Why is Red channel of Gray (packed texture) Previewing as RED?

UE4.27: Can the pros please help with 2 related problems. Ty.

The issue above is throwing me off because it’s making me think there is an error in my Material formula or if I am set to the wrong compression: sRGB vs Linear Color.

PreEdit: I found this question asking why the Red channel is previewing a gray texture as Red. But no answers, or any info why they changed this or how to turn it off.

My Details:

  1. I have a set of textures ripped from an old Unity game as PACKED textures = 32bit PNG with Alpha layer. And I have the Unity “Shader” formula (graph nodes) for how these textures act together to display correctly, which I am recreating in UE4 Material code.

  2. (I mention the “32bit” PNGs to note that I cannot and do not want to convert them to anything else because I have 100 – I want a solution as is by modifying my Material formula to work.)

  3. Problem 1: I dont know if I should batch edit all these textures’ Compression from sRGB (default import) to LinearColor (is this needed to use Gray packed channels)? - because the Material formula is wrong for some of these textures. (Thus Problem 2 – the red Preview is related to Problem 1.)

Problem 2:

  1. The “MetallicGloss” texture is packed with GRAY textures: R = Metallic, G = Emission, B = Roughness. There is no color in these channels – when I display the only R channel in UE4 texture window.


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  2. So why is the Preview of the R channel (In the Material window), showing a RED tone??? This is incorrect, it should display a black/white (gray) tone.


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  3. I searched and cannot find a modern answer.

  • I tried setting the Texture compression to “Masks” which means turn off sRGB > change to LinearColor.

  • But when I make a copy of “MetallicGloss” text, and set it to LinearColor, and plug it in the Material formula > R pin channel – the preview still shows a RED tone – when it is physically a gray texture. (This may be a cosmetic non issue that the other person asked about; but again, idk, and the unexpected Preview is throwing off my Material work since idk if my formula is correct so far.)

  • And I tried Material nodes: sRGBToLinear, and Desaturation - but the preview is still red (throwing me off). Ty.

This is the closest I got to an answer

It’s not going away…

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Thanks for the citation. So it appears to be cosmetic, and I wasnt doing things wrong. But that there probably isnt a cosmetic fix. But that’s dangerous because I also thought Desaturation node wasnt working - based on the flawed [colored Red] Preview.

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I hear you… :slight_smile: