Monochromatic roughnessMap texture and gpu ram optimisation

i’m using a loaded monochromatic roughnessMap texture and i’m wondering if there is a way to optimise vram storage of this bitmap.

is it revealent to configure like this ? :

roughnessMap.format = THREE.RedFormat;

is there a guide about texture format configuration / optimisation?

If VRAM is the goal I would consider:

(1) KTX2 / Basis Universal compression
(2) packing the roughness channel with metalness or AO if available

thanks for the informations.

what is the actual support of this ktx2/basis technology today ?

are there good exemples of workflows handling these compressed texture ?

is this gimp extension reliable ?

three.js supports textures with KTX2 compression. Generic tools like Photoshop or Blender probably do not. For workflows, see 3D-Formats-Guidelines/ at 3ee30b260cb6b397017532f483d86df44570e41d · KhronosGroup/3D-Formats-Guidelines · GitHub. I haven’t used the Gimp extension and can’t comment on that.