Improvements and fixes to Cycles metadata

This is a request by the studio here to make it possible to see how
many samples were used to render a specific shot or a frame. It is a
bit more tricky than simply stamping number of samples from a scene
since rendering is happening in multiple ranges of samples.

This change makes it so Cycles saves configured number of samples for
the specific view layer, and also stores start sample and number of
samples when rendering only a subrange of all samples.

The format used is "cycles.<view_layer_name>.><field>", which allows
to have information about all layers in a multi-layer EXR file.

Ideally we can store simplified "cycles.<field>" if we know that there
is only one render layer in the file, but detecting this is somewhat
tricky since Cycles operates on an evaluated scene which always have
single view layer.

The metadata is shown in the Metadata panels for clip, image and
sequencer spaces.

Example screenshot which shows the metadata:

{F6527727}

Reviewers: brecht

Reviewed By: brecht

Subscribers: fsiddi

Differential Revision: https://developer.blender.org/D4311

1 files changed, 4 insertions, 0 deletions

diff --git a/source/blender/imbuf/IMB_metadata.h b/source/blender/imbuf/IMB_metadata.h
index df26682a466..72b5a95287c 100644
--- a/source/blender/imbuf/IMB_metadata.h
+++ b/source/blender/imbuf/IMB_metadata.h
@@ -66,4 +66,8 @@ void IMB_metadata_set_field(struct IDProperty *metadata, const char *key, const
 void IMB_metadata_copy(struct ImBuf *dimb, struct ImBuf *simb);
 struct IDProperty *IMB_anim_load_metadata(struct anim *anim);
 
+/* Invoke callback for every value stored in the metadata. */
+typedef void (*IMBMetadataForeachCb)(const char *field, const char *value, void *userdata);
+void IMB_metadata_foreach(struct ImBuf *ibuf, IMBMetadataForeachCb callback, void *userdata);
+
 #endif /* __IMB_METADATA_H__ */