Fix T64953: Add cryptomatte meta data to file output node.

This change will try to add meta data when using a multilayered open
exr file output node in the compositor. It adds the current scene meta
data and converts existing cryptomatte keys so it follows the
naming that is configured in the file output node.

This change supports the basic use-case where the compositor is
used to output cryptomatte layers with a different naming scheme to
support external compositors. In this case the Multilayered OpenEXR
files are used and the meta data is read from the render result.

Meta data is found when render layer node is connected with the
file output node without any other nodes in between. Redirects and empty
node groups are allowed.

The patch has been verified to work with external compositors.
See https://devtalk.blender.org/t/making-sense-of-cryptomatte-usage-in-third-party-programs/16576/17

See patch for example files.

Reviewed By: Sergey Sharybin

Differential Revision: https://developer.blender.org/D10016

1 files changed, 13 insertions, 0 deletions

diff --git a/source/blender/compositor/intern/COM_SocketReader.h b/source/blender/compositor/intern/COM_SocketReader.h
index ee2a6e0e1bf..7c4132efe60 100644
--- a/source/blender/compositor/intern/COM_SocketReader.h
+++ b/source/blender/compositor/intern/COM_SocketReader.h
@@ -19,8 +19,12 @@
 #pragma once
 
 #include "BLI_rect.h"
+#include "COM_MetaData.h"
 #include "COM_defines.h"
 
+#include <memory>
+#include <optional>
+
 #ifdef WITH_CXX_GUARDEDALLOC
 #  include "MEM_guardedalloc.h"
 #endif
@@ -32,6 +36,7 @@ typedef enum PixelSampler {
 } PixelSampler;
 
 class MemoryBuffer;
+
 /**
  * \brief Helper class for reading socket data.
  * Only use this class for dispatching (un-ary and n-ary) executions.
@@ -134,6 +139,14 @@ class SocketReader {
     return this->m_height;
   }
 
+  /* Return the meta data associated with this branch.
+   *
+   * The return parameter holds an instance or is an nullptr. */
+  virtual std::unique_ptr<MetaData> getMetaData() const
+  {
+    return std::unique_ptr<MetaData>();
+  }
+
 #ifdef WITH_CXX_GUARDEDALLOC
   MEM_CXX_CLASS_ALLOC_FUNCS("COM:SocketReader")
 #endif