Re: [Openexr-user] EXR layer naming conventions

[Jim Hourihan]

On Jul 5, 2007, at 4:26 PM, address@hidden wrote:

> Some of the examples you mention seem like they would make more  
> sense as per-layer attributes rather than per-channel attributes.  
> For example a camera matrix, or units for things like normal and  
> vector layers. (If something like a camera matrix weren't specified  
> per-layer then readers would need to be able to handle cases like  
> some channels not having the attribute or some having inconsistent  
> values.)
>
> Implementation-wise, do you think that it would be preferable to  
> have new attribute types which themselves could store lists of  
> attributes (similar to "chlist"), or to use the top-level list of  
> attributes and recognize "." notation in attribute names? e.g.:

Your idea seems like it would do the trick. Since we're already  
assuming channel names with dots are in a layer hierarchy, applying  
that same convention to attribute names gives us channel and layer  
attributes right now. (Assuming its ok to use dots in an attribute  
name). Any API like the layer API would be gravy.

> And of course all of this would require a set of recommended  
> mappings to be useful. This is still somewhat divorced from the  
> previous discussion about how much guidance the spec should provide  
> regarding channel and layer naming *unless* if the set of  
> recommended mappings were so complete as to render channel/layer  
> names inconsequential.

Agreed. But maybe we just want a "best practices" document for film.  
I know EXR is being used in other settings (like NASA) and my guess  
is that they have a completely different set of issues to deal with  
(e.g., 7 "color" channel images).

        -Jim