Blender Internal: Render tiles do not appear until render is finished if Save Buffers enabled #39029

System Information
64bit Linux Mint 16
Linux Kernel 3.11.0
nVidia GTX 650 Ti, driver 319.32

Blender Version
Broken: 2.70 Release Candidate 1
Worked: 2.69.0 r60991

Short description of error
When you Render a scene, the rendering tiles appear completely blank and remain so until the entire image is rendered. This only occurs if the "Save Buffers"

Exact steps for others to reproduce the error

Create a scene
Enable the "Save Buffers" setting under Performance.
Render

Changed status to: 'Open'

Added subscriber: @ZauberParacelsus

Added subscriber: @joel.godin

Not seeing that on OSX 10.9.2

Apparently I submitted before I was finished writing. The last sentence should read "This only occurs if the Save Buffers setting is enabled, under the Performance section of the Render tab."

Added subscriber: @ThomasDinges

Does not happen with Cycles, only Blender Internal.

Confirmed on Windows 7 x64, with latest master.

Added subscriber: @mont29

@ThomasDinges Even though it is present in Cycles UI, afaict Cycles completely ignores it, so I guess it could be removed from here?

Regarding BI, imho it’s not a bug - current code writes tiles into temp EXR files, and re-read it once render is finished, to display it in Blender. Reading EXR files after every tile is down could be done I guess, but not easily, and would kinda break the main purpose of this option (as we would have to keep one layer in memory during whole render). Assigning to Brecht anyway, to get its advice here!

Save buffers works for Cycles. If I had to guess then I think this is related to color management. It should be possible to have this preview work for BI too.

@mont29: It is an undesirable behavior that did not occur prior to 2.70. So it is not only a bug, it is also a regression.

Uh… well, then, the least I can do is fix it :/

@mont29: Sorry if I came down a little hard. Due to previous bad experiences in life, I get agitated whenever I feel like something I've said was ignored. So, my apologies.

Added subscriber: @Sergey

Gah… spent hours on this one, for a rather poor result… :/ So far:

Issue appeared in c5d7ea091 (but I do not see what’s the culprit it in this commit).
Issue is caused by temp renderresults used to generate preview (in e.g. RE_AcquireResultImage()) having neither rectf nor rect32 buffer, when using SaveBuffer.
When saving renderlayers in EXR instead of mem, code seems to allocate a dedicated buffer (in render_result_new(), rl->display_buffer), but never use it anywhere, as far as I can tell?

@Sergey, I think (hope!) you know/understand this stuff better than me, maybe it wouldn't be that hard for you to find a solution (or at least, understand what went wrong)?

This issue was referenced by blender/blender-addons-contrib@89c793f70f

This issue was referenced by 89c793f70f

Changed status from 'Open' to: 'Resolved'

Closed by commit 89c793f70f.

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Blender Internal: Render tiles do not appear until render is finished if Save Buffers enabled #39029