This patches refactors the compositor File Output mechanism and
implements the file output node for the Realtime Compositor. The
refactor was done for the following reasons:
1. The existing file output mechanism relied on a global EXR image
resource where the result of each compositor execution for each
view was accumulated and stored in the global resource, until the
last view is executed, when the EXR is finally saved. Aside from
relying on global resources, this can cause effective memory leaks
since the compositor can be interrupted before the EXR is written and
closed.
2. We need common code to share between all compositors since we now
have multiple compositor implementations.
3. We needed to take the opportunity to fix some of the issues with the
existing implementation, like lossy compression of data passes,
and inability to save single values passes.
The refactor first introduced a new structure called the Compositor
Render Context. This context stores compositor information related to
the render pipeline and is persistent across all compositor executions
of all views. Its extended lifetime relative to a single compositor
execution lends itself well to store data that is accumulated across
views. The context currently has a map of File Output objects. Those
objects wrap a Render Result structure and can be used to construct
multi-view images which can then be saved after all views are executed
using the existing BKE_image_render_write function.
Minor adjustments were made to the BKE and RE modules to allow saving
using the BKE_image_render_write function. Namely, the function now
allows the use of a source image format for saving as well as the
ability to not save the render result as a render by introducing two new
default arguments. Further, for multi-layer EXR saving, the existent of
a single unnamed render layer will omit the layer name from the EXR
channel full name, and only the pass, view, and channel ID will remain.
Finally, the Render Result to Image Buffer conversion now take he number
of channels into account, instead of always assuming color channels.
The patch implements the File Output node in the Realtime Compositor
using the aforementioned mechanisms, replaces the implementation of the
CPU compositor using the same Realtime Compositor implementation, and
setup the necessary logic in the render pipeline code.
Pull Request: https://projects.blender.org/blender/blender/pulls/113982
931c188ce5