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ASTC compression in Unreal 4 not compressing HDR textures

Norman3DNorman3D Posts: 47
Lawnmower Man (or Woman)
This guide over here recommends using ASTC over ETC2. It makes perfect sense for my project as we are using quite a few HDR textures and ASTC is excellent at compressing these:

However I've noticed that Unreal 4 does not compress HDR textures at all with ASTC, I suspect because such functionality has not been implemented in the Cooker. Is this also the case with Oculus's branch of Unreal?

Best Answer


  • cyberealitycybereality Posts: 21,964 Oculus Staff
    Moving to Unreal Developer section.
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  • imperativityimperativity Posts: 1,182 Oculus Staff

    We don't encourage developers to use HDR on mobile, as there would be a large bandwidth cost.

  • Norman3DNorman3D Posts: 47
    Lawnmower Man (or Woman)

    We don't encourage developers to use HDR on mobile, as there would be a large bandwidth cost.

    This is not the same as mobile HDR (which is what I believe you are referring to.) This issue happens specifically with HDR textures. The issue is that Epic has not fully implemented ASTC, so HDR textures for example are not compressed causing a huge memory footprint. Compressed textures are totally fine on memory and on disk.
    My current workaround consist of using LogLuma encoding and saving it as an 8bit RGB. I then de-encode it in the shader. Unfortunately it costs me a bit on the pixel shader, which I would be able to avoid if ASTC HDR compression was implemented. I can still manage with the LogLuma encoding, it's just that I'd rather not use it if it was possible :)
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