In the 2020_R2 release of the GUI on macOS (Intel), the BC4/BC5/BC7 textures aren’t opening. Even generating these from an original png with mips, and then trying to re-open these fails with a message about an invalid or unsupported texture format. So far, only BC1 textures opened, but I don’t have BC3 data handy. It looks BC7 encoders are not available either.
Encoding a normal to BC5 snorm, ends up displaying a blank image in the GUI. Changing the range to 0 to 127 then makes the image visible. Maybe this isn’t using the full snorm range. This is the only way that I can view the file, and after saved to KTX, the file won’t open.
Also, the displayed scale of ETC2rg should be 11 bits (+/-2047), but the range displayed is +/-32K. This is a little confusing to compare normals in ETC2rg with ASTC/BC which use 8unorm and 8u/8snorm data. It might be useful here to display the normalized float values instead.
Included a test png image from some of the early id compression demos. This is a normal map that should wrap and display properly as BC5. This can be exported from the GUI tool, but then won’t reopen the file.
Here’s a ktx generated from the GUI.
collectorbarrel-pvr-n.ktx.zip (30.9 KB)