Realtime Compositor: Add evaluator and engine

This patch adds the core realtime compositor evaluator as well as a
compositor draw engine powered by the evaluator that operates in the
viewport. The realtime compositor is a new GPU accelerated compositor
that will be used to power the viewport compositor imminently as well as
the existing compositor in the future.

This patch only adds the evaluator and engine as an experimental
feature, the implementation of the nodes themselves will be committed
separately.

See T99210.

Differential Revision: https://developer.blender.org/D15206

Reviewed By: Clement Foucault

4 files changed, 253 insertions, 1 deletions

diff --git a/source/blender/draw/CMakeLists.txt b/source/blender/draw/CMakeLists.txt
index ec57c302b31..391c3bb3512 100644
--- a/source/blender/draw/CMakeLists.txt
+++ b/source/blender/draw/CMakeLists.txt
@@ -23,6 +23,7 @@ set(INC
   ../nodes
   ../render
   ../render/intern
+  ../compositor/realtime_compositor
   ../windowmanager
 
   ../../../intern/atomic
@@ -103,6 +104,7 @@ set(SRC
   intern/smaa_textures.c
   engines/basic/basic_engine.c
   engines/basic/basic_shader.c
+  engines/compositor/compositor_engine.cc
   engines/image/image_engine.cc
   engines/image/image_shader.cc
   engines/eevee/eevee_bloom.c
@@ -231,6 +233,7 @@ set(SRC
   intern/smaa_textures.h
   engines/basic/basic_engine.h
   engines/basic/basic_private.h
+  engines/compositor/compositor_engine.h
   engines/eevee/eevee_engine.h
   engines/eevee/eevee_lightcache.h
   engines/eevee/eevee_lut.h
@@ -262,6 +265,7 @@ set(SRC
 set(LIB
   bf_blenkernel
   bf_blenlib
+  bf_realtime_compositor
   bf_windowmanager
 )
 
diff --git a/source/blender/draw/engines/compositor/compositor_engine.cc b/source/blender/draw/engines/compositor/compositor_engine.cc
new file mode 100644
index 00000000000..b3fcf0505cb
--- /dev/null
+++ b/source/blender/draw/engines/compositor/compositor_engine.cc
@@ -0,0 +1,203 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "BLI_listbase.h"
+#include "BLI_math_vec_types.hh"
+#include "BLI_string_ref.hh"
+#include "BLI_utildefines.h"
+
+#include "BLT_translation.h"
+
+#include "DNA_ID_enums.h"
+#include "DNA_scene_types.h"
+
+#include "DEG_depsgraph_query.h"
+
+#include "DRW_render.h"
+
+#include "IMB_colormanagement.h"
+
+#include "COM_context.hh"
+#include "COM_evaluator.hh"
+#include "COM_texture_pool.hh"
+
+#include "GPU_texture.h"
+
+namespace blender::draw::compositor {
+
+class TexturePool : public realtime_compositor::TexturePool {
+ public:
+  GPUTexture *allocate_texture(int2 size, eGPUTextureFormat format) override
+  {
+    DrawEngineType *owner = (DrawEngineType *)this;
+    return DRW_texture_pool_query_2d(size.x, size.y, format, owner);
+  }
+};
+
+class Context : public realtime_compositor::Context {
+ private:
+  /* A pointer to the info message of the compositor engine. This is a char array of size
+   * GPU_INFO_SIZE. The message is cleared prior to updating or evaluating the compositor. */
+  char *info_message_;
+
+ public:
+  Context(realtime_compositor::TexturePool &texture_pool, char *info_message)
+      : realtime_compositor::Context(texture_pool), info_message_(info_message)
+  {
+  }
+
+  const Scene *get_scene() const override
+  {
+    return DRW_context_state_get()->scene;
+  }
+
+  int2 get_output_size() override
+  {
+    return int2(float2(DRW_viewport_size_get()));
+  }
+
+  GPUTexture *get_output_texture() override
+  {
+    return DRW_viewport_texture_list_get()->color;
+  }
+
+  GPUTexture *get_input_texture(int UNUSED(view_layer), eScenePassType UNUSED(pass_type)) override
+  {
+    return get_output_texture();
+  }
+
+  StringRef get_view_name() override
+  {
+    const SceneRenderView *view = static_cast<SceneRenderView *>(
+        BLI_findlink(&get_scene()->r.views, DRW_context_state_get()->v3d->multiview_eye));
+    return view->name;
+  }
+
+  void set_info_message(StringRef message) const override
+  {
+    message.copy(info_message_, GPU_INFO_SIZE);
+  }
+};
+
+class Engine {
+ private:
+  TexturePool texture_pool_;
+  Context context_;
+  realtime_compositor::Evaluator evaluator_;
+  /* Stores the viewport size at the time the last compositor evaluation happened. See the
+   * update_viewport_size method for more information. */
+  int2 last_viewport_size_;
+
+ public:
+  Engine(char *info_message)
+      : context_(texture_pool_, info_message),
+        evaluator_(context_, node_tree()),
+        last_viewport_size_(context_.get_output_size())
+  {
+  }
+
+  /* Update the viewport size and evaluate the compositor. */
+  void draw()
+  {
+    update_viewport_size();
+    evaluator_.evaluate();
+  }
+
+  /* If the size of the viewport changed from the last time the compositor was evaluated, update
+   * the viewport size and reset the evaluator. That's because the evaluator compiles the node tree
+   * in a manner that is specifically optimized for the size of the viewport. This should be called
+   * before evaluating the compositor. */
+  void update_viewport_size()
+  {
+    if (last_viewport_size_ == context_.get_output_size()) {
+      return;
+    }
+
+    last_viewport_size_ = context_.get_output_size();
+
+    evaluator_.reset();
+  }
+
+  /* If the compositor node tree changed, reset the evaluator. */
+  void update(const Depsgraph *depsgraph)
+  {
+    if (DEG_id_type_updated(depsgraph, ID_NT)) {
+      evaluator_.reset();
+    }
+  }
+
+  /* Get a reference to the compositor node tree. */
+  static bNodeTree &node_tree()
+  {
+    return *DRW_context_state_get()->scene->nodetree;
+  }
+};
+
+}  // namespace blender::draw::compositor
+
+using namespace blender::draw::compositor;
+
+typedef struct COMPOSITOR_Data {
+  DrawEngineType *engine_type;
+  DRWViewportEmptyList *fbl;
+  DRWViewportEmptyList *txl;
+  DRWViewportEmptyList *psl;
+  DRWViewportEmptyList *stl;
+  Engine *instance_data;
+  char info[GPU_INFO_SIZE];
+} COMPOSITOR_Data;
+
+static void compositor_engine_init(void *data)
+{
+  COMPOSITOR_Data *compositor_data = static_cast<COMPOSITOR_Data *>(data);
+
+  if (!compositor_data->instance_data) {
+    compositor_data->instance_data = new Engine(compositor_data->info);
+  }
+}
+
+static void compositor_engine_free(void *instance_data)
+{
+  Engine *engine = static_cast<Engine *>(instance_data);
+  delete engine;
+}
+
+static void compositor_engine_draw(void *data)
+{
+  const COMPOSITOR_Data *compositor_data = static_cast<COMPOSITOR_Data *>(data);
+  compositor_data->instance_data->draw();
+}
+
+static void compositor_engine_update(void *data)
+{
+  COMPOSITOR_Data *compositor_data = static_cast<COMPOSITOR_Data *>(data);
+
+  /* Clear any info message that was set in a previous update. */
+  compositor_data->info[0] = '\0';
+
+  if (compositor_data->instance_data) {
+    compositor_data->instance_data->update(DRW_context_state_get()->depsgraph);
+  }
+}
+
+extern "C" {
+
+static const DrawEngineDataSize compositor_data_size = DRW_VIEWPORT_DATA_SIZE(COMPOSITOR_Data);
+
+DrawEngineType draw_engine_compositor_type = {
+    nullptr,                   /* next */
+    nullptr,                   /* prev */
+    N_("Compositor"),          /* idname */
+    &compositor_data_size,     /* vedata_size */
+    &compositor_engine_init,   /* engine_init */
+    nullptr,                   /* engine_free */
+    &compositor_engine_free,   /* instance_free */
+    nullptr,                   /* cache_init */
+    nullptr,                   /* cache_populate */
+    nullptr,                   /* cache_finish */
+    &compositor_engine_draw,   /* draw_scene */
+    &compositor_engine_update, /* view_update */
+    nullptr,                   /* id_update */
+    nullptr,                   /* render_to_image */
+    nullptr,                   /* store_metadata */
+};
+}
diff --git a/source/blender/draw/engines/compositor/compositor_engine.h b/source/blender/draw/engines/compositor/compositor_engine.h
new file mode 100644
index 00000000000..5de0de8a0b3
--- /dev/null
+++ b/source/blender/draw/engines/compositor/compositor_engine.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern DrawEngineType draw_engine_compositor_type;
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/source/blender/draw/intern/draw_manager.c b/source/blender/draw/intern/draw_manager.c
index 63c7cc667cb..b965045a424 100644
--- a/source/blender/draw/intern/draw_manager.c
+++ b/source/blender/draw/intern/draw_manager.c
@@ -43,6 +43,7 @@
 #include "DNA_camera_types.h"
 #include "DNA_mesh_types.h"
 #include "DNA_meshdata_types.h"
+#include "DNA_userdef_types.h"
 #include "DNA_world_types.h"
 
 #include "ED_gpencil.h"
@@ -84,6 +85,7 @@
 #include "draw_cache_impl.h"
 
 #include "engines/basic/basic_engine.h"
+#include "engines/compositor/compositor_engine.h"
 #include "engines/eevee/eevee_engine.h"
 #include "engines/eevee_next/eevee_engine.h"
 #include "engines/external/external_engine.h"
@@ -1214,6 +1216,31 @@ static void drw_engines_enable_editors(void)
   }
 }
 
+static bool is_compositor_enabled(void)
+{
+  if (!U.experimental.use_realtime_compositor) {
+    return false;
+  }
+
+  if (!(DST.draw_ctx.v3d->shading.flag & V3D_SHADING_COMPOSITOR)) {
+    return false;
+  }
+
+  if (!(DST.draw_ctx.v3d->shading.type > OB_MATERIAL)) {
+    return false;
+  }
+
+  if (!DST.draw_ctx.scene->use_nodes) {
+    return false;
+  }
+
+  if (!DST.draw_ctx.scene->nodetree) {
+    return false;
+  }
+
+  return true;
+}
+
 static void drw_engines_enable(ViewLayer *UNUSED(view_layer),
                                RenderEngineType *engine_type,
                                bool gpencil_engine_needed)
@@ -1226,6 +1253,11 @@ static void drw_engines_enable(ViewLayer *UNUSED(view_layer),
   if (gpencil_engine_needed && ((drawtype >= OB_SOLID) || !use_xray)) {
     use_drw_engine(&draw_engine_gpencil_type);
   }
+
+  if (is_compositor_enabled()) {
+    use_drw_engine(&draw_engine_compositor_type);
+  }
+
   drw_engines_enable_overlays();
 
 #ifdef WITH_DRAW_DEBUG
@@ -1597,7 +1629,6 @@ void DRW_draw_render_loop_ex(struct Depsgraph *depsgraph,
                              GPUViewport *viewport,
                              const bContext *evil_C)
 {
-
   Scene *scene = DEG_get_evaluated_scene(depsgraph);
   ViewLayer *view_layer = DEG_get_evaluated_view_layer(depsgraph);
   RegionView3D *rv3d = region->regiondata;
@@ -2948,6 +2979,7 @@ void DRW_engines_register(void)
   DRW_engine_register(&draw_engine_overlay_type);
   DRW_engine_register(&draw_engine_select_type);
   DRW_engine_register(&draw_engine_basic_type);
+  DRW_engine_register(&draw_engine_compositor_type);
 #ifdef WITH_DRAW_DEBUG
   DRW_engine_register(&draw_engine_debug_select_type);
 #endif