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Strange things in the grayscale textures pipeline


I try to use uncompressed grayscale textures and I got results I don't understand. My textures are to be used for vertex displacement and I need to keep the highest quality possible. So to me the best choice is the G8 compression format. I also uncheck the sRGB parameter in the Texture options because those textures are not for visualization. Beside if the sRGB checkbox is checked the compression format switches back to B8G8R8A8. So in the texture editor the texture is displayed exactly as I see it in Photoshop and as I expect it to be.

The thing is when I import it in the shader editor the texture sampler is in Linear Grayscale and the look is awful (as if corrected with a gamma). If I set the sampler to Grayscale I got an error on the Texture Sample node.

So my questions are: - why the preview of the texture differs from the Texture Editor and the Shader Editor? - why can't I use a linear sampling?

By the way my texture has been imported as a grayscale image in png format because the grayscale tga format returns an error at import time. Isn't tga format supposed to be fully supported?

Thanks a lot

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asked Dec 26 '14 at 10:09 PM in Rendering

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avatar image Lovecraft_K ♦♦ STAFF Dec 29 '14 at 05:20 PM

Hey werwack -

Would it be possible to post the PNG file here for me to test with? If you would like to keep it private please feel free to message it to me via the Private Message on the Forums.

Thank You

Eric Ketchum

avatar image Lovecraft_K ♦♦ STAFF Jan 05 '15 at 02:38 PM

Hi werwack,

We have not heard back from you in a few days, so we are marking this post as Resolved for tracking purposes. If you are still experiencing the issue you reported, please respond to this message with additional information and we will offer further assistance.

Thank you.

Eric Ketchum

avatar image werwack Jan 06 '15 at 08:07 AM

Hi Eric,

I thank you very much for your help and apologize for my late answer.

You will find attached my sample image (the one I was taking about and use for a water ripple displacement on a mesh surface) as well as some commented screens to illustrate my confusion.

I guess my confusion comes from the fact that the thumbnails in the shader editor do proceed to a systematic gamma correction whereas they probably should respect the specified sampler. This leads to an uncomfortable editing environment because some parts of the edited shader have a look that doesn't reflect the way the texture is used. For example: how can I trust the settings of my greyscale texture while I develop my shader if the thumbnail looks like it does in the screen 1? We loose quite a lot of time and confidence by double-checking the texture settings every time we have to work with greyscale images.

Please feel free to ask me more details if you need so.

By the way, would it be possible to support 8 bits tga textures?

Thanks a lot,


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avatar image werwack Jan 09 '15 at 10:45 AM

Hi Eric,

Have you had time to have a look at my request? I would be pleased to have a better understanding about how a greyscale texture workflow should be handled.

Thank you very much

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Hey werwack -

I have asked our engineers to look closer at this issue as a possible bug, for reference UE-7379. As soon as I hear back from them I will let you know.

Thank You for your patience -

Eric Ketchum

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answered Jan 09 '15 at 10:14 PM

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Lovecraft_K ♦♦ STAFF
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avatar image werwack Jan 18 '15 at 07:55 PM

Hi Eric,

Thank you for your consideration for this issue. I see your latest comment has been flagged as an answer, but what is the solution exactly? Is there really a bug? Will it be fixed?

I look forward to hearing from you,

Best regards,


avatar image Luos Jan 18 '15 at 11:11 PM

In the meantime you could use the radial gradient node (plus some tweaks) to get the same grayscale but without the need of a texture.

avatar image Lovecraft_K ♦♦ STAFF Jan 19 '15 at 05:21 PM

Hey werwack -

Yes it appears to be an issue to me so I have escalated it to our rendering engineers who are currently looking into it. I should also note that this issue is one of visualization and not a rendering error in the final product. We are looking into why the texture editor and material editor visualizations are differing. I am uncertain as of yet when there will be a fix but one will be developed and as soon as I hear anything I will post back here.

Thank You

Eric Ketchum

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