Yeah you're right. But just using exr 2.x isn't enough to
ensure multi-layered files are read fast. You have to save the
exr in a specific way.
Notes
on Rendering OpenEXR Files
Nuke supports multi-part OpenEXR 2.0.1
files, which allow you to store your channels, layers, and
views in separate parts of the file. Storing the data this
way can make loading .exr files faster, as Nuke
only has to access the part of the file that is requested
rather than all parts. However, for backwards compatibility,
you also have the option to render your .exr files
as single-part images.
To set how the data is stored in your rendered .exr
file, open the Write properties and set interleave
to:
• channels, layers and views
- Write channels, layers, and views into the same part of
the rendered .exr file. This creates a single-part
file to ensure backwards compatibility with earlier versions
of Nuke and other applications using an older
OpenEXR library.
• channels and layers -
Write channels and layers into the same part of the rendered
.exr file, but separate views into their own part.
This creates a multi-part file and can speed up Read
performance, as Nuke only has to access the
part of the file that is requested rather than all parts.
• channels - Separate
channels, layers, and views into their own parts of the
rendered .exr file. This creates a multi-part file
and can speed up Read performance if you work with only a
few layers at a time.
So to have the same speed with multi-layered exr that you
have with separate exr files, you have to use exr 2.x and only
then you have the choice to save a file in what Nuke call channels
and layers (fast) or channels (faster) mode.
But this breaks backwards compatibility so the files can not
be opened in applications that don't support exr 2.
