When Oodle Texture Compression is used with the high compression amount (30), we observe than corruption is introduced to the alpha channel of a specific texture. We haven’t observed this with other source textures, or at compression amounts either higher or lower than 30. I’ve reproduced this in a vanilla 5.6.1 Editor.
Steps to Reproduce
- Using a vanilla 5.6.1 Editor, import the supplied texture with the following Oodle settings [Image Removed]
- Observe corruption in the alpha channel
- Observe that corruption disappears if the Oodle compression amount is changed to 20 or lower, or to 40
- Observe that corruption disappears if the target texture size is reduced to 1024
What texture format and what Oodle version is this?
Never mind, figured it out, just didn’t see it correctly because I had the texture editor zoomed out. 
This is an overflow issue that happens in some very specific circumstances. It’s fixed in Oodle Texture 2.9.15, which should ship in UE 5.8.
In the meantime, if you hit this again and need a workaround, as you already discovered you can either change the RDO Lambda setting on the texture slightly (e.g. 28 or 31 instead of 30) or just disabled RDO on that texture entirely. (Set “Lossy Compression Amount” in the Advanced Compression Settings to “No lossy compression (Oodle RDO disabled)”).
Hi, thanks for the info. We’ve only observed this affecting one texture so far, but if it becomes more prevalent in our project it might be worth it for us to integrate Oodle Texture 2.9.15 before 5.8.
This bug has shipped in all Oodle Texture versions ever, it’s not a recent bug, so it’s unlikely to be common, we’d have noticed this before.
Anyway, confirmed bug, fix is forthcoming, I’ll close this for now! If you do end up running into it more frequently and need a better workaround or an early 2.9.15 drop, feel free to open another support case.