Refactor: Make viewport to use ViewRender

This change replaces a bare RenderEngine owned by a viewport
with a VeiwRender. This unlocks a possibility of accessing
RenderResult for viewport renders. Currently it is not done,
but it will be needed for an upcoming work towards unification
of the render passes handling.

Ref #108618

Pull Request: https://projects.blender.org/blender/blender/pulls/110244

source/blender/blenkernel/intern/paint.cc

@@ -2372,7 +2372,7 @@ bool BKE_sculptsession_use_pbvh_draw(const Object *ob, const RegionView3D *rv3d)
   if (BKE_pbvh_type(ss->pbvh) == PBVH_FACES) {
     /* Regular mesh only draws from PBVH without modifiers and shape keys, or for
      * external engines that do not have access to the PBVH like Eevee does. */
-    const bool external_engine = rv3d && rv3d->render_engine != nullptr;
+    const bool external_engine = rv3d && rv3d->view_render != nullptr;
     return !(ss->shapekey_active || ss->deform_modifiers_active || external_engine);
   }
 

source/blender/blenkernel/intern/screen.cc

@@ -1343,7 +1343,7 @@ static void direct_link_region(BlendDataReader *reader, ARegion *region, int spa
         BLO_read_data_address(reader, &rv3d->localvd);
         BLO_read_data_address(reader, &rv3d->clipbb);
 
-        rv3d->render_engine = nullptr;
+        rv3d->view_render = nullptr;
         rv3d->sms = nullptr;
         rv3d->smooth_timer = nullptr;
 

source/blender/draw/engines/external/external_engine.cc

@@ -244,16 +244,20 @@ static void external_draw_scene_do_v3d(void *vedata)
   GPU_apply_state();
 
   /* Create render engine. */
-  if (!rv3d->render_engine) {
+  RenderEngine *render_engine = nullptr;
+  if (!rv3d->view_render) {
     RenderEngineType *engine_type = draw_ctx->engine_type;
 
     if (!(engine_type->view_update && engine_type->view_draw)) {
       return;
     }
 
-    RenderEngine *engine = RE_engine_create(engine_type);
-    engine_type->view_update(engine, draw_ctx->evil_C, draw_ctx->depsgraph);
-    rv3d->render_engine = engine;
+    rv3d->view_render = RE_NewViewRender(engine_type);
+    render_engine = RE_view_engine_get(rv3d->view_render);
+    engine_type->view_update(render_engine, draw_ctx->evil_C, draw_ctx->depsgraph);
+  }
+  else {
+    render_engine = RE_view_engine_get(rv3d->view_render);
   }
 
   /* Rendered draw. */
@@ -262,8 +266,8 @@ static void external_draw_scene_do_v3d(void *vedata)
   ED_region_pixelspace(region);
 
   /* Render result draw. */
-  const RenderEngineType *type = rv3d->render_engine->type;
-  type->view_draw(rv3d->render_engine, draw_ctx->evil_C, draw_ctx->depsgraph);
+  const RenderEngineType *type = render_engine->type;
+  type->view_draw(render_engine, draw_ctx->evil_C, draw_ctx->depsgraph);
 
   GPU_bgl_end();
 
@@ -272,8 +276,8 @@ static void external_draw_scene_do_v3d(void *vedata)
 
   /* Set render info. */
   EXTERNAL_Data *data = static_cast<EXTERNAL_Data *>(vedata);
-  if (rv3d->render_engine->text[0] != '\0') {
-    STRNCPY(data->info, rv3d->render_engine->text);
+  if (render_engine->text[0] != '\0') {
+    STRNCPY(data->info, render_engine->text);
   }
   else {
     data->info[0] = '\0';

source/blender/editors/render/render_update.cc

@@ -72,7 +72,7 @@ void ED_render_view3d_update(Depsgraph *depsgraph,
 
     View3D *v3d = static_cast<View3D *>(area->spacedata.first);
     RegionView3D *rv3d = static_cast<RegionView3D *>(region->regiondata);
-    RenderEngine *engine = rv3d->render_engine;
+    RenderEngine *engine = rv3d->view_render ? RE_view_engine_get(rv3d->view_render) : nullptr;
 
     /* call update if the scene changed, or if the render engine
      * tagged itself for update (e.g. because it was busy at the

source/blender/editors/space_view3d/space_view3d.cc

@@ -216,7 +216,7 @@ void ED_view3d_stop_render_preview(wmWindowManager *wm, ARegion *region)
 {
   RegionView3D *rv3d = static_cast<RegionView3D *>(region->regiondata);
 
-  if (rv3d->render_engine) {
+  if (rv3d->view_render) {
 #ifdef WITH_PYTHON
     BPy_BEGIN_ALLOW_THREADS;
 #endif
@@ -227,8 +227,8 @@ void ED_view3d_stop_render_preview(wmWindowManager *wm, ARegion *region)
     BPy_END_ALLOW_THREADS;
 #endif
 
-    RE_engine_free(rv3d->render_engine);
-    rv3d->render_engine = nullptr;
+    RE_FreeViewRender(rv3d->view_render);
+    rv3d->view_render = nullptr;
   }
 
   /* A bit overkill but this make sure the viewport is reset completely. (fclem) */
@@ -1082,8 +1082,8 @@ static void view3d_main_region_free(ARegion *region)
       MEM_freeN(rv3d->clipbb);
     }
 
-    if (rv3d->render_engine) {
-      RE_engine_free(rv3d->render_engine);
+    if (rv3d->view_render) {
+      RE_FreeViewRender(rv3d->view_render);
     }
 
     if (rv3d->sms) {
@@ -1110,7 +1110,7 @@ static void *view3d_main_region_duplicate(void *poin)
       new_rv3d->clipbb = static_cast<BoundBox *>(MEM_dupallocN(rv3d->clipbb));
     }
 
-    new_rv3d->render_engine = nullptr;
+    new_rv3d->view_render = nullptr;
     new_rv3d->sms = nullptr;
     new_rv3d->smooth_timer = nullptr;
 

source/blender/editors/space_view3d/view3d_navigate_smoothview.cc

@@ -279,7 +279,7 @@ void ED_view3d_smooth_view_ex(
   }
 
   /* Skip smooth viewing for external render engine draw. */
-  if (smooth_viewtx && !(v3d->shading.type == OB_RENDER && rv3d->render_engine)) {
+  if (smooth_viewtx && !(v3d->shading.type == OB_RENDER && rv3d->view_render)) {
 
     /* original values */
     if (sview->camera_old) {

source/blender/makesdna/DNA_view3d_types.h

@@ -10,7 +10,7 @@
 
 struct BoundBox;
 struct Object;
-struct RenderEngine;
+struct ViewRender;
 struct SmoothView3DStore;
 struct SpaceLink;
 struct bGPdata;
@@ -58,7 +58,7 @@ typedef struct RegionView3D {
 
   /** Allocated backup of itself while in local-view. */
   struct RegionView3D *localvd;
-  struct RenderEngine *render_engine;
+  struct ViewRender *view_render;
 
   /** Animated smooth view. */
   struct SmoothView3DStore *sms;

source/blender/render/RE_engine.h

@@ -32,6 +32,7 @@ struct RenderResult;
 struct ReportList;
 struct Scene;
 struct ViewLayer;
+struct ViewRender;
 struct bNode;
 struct bNodeTree;
 
@@ -242,6 +243,7 @@ void RE_engine_register_pass(struct RenderEngine *engine,
 bool RE_engine_use_persistent_data(struct RenderEngine *engine);
 
 struct RenderEngine *RE_engine_get(const struct Render *re);
+struct RenderEngine *RE_view_engine_get(const struct ViewRender *view_render);
 
 /* Acquire render engine for drawing via its `draw()` callback.
  *

source/blender/render/RE_pipeline.h

@@ -160,6 +160,9 @@ struct Scene;
 struct Render *RE_NewSceneRender(const struct Scene *scene);
 struct Render *RE_GetSceneRender(const struct Scene *scene);
 
+struct RenderEngineType;
+struct ViewRender *RE_NewViewRender(struct RenderEngineType *engine_type);
+
 /* Assign default dummy callbacks. */
 
 /**
@@ -174,6 +177,7 @@ void RE_InitRenderCB(struct Render *re);
  * Only call this while you know it will remove the link too.
  */
 void RE_FreeRender(struct Render *re);
+void RE_FreeViewRender(struct ViewRender *view_render);
 /**
  * Only called on exit.
  */

source/blender/render/intern/engine.cc

@@ -1219,6 +1219,11 @@ RenderEngine *RE_engine_get(const Render *re)
   return re->engine;
 }
 
+RenderEngine *RE_view_engine_get(const ViewRender *view_render)
+{
+  return view_render->engine;
+}
+
 bool RE_engine_draw_acquire(Render *re)
 {
   RenderEngine *engine = re->engine;

source/blender/render/intern/pipeline.cc

@@ -507,6 +507,13 @@ Render *RE_NewRender(const char *name)
   return re;
 }
 
+ViewRender *RE_NewViewRender(RenderEngineType *engine_type)
+{
+  ViewRender *view_render = MEM_new<ViewRender>("new view render");
+  view_render->engine = RE_engine_create(engine_type);
+  return view_render;
+}
+
 /* MAX_ID_NAME + sizeof(Library->name) + space + null-terminator. */
 #define MAX_SCENE_RENDER_NAME (MAX_ID_NAME + 1024 + 2)
 
@@ -560,6 +567,11 @@ void RE_FreeRender(Render *re)
   MEM_delete(re);
 }
 
+void RE_FreeViewRender(ViewRender *view_render)
+{
+  MEM_delete(view_render);
+}
+
 void RE_FreeAllRender()
 {
   while (!RenderGlobal.render_list.empty()) {

source/blender/render/intern/render_types.h

@@ -53,6 +53,9 @@ struct BaseRender {
   ThreadMutex engine_draw_mutex = BLI_MUTEX_INITIALIZER;
 };
 
+struct ViewRender : public BaseRender {
+};
+
 /* Controls state of render, everything that's read-only during render stage */
 struct Render : public BaseRender {
   /* NOTE: Currently unused, provision for the future.

source/blender/windowmanager/intern/wm_draw.c

@@ -406,7 +406,7 @@ static bool wm_draw_region_stereo_set(Main *bmain,
         View3D *v3d = area->spacedata.first;
         if (v3d->camera && v3d->camera->type == OB_CAMERA) {
           RegionView3D *rv3d = region->regiondata;
-          RenderEngine *engine = rv3d->render_engine;
+          RenderEngine *engine = rv3d->view_render ? RE_view_engine_get(rv3d->view_render) : NULL;
           if (engine && !(engine->type->flag & RE_USE_STEREO_VIEWPORT)) {
             return false;
           }
@@ -495,7 +495,7 @@ static void wm_region_test_render_do_draw(const Scene *scene,
   /* tag region for redraw from render engine preview running inside of it */
   if (area->spacetype == SPACE_VIEW3D && region->regiontype == RGN_TYPE_WINDOW) {
     RegionView3D *rv3d = region->regiondata;
-    RenderEngine *engine = rv3d->render_engine;
+    RenderEngine *engine = rv3d->view_render ? RE_view_engine_get(rv3d->view_render) : NULL;
     GPUViewport *viewport = WM_draw_region_get_viewport(region);
 
     if (engine && (engine->flag & RE_ENGINE_DO_DRAW)) {