KTX Basis textures fail to load on all iOS browsers

[DerrickBarra]

Hi @atteneder , new bug report for ya.

On WebGL export projects, KTXUnity is loading some textures as black (no error, but not being displayed properly). Happens on our iPhone SE 2020 and iPhone 12 pro max. This happens on Safari, Chrome, and Firefox for iOS.

Using Chrome://inspect on iOS Chrome browser, you can see my OnSuccess messages for KTXUnity are firing off, I also have error debug logs in this project, but Unity thinks everything is fine and I'm only seeing success callbacks.

Built using Unity 2020.1.1f1, WebGL 1.0, uncompressed (no brotli or gzip compression). KTXUnity is set to 1.0.0 from February 03, 2021.

Check out our test Project, loading a bunch of .basis textures from an Amazon S3 bucket.

I'll update this thread if I find out anything else about this. From memory, this wasn't happening on older versions of KTXUnity, but I'll keep investigating. Let me know if you've ever seen this bug or can confirm it on your end!

[DerrickBarra]

@atteneder I've created a new repo for testing this bug, you can access it here.

[atteneder]

Hi @DerrickBarra ,

Thanks for the detailed report plus test repo. I'm still on paternity leave so I won't fix it soon, but I'll have a look in the next weeks.

[atteneder]

I observed that Safari is quite picky when it comes to textures. Is the resolution of the non-working textures by chance:

• non power of two
• non multiple of four
• non square

and do they come with mipmaps?

If not, please try to adhere to those rules and try them again.

[DerrickBarra]

@atteneder so looking at one of the textures that failed to load, the rabbit in the magic hat...

Here's a link to the .basis version.

This is a 1024x1024 image (divisible by 2, multiple of 4, square, no mipmaps). And it should be working...

---

So as a sanity test, I retested the project on my iOS SE 2020 and now everything works as expected even after multiple cache clearings, so I guess Apple released a Safari update that fixed it? That's nice!

[atteneder]

Great to hear!

In KtxUnity 1.1.0 I fixed a bug that potentially caused this trouble, but when I tested on my iOS devices, I still ran into troubles (but only on non-square non-multiple-of-four).

I'm waiting on 2021.2 (which will support WebGL mobile) to fix a build/linking error. After that I'll do more tests on iOS 14/15 before I call this one closed.

Thanks for your feedback

[kyapp69]

Despite the various standards, iOS devices will only support square and power of 2 multiple of four textures, I think this is due to compatibility with metal apis

[atteneder]

Yeah, today I also ran into problems on macOS-metal with non-multiple-of-4 textures and BC7

[atteneder]

I just tested a dev version of the upcoming 2.2.0 release and it worked successfully on iOS 16 and iPadOS 15.7 respectively.

This version chooses formats differently, so that might have solved it (or the iOS updates).

Will close this ticket now. Releases imminent