone can change the color space of the image node to Non-Color or Raw. Linear color space has the same kind of effect as sRGB, but less apparent. * As the gradient fades out to more transparency, there are darker bands appearing at different regular intervals. {[F8437251](https://archive.blender.org/developer/F8437251/AlphaBanding.png) size=full} ![Gradient01.psd](https://archive.blender.org/developer/F8437248/Gradient01.psd) [Cycles - Alpha Banding.blend](https://archive.blender.org/developer/F8437249/Cycles_-_Alpha_Banding.blend)

Sebastien Larocque commented

2020-03-30 19:57:54 +02:00

Added subscriber: @SebBlender

Richard Antalik commented

2020-04-01 11:06:35 +02:00

Added subscriber: @iss

Richard Antalik commented

2020-04-01 11:06:35 +02:00

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

Richard Antalik commented

2020-04-01 11:06:35 +02:00

When looking at pixel values in image editor, you can see that color data is not correct.
PNG doesn't have this issue in this case.

When looking at pixel values in image editor, you can see that color data is not correct. PNG doesn't have this issue in this case.

Richard Antalik changed title from ~~sRBG color space in image node creates banding effects with alpha/transparent gradients~~ to Dark stripes rendering .PSD image in cycles

2020-04-01 11:18:01 +02:00

Richard Antalik changed title from ~~Dark stripes rendering .PSD image in cycles~~ to Dark stripes rendering .PSD image texture in cycles

2020-04-01 11:18:26 +02:00

Bastien Montagne commented

2020-04-06 16:39:55 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2020-04-06 16:39:55 +02:00

Am not sure how well we support PSD files… Thhink it’s through OpenImageIO currently?

Anyway, this belongs to #vfx_video project, not to #data_assets_i_o one imho.

Am not sure how well we support PSD files… Thhink it’s through OpenImageIO currently? Anyway, this belongs to #vfx_video project, not to #data_assets_i_o one imho.

Brecht Van Lommel commented

2020-05-13 21:16:10 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2020-05-13 21:16:10 +02:00

Changed status from 'Confirmed' to: 'Archived'

Brecht Van Lommel closed this issue

2020-05-13 21:16:10 +02:00

Brecht Van Lommel self-assigned this 2020-05-13 21:16:10 +02:00

Brecht Van Lommel commented

2020-05-13 21:16:10 +02:00

These artifacts are already present in the PSD file, which presumably is compressed or was created from a compressed image. If you look at the alpha channel in the image editor and zoom in you can see this is not actually a smooth gradient.

The artifact shows up as "banding" because the pixels are stretched very wide on this mesh.

These artifacts are already present in the PSD file, which presumably is compressed or was created from a compressed image. If you look at the alpha channel in the image editor and zoom in you can see this is not actually a smooth gradient. The artifact shows up as "banding" because the pixels are stretched very wide on this mesh.

Richard Antalik commented

2020-05-14 16:24:11 +02:00

In #75221#930927, @brecht wrote:
These artifacts are already present in the PSD file, which presumably is compressed or was created from a compressed image. If you look at the alpha channel in the image editor and zoom in you can see this is not actually a smooth gradient.

The artifact shows up as "banding" because the pixels are stretched very wide on this mesh.

I think, that issue is that this .PSD file is incorrectly imported. When viewed in gimp gradient is actually smooth and color has value of 1 for all pixels.

> In #75221#930927, @brecht wrote: > These artifacts are already present in the PSD file, which presumably is compressed or was created from a compressed image. If you look at the alpha channel in the image editor and zoom in you can see this is not actually a smooth gradient. > > The artifact shows up as "banding" because the pixels are stretched very wide on this mesh. I think, that issue is that this .PSD file is incorrectly imported. When viewed in gimp gradient is actually smooth and color has value of 1 for all pixels.

Brecht Van Lommel commented

2020-05-14 16:52:25 +02:00

I see the same artifacts in the alpha channel in GIMP. Colors > Components > Decompose, then choose Alpha.

Richard Antalik commented

2020-05-14 17:01:36 +02:00

Ah sorry you are correct. I must have screwed up extracting this channel.

Sebastien Larocque commented

2020-05-14 19:53:38 +02:00

I also tried to decompose the alpha channel in Gimp and I do not get any stripes. Everything looks normal to me.

What should provide a clue about the source of the problem is the color space of the texture node that I tested as mentioned initially in my report. Changing from sRGB to Non-Color space solves the problem. So far, it’s the only solution or workaround to this problem.

Furthermore, Eeve does not have this problem. If it was really in the PSD file, I presume that Eeve would render the image with the same information.

I created another project to test the alpha channel in Blender. I used the same texture “Gradient01.psd”. I created another object "Gradient02" where I used an opaque black and white color ramp where the value is influenced by the alpha channel of the gradient texture in the same sRGB color space. The result is a perfect progressive gradient.

To me the alpha channel seems correct. I could not find any problem outside Blender and it seems related to the use of the color space and the PSD file. Maybe the library used to read the PSD file has a bug. Is this provided by Adobe?

Maybe this has a connection with the color profile found in the PSD file.

Cycles - Alpha Banding2.blend

I also tried to decompose the alpha channel in Gimp and I do not get any stripes. Everything looks normal to me. What should provide a clue about the source of the problem is the color space of the texture node that I tested as mentioned initially in my report. Changing from sRGB to Non-Color space solves the problem. So far, it’s the only solution or workaround to this problem. Furthermore, Eeve does not have this problem. If it was really in the PSD file, I presume that Eeve would render the image with the same information. I created another project to test the alpha channel in Blender. I used the same texture “Gradient01.psd”. I created another object "Gradient02" where I used an opaque black and white color ramp where the value is influenced by the alpha channel of the gradient texture in the same sRGB color space. The result is a perfect progressive gradient. To me the alpha channel seems correct. I could not find any problem outside Blender and it seems related to the use of the color space and the PSD file. Maybe the library used to read the PSD file has a bug. Is this provided by Adobe? Maybe this has a connection with the color profile found in the PSD file. [Cycles - Alpha Banding2.blend](https://archive.blender.org/developer/F8535772/Cycles_-_Alpha_Banding2.blend)

Brecht Van Lommel commented

2020-05-15 00:42:21 +02:00

Cycles texture interpolation is intentionally different (following typical offline renderers, while Eevee follows game engines). That means alpha is premultiplied before interpolation, and will affect color channels.

Changing color spaces will also mask such issues, as it may round values.

I see the same noise in the alpha channel in macOS preview. I see no reason to assume there is a problem in PSD file reading.

In any case PSD is a poor file format for texture mapping. While it should generally work, we won't invest much time in investigating corner cases like this.

Cycles texture interpolation is intentionally different (following typical offline renderers, while Eevee follows game engines). That means alpha is premultiplied before interpolation, and will affect color channels. Changing color spaces will also mask such issues, as it may round values. I see the same noise in the alpha channel in macOS preview. I see no reason to assume there is a problem in PSD file reading. In any case PSD is a poor file format for texture mapping. While it should generally work, we won't invest much time in investigating corner cases like this.

Sebastien Larocque commented

2020-05-15 02:44:37 +02:00

I don’t understand all the mechanics behind Blender. You seem to understand quite well. However, there are a couple of things to rectify.

You marked my report as “invalid”. I disagree with that. The problem is real. I agree that it might not be a priority when you consider other issues being reported.

There are other software like ACDSee which read properly the PSD file format with transparency. I assume there are ways to handle this.

The fact that you describe PSD as a poor file format is something very subjective. I don’t consider PSD being poor. Among the image formats with layers, it’s the most popular. It’s also very convenient to be able to modify the PSD file and just reload the file in Blender instead of doing an export every time to a PNG. It saves some time. It’s also widely used by the game engine Unity because of its characteristics with layers.

My recommendation is to keep my report valid, but instead assign a priority that respect the rest of your development. This would certainly be more useful for me if that worked, but the final decision is yours.

I don’t understand all the mechanics behind Blender. You seem to understand quite well. However, there are a couple of things to rectify. You marked my report as “invalid”. I disagree with that. The problem is real. I agree that it might not be a priority when you consider other issues being reported. There are other software like ACDSee which read properly the PSD file format with transparency. I assume there are ways to handle this. The fact that you describe PSD as a poor file format is something very subjective. I don’t consider PSD being poor. Among the image formats with layers, it’s the most popular. It’s also very convenient to be able to modify the PSD file and just reload the file in Blender instead of doing an export every time to a PNG. It saves some time. It’s also widely used by the game engine Unity because of its characteristics with layers. My recommendation is to keep my report valid, but instead assign a priority that respect the rest of your development. This would certainly be more useful for me if that worked, but the final decision is yours.

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Dark stripes rendering .PSD image texture in cycles #75221