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No Hq Compression For Rgb Textures?

Discussion in 'General Graphics' started by Warrior1424, Apr 15, 2019.

  1. Warrior1424

    Warrior1424

    Joined:
    Sep 30, 2010
    Posts:
    980
    Currently using Unity 2018.3.12f1, target is PC.

    If I have a 1K texture that is RGBA, it remains 1.3MB on both high and medium quality compression.

    If I have a 1K texture that is merely RGB, it begins as 0.7MB but jumps to 1.3MB after moving it from medium to high quality compression because it has to have an alpha channel with that compression format (RGB(A) Compressed BC7).


    Is there really no high quality compression format for RGB, only RGBA?
    Do other platforms have this problem, or only desktop?
     
  2. bgolus

    bgolus

    Joined:
    Dec 7, 2012
    Posts:
    6,247
    BC7 is a high quality RGB format. It gets that higher quality by being twice the size of BC1 (DXT1). BC7 can switch its format from RGB to RGBA based on the contents of each 4x4 block. Areas with alpha have lower quality RGB (generally better than DXT5, though not always), but those blocks with out are much higher quality.
     
  3. Warrior1424

    Warrior1424

    Joined:
    Sep 30, 2010
    Posts:
    980
    That makes a lot of sense. Thank you as always, @bgolus .