テンプレート:Release Notes/2.42/Image/OpenEXR

OpenEXR

OpenEXR finally in Blender!

Credits go to Gernot Ziegler, who originally coded EXR support, and to AustinBenesh for bringing it further. Kent Mein provided a lot of code for integrating float buffers in Blender imbuf and ImBuf API cleanup, and provided Make and Scons and static linking.

At this moment; the EXR libraries are a *dependency*, so you cannot get the Orange branch compiled without having OpenEXR installed. Get the (precompiled or sources) stuff from www.openexr.com. Current default is that the headers and lib resides in /user/local/

Several changes/additions/fixes were added:

- EXR code only supported 'half' format (16 bits per channel). I've added float writing, but for reading it I need tomorrow. :) - Quite some clumsy copying of data happened in EXR code. - cleaned up the api calls already a bit, preparing for more advanced support - Zbuffers were saved 16 bits, now 32 bits - automatic adding of .exr extensions went wrong

Imbuf:

- added proper imbuf->flags and imbuf->mall support for float buffers, it was created for *each* imbuf. :) - found bugs for float buffers in scaling and flipping. Code there will need more checks still - imbuf also needs to be verified to behave properly when no 32 bits rect exists (for saving for example)

TODO:

- support internal float images for textures, backbuf, AO probes, and display in Image window

Orange OpenEXR

Further cleanup of EXR saving

- F10 scene buttons now has options "half" and "zbuf" for exr saving. Note: when no float buffer is available, it always saves as "half", that's sufficient anyway, since half is 16 bits per channel.

- EXR in imbuf now uses compliant ibuf->ftype flags for denoting exr extensions such as 'half' and 'compression'.

- Removed ugly blenkernel dependency from exr module

- Reading exr images now goes OK. I've unified the code for reading 'half' and 'float' (was nicely possible!). And removed useless copying of data around.

- Fixed bug in allocating new rects, like for making mipmaps. flag issues.

- filter code accidentally incremented wrong pointer (crash on mipmap too)

and now for the real exr fun: float buffer support in Image window!

Image as loaded in Blender (from openexr.com): http://www.blender.org/bf/exrcurve1.jpg

Image with different white point: http://www.blender.org/bf/exrcurve2.jpg

Image with white and black point and a curve: http://www.blender.org/bf/exrcurve3.jpg

Use SHIFT+click to set the black point, and CTRL+click for white point. The buttons in the panel work too, of course.

The curves work after the black/white range was corrected, so you can stick to curves with a normal 0-1 range. There's also now a general color curve, marked with 'C' button.

Note; this currently only maps the float colors to a visible 8 bits per channel rect. You can save it, but when the blender file loads the curve or mapping is not executed until you click in the curves... have to look at that still. Speed for this is also quite unoptimized... still WIP, but fun!

Orange more openexr

more work on float/exr buffers;

- EXR now saves and reads Zbuffers correctly - EXR reading didn't set alpha to 1 yet when no alpha buffer was present

- ImageWindow: the "black point" only checked for the r value... now is OK - ImageWindow: Curves panal has button "reset" - ImageWindow: hold LMB drag shows rgba and z values. With SHIFT or CTRL it applies black/white point whilte dragging too - ImageWindow: saving file copied the entire buffer... removed that. Also made the header print clear; this save only saves in own file type.

- Curves: zoom and drag now gets clamped by the Clipping value

- Imbuf: duplicate buffer only copied one quarter of to new buffer

Orange exr

Orange: tested all EXR demo images from openexr.com, found two issues;

- images with a so-called "data window" (have negative start coordinate) did not read correctly - negative colors were not clamped yet in imbuf

Now there's still some compliancy issues with zbuffers... you can save it either as unsigned int or as float, whilst blender renders zbuffer in signed int. :)

Orange: more float buffer support;

- Image textures use float colors now, when present. Works for mipmap too, and for AO skycolor (probes) - Backbuffer option uses float buffers too. Note that rendering OSA will resample the backbuffer, filtering it... will need to be solved with the new composit stage - LMB sampling in image window now shows float color too

+ bugfix in imbuf, filtering for float buffers had an error.

openexr

 Log:
 Work in progress commit on saving OpenEXR with all render-layers and
 passes in single file. Code is currently disabled, commit is mainly to
 have a nicer method of excluding OpenEXR dependency from render module.
 This should compile with disabled WITH_OPENEXR too.
 
 Reason why EXR is great to include by default in Blender is its feature
 to store unlimited layers and channels, and write this tile based. I
 need the feature for saving memory; while rendering tiles, all full-size
 buffers for all layers and passes are kept in memory now, which can go
 into 100s of MB easily.
 The code I commit now doesn't allocate these buffers while rendering, but
 saves the tiles to disk. In the end is it read back. Overhead for large
 renders (like 300 meg buffers) is 10-15 seconds, not bad.
 
 Two more interesting aspects:
 - Blender can save such multi-layer files in the temp directory, storing
 it with .blend file name and scene name. That way, on each restart of Blender,
 or on switching scenes, these buffers can be read. So you always see what was
 rendered last. Also great for compositing work.
 - This can also become an output image type for rendering. There's plenty of
 cases where you want specific layers or passes saved to disk for later use.
 
 Anyhoo, finishing it is another days of work, and I got more urgent stuff
 now!