Compositor: Full-frame base system

This patch adds the base code needed to make the full-frame system work for both current tiled/per-pixel implementation of operations and full-frame.

Two execution models:
- Tiled: Current implementation. Renders execution groups in tiles from outputs to input. Not all operations are buffered. Runs the tiled/per-pixel implementation.
- FullFrame: All operations are buffered. Fully renders operations from inputs to outputs. Runs full-frame implementation of operations if available otherwise the current tiled/per-pixel. Creates output buffers on first read and free them as soon as all its readers have finished, reducing peak memory usage of complex/long trees. Operations are multi-threaded but do not run in parallel as Tiled (will be done in another patch).

This should allow us to convert operations to full-frame in small steps with the system already working and solve the problem of high memory usage.

FullFrame breaking changes respect Tiled system, mainly:
- Translate, Rotate, Scale, and Transform take effect immediately instead of next buffered operation.
- Any sampling is always done over inputs instead of last buffered operation.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D11113

1 files changed, 131 insertions, 0 deletions

diff --git a/source/blender/compositor/intern/COM_SharedOperationBuffers.cc b/source/blender/compositor/intern/COM_SharedOperationBuffers.cc
new file mode 100644
index 00000000000..021e948a727
--- /dev/null
+++ b/source/blender/compositor/intern/COM_SharedOperationBuffers.cc
@@ -0,0 +1,131 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Copyright 2021, Blender Foundation.
+ */
+
+#include "COM_SharedOperationBuffers.h"
+#include "BLI_rect.h"
+#include "COM_NodeOperation.h"
+
+namespace blender::compositor {
+
+SharedOperationBuffers::SharedOperationBuffers() : buffers_()
+{
+}
+SharedOperationBuffers::BufferData::BufferData()
+    : buffer(nullptr), render_areas(), registered_reads(0), received_reads(0)
+{
+}
+
+SharedOperationBuffers::BufferData &SharedOperationBuffers::get_buffer_data(NodeOperation *op)
+{
+  return buffers_.lookup_or_add_cb(op, []() { return BufferData(); });
+}
+
+/**
+ * Whether given operation area to render is already registered.
+ * TODO: Possibly refactor to "request_area". Current implementation is incomplete: partial
+ * overlapping, etc. Leading to more rendering than necessary.
+ */
+bool SharedOperationBuffers::is_area_registered(NodeOperation *op, const rcti &area_to_render)
+{
+  BufferData &buf_data = get_buffer_data(op);
+  for (rcti &reg_rect : buf_data.render_areas) {
+    if (BLI_rcti_inside_rcti(&reg_rect, &area_to_render)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/**
+ * Registers an operation area to render.
+ */
+void SharedOperationBuffers::register_area(NodeOperation *op, const rcti &area_to_render)
+{
+  get_buffer_data(op).render_areas.append(area_to_render);
+}
+
+/**
+ * Whether given operation has any registered reads (other operation registered it depends on given
+ * operation).
+ */
+bool SharedOperationBuffers::has_registered_reads(NodeOperation *op)
+{
+  return get_buffer_data(op).registered_reads > 0;
+}
+
+/**
+ * Registers an operation read (other operation depends on given operation).
+ */
+void SharedOperationBuffers::register_read(NodeOperation *read_op)
+{
+  get_buffer_data(read_op).registered_reads++;
+}
+
+/**
+ * Get registered areas given operation needs to render.
+ */
+blender::Span<rcti> SharedOperationBuffers::get_areas_to_render(NodeOperation *op)
+{
+  return get_buffer_data(op).render_areas.as_span();
+}
+
+/**
+ * Whether this operation buffer has already been rendered.
+ */
+bool SharedOperationBuffers::is_operation_rendered(NodeOperation *op)
+{
+  return get_buffer_data(op).buffer != nullptr;
+}
+
+/**
+ * Stores given operation rendered buffer.
+ */
+void SharedOperationBuffers::set_rendered_buffer(NodeOperation *op,
+                                                 std::unique_ptr<MemoryBuffer> buffer)
+{
+  BufferData &buf_data = get_buffer_data(op);
+  BLI_assert(buf_data.received_reads == 0);
+  BLI_assert(buf_data.buffer == nullptr);
+  buf_data.buffer = std::move(buffer);
+}
+
+/**
+ * Get given operation rendered buffer.
+ */
+MemoryBuffer *SharedOperationBuffers::get_rendered_buffer(NodeOperation *op)
+{
+  BLI_assert(is_operation_rendered(op));
+  return get_buffer_data(op).buffer.get();
+}
+
+/**
+ * Reports an operation has finished reading given operation. If all given operation dependencies
+ * have finished its buffer will be disposed.
+ */
+void SharedOperationBuffers::read_finished(NodeOperation *read_op)
+{
+  BufferData &buf_data = get_buffer_data(read_op);
+  buf_data.received_reads++;
+  BLI_assert(buf_data.received_reads > 0 && buf_data.received_reads <= buf_data.registered_reads);
+  if (buf_data.received_reads == buf_data.registered_reads) {
+    /* Dispose buffer. */
+    buf_data.buffer = nullptr;
+  }
+}
+
+}  // namespace blender::compositor