[Bf-committers] OpenEXR in Blender's CVS

Gernot Ziegler gz at lysator.liu.se
Sun Mar 13 13:51:32 CET 2005

Hejsan Ton !

> Now you've described the background of openEXR, but for the integration
> in Blender I'd like to see more info.
sure !

> 1) Coders level
> - why has openEXR become an optional #ifdeffed piece of code?
Kent wanted to introduce it as painlessly as possible.
It would be great to make it a fix part of the CVS, but then all platform
devs need to agree that this is no problem for them.

> - it seems like you (or kent) choose to integrate it like quicktime,
> e.g. a plugin that establishes connection runtime. Is that true? Why
> not compile in the static openEXR lib?
I have not thought about that, and I am not very good at static lib
integration (in regard to SCons and Makefile).

> - how is it integrated in the ImBuf for reading? Does it read "half" as
> well as 4x32 bits?
It only provides 4x8 bits. I don't know much about the loader's
possibilities, I can cooperate to extend them :-)

> 2) Installation level
> - is installing openEXR for users well documented on openexr.org, and
> is that monkey-proof for using Blender with it? For all platforms?
*checking OpenEXR for Win32, precompiled*
No, it isn't. Platform devs will need to provide info on how this is
done, or we could provide an easy-to-install package.

> - if the plugin isn't installed or found, how is that communicated?
> Does Blender run even without?
It is no plug-in per-se. If you compile with OpenEXR support, the binary
expects to find the .so's/DLLs. If not, then there is no OpenEXR
support and it is thus not showing up.
(I wouldn't want to change that, either. The third state that plugins
have, ie not finding their DLLs, makes things only more complicated)

> 3) Using it
> - how does EXR export react to settings like "B&W, RGB, RGBA" ?
It doesn't. It always exports RGBA.
That could be fixed if needed.
But since an OpenEXR loader can choose to ignore "A", at least RGB is not
(except for storage size, which is generally not an issue for OpenEXR
users, I think).

> - is only "half" supported for export now?
Yes, and that is what other applications expect first.
There is no main format for Z (I made it Half, for simplicity).

> - when is the Z layer exported?
As soon as the renderer provides Z data (which is always, I think).

> - are exported files compressed?
good question. I use the default behaviour, which implies lossless
compression, but I am not sure.


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