Creating an additional option for creating texture arrays instead of deducing from layer count

[toomuchvoltage]

Currently toktx seems to create arrayed textures only when layers is specified to be larger than one:

    createInfo.numLayers = options.layers;
    createInfo.isArray = options.layers > 1;

This causes issues when compressed textures are generated in bulk and assigned to various slots on a variable count descriptor set of sampler2DArrays. The issue mainly surfaces on AMD drivers (where the .z component of textureSize() ends up being undefined in the event the combined sampler is backed by a texture2D and not a texture2DArray).

I propose a separate option of --is-array that sets the flag inside KTX metadata to ensure that single layer texture arrays are possible (when potentially provided alongside larger/taller arrayed textures).

[MarkCallow]

Oops. --layers should have been used for arrays only. I wonder how many people actually use --layers 1 when not wanting an array. In other words, is it too late to change behavior now? If so, a new option will be needed.

[toomuchvoltage]

Thank you @MarkCallow for attending to this. Well I guess at this stage we might have to do a wider community poll?
(I can personally attest to being more responsive to the email surveys myself (if that is possible) 🙂)

[toomuchvoltage]

Hi @MarkCallow, hope all is well. Just wanted to check-in and see if you've made a decision either way regarding the tool. If so, please let me know so that I can align my local fix towards your preference in advance.

Much appreciate,
Baktash.

[MarkCallow]

I'm leaning towards using --layers. Its doc would change from

KTX file is for an array texture with number of layers where number > 1.

to

... number >= 1

I sent a survey to the Khronos WG responsible for KTX. I don't have a good place to make a general survey of users. I doubt most would see anything in the Wiki or GitHub questions.

[toomuchvoltage]

Perfect, thank you for the update: I'll assume that to be the new behavior. Hopefully, with a new update coming soon... I can just replace my build with yours. Much appreciated!

[MarkCallow]

I'm implementing this change. What behavior do you prefer when --layers 0 is specified on the command line:

1. silently create a non-array texture?
2. warn about possible mistake in option specification and create a non-array texture?
3. exit with an error?

[ghost]

Exit with an error, it was probably unintended.