Update Basis Universal to 1.6.0 and ktx-parse to support UASTC 6x6 HDR

[hybridherbst]

Description

Follow-up to #31689.

After realizing that three.js currently ships with basis 1.5, I updated locally to 1.6 and can now load more of the test files:

However, my wasm build is 635kB instead of the previous 515kB, so I'm somewhat reluctant to make a PR with that, assuming I missed some optimizations.

The last image in the row is 2d_astc_hdr6x6i.ktx2 (intermediate format, must be transcoded to either ASTC or BC6H). To load it, likely an update of ktx-parse is needed.

Solution

Update basis_transcoder and ktx-parse to support UASTC 6x6 HDR

Alternatives

Additional context

No response

[hybridherbst]

Related:

• KTX2Loader: Upgrade to Basis Universal v1.50 #29418
• Fix: bring back -O3 in LINK_FLAGS for 150kB smaller JS+WASM build BinomialLLC/basis_universal#401

There seems to be a considerable size increase in basis from 1.50 (53 KB JS + 527 KB WASM) to 1.60 (106 KB JS + 669 KB WASM). With the change linked above it's down to 53 KB JS + 620 KB WASM.

[donmccurdy]

Thanks @hybridherbst! Appreciate your looking into the linking flags. Do you have the gzip size on the wasm by any chance?

I'd probably lean toward keeping the Basis Universal library up to date here, even if the size is larger than we'd like. We could consider other transcoders in the future, too, but that's not a blocker now. If the -O3 size optimization can be restored, all the better. :)