Fix for #36468, "Buffer Groups" option changes compositing output.

Problem is that the read/write buffer operations only work with actual
image inputs. If a singular value is used as group input no actual
buffer will be created, the write operation does not schedule any chunks
and the ReadBufferOperation subsequently returns zero
(MemoryBuffer::read).

The fix uses the (0,0) resolution to detect single value input of the
WriteBufferOperation. The actual resolution is then clamped to (1,1) to
ensure we have a single pixel to store the value in. A m_single_value
flag is also set, so we can reliably distinguish this from genuine image
resolutions without having to check m_width/m_height later on.

The ReadBufferOperation copies this flag from the associated
WriteBufferOperation and if set will always return the single value from
pixel (0,0).

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/compositor/operations/COM_ReadBufferOperation.h b/source/blender/compositor/operations/COM_ReadBufferOperation.h
index 7e3ac147ee3..c8dcfb7c33d 100644
--- a/source/blender/compositor/operations/COM_ReadBufferOperation.h
+++ b/source/blender/compositor/operations/COM_ReadBufferOperation.h
@@ -29,6 +29,7 @@
 class ReadBufferOperation : public NodeOperation {
 private:
 	MemoryProxy *m_memoryProxy;
+	bool m_single_value; /* single value stored in buffer, copied from associated write operation */
 	unsigned int m_offset;
 	MemoryBuffer *m_buffer;
 public: