In the specification the format rg11b10ufloat is marked as not valid for render_attachment:

https://gpuweb.github.io/gpuweb/#plain-color-formats

We at Sketchfab/Epic have been using this format on WebGL2 as a render target for quite a long time, and have found it is very good for carrying HDR data through the postprocess/render pipeline. It is very convenient format to reduce gpu bandwidth with a very decent range.

Looking at vulkan (https://vulkan.gpuinfo.org/listoptimaltilingformats.php) and metal (https://developer.apple.com/metal/Metal-Feature-Set-Tables.pdf) it is a very well supported format for writing into. It is also a required color-renderable format for OpenglES 3.2.

We were wondering if this could be added to V1, or at least as an extension.