Cycles: optimize device updates

This optimizes device updates (during user edits or frame changes in
the viewport) by avoiding unnecessary computations. To achieve this,
we use a combination of the sockets' update flags as well as some new
flags passed to the various managers when tagging for an update to tell
exactly what the tagging is for (e.g. shader was modified, object was
removed, etc.).

Besides avoiding recomputations, we also avoid resending to the devices
unmodified data arrays, thus reducing bandwidth usage. For OptiX and
Embree, BVH packing was also multithreaded.

The performance improvements may vary depending on the used device (CPU
or GPU), and the content of the scene. Simple scenes (e.g. with no adaptive
subdivision or volumes) rendered using OptiX will benefit from this work
the most.

On average, for a variety of animated scenes, this gives a 3x speedup.

Reviewed By: #cycles, brecht

Maniphest Tasks: T79174

Differential Revision: https://developer.blender.org/D9555

1 files changed, 107 insertions, 29 deletions

diff --git a/intern/cycles/render/object.cpp b/intern/cycles/render/object.cpp
index 406982e3ef9..0f16a4fc12c 100644
--- a/intern/cycles/render/object.cpp
+++ b/intern/cycles/render/object.cpp
@@ -153,6 +153,10 @@ void Object::update_motion()
 
 void Object::compute_bounds(bool motion_blur)
 {
+  if (!is_modified() && !geometry->is_modified()) {
+    return;
+  }
+
   BoundBox mbounds = geometry->bounds;
 
   if (motion_blur && use_motion()) {
@@ -205,20 +209,39 @@ void Object::apply_transform(bool apply_to_motion)
 
 void Object::tag_update(Scene *scene)
 {
+  uint32_t flag = ObjectManager::UPDATE_NONE;
+
+  if (is_modified()) {
+    flag |= ObjectManager::OBJECT_MODIFIED;
+
+    if (use_holdout_is_modified()) {
+      flag |= ObjectManager::HOLDOUT_MODIFIED;
+    }
+  }
+
   if (geometry) {
-    if (geometry->transform_applied)
-      geometry->tag_modified();
+    if (tfm_is_modified()) {
+      /* tag the geometry as modified so the BVH is updated, but do not tag everything as modified
+       */
+      if (geometry->is_mesh() || geometry->is_volume()) {
+        Mesh *mesh = static_cast<Mesh *>(geometry);
+        mesh->tag_verts_modified();
+      }
+      else if (geometry->is_hair()) {
+        Hair *hair = static_cast<Hair *>(geometry);
+        hair->tag_curve_keys_modified();
+      }
+    }
 
     foreach (Node *node, geometry->get_used_shaders()) {
       Shader *shader = static_cast<Shader *>(node);
       if (shader->get_use_mis() && shader->has_surface_emission)
-        scene->light_manager->need_update = true;
+        scene->light_manager->tag_update(scene, LightManager::EMISSIVE_MESH_MODIFIED);
     }
   }
 
   scene->camera->need_flags_update = true;
-  scene->geometry_manager->need_update = true;
-  scene->object_manager->need_update = true;
+  scene->object_manager->tag_update(scene, flag);
 }
 
 bool Object::use_motion() const
@@ -361,7 +384,7 @@ int Object::get_device_index() const
 
 ObjectManager::ObjectManager()
 {
-  need_update = true;
+  update_flags = UPDATE_ALL;
   need_flags_update = true;
 }
 
@@ -382,7 +405,9 @@ static float object_volume_density(const Transform &tfm, Geometry *geom)
   return 1.0f;
 }
 
-void ObjectManager::device_update_object_transform(UpdateObjectTransformState *state, Object *ob)
+void ObjectManager::device_update_object_transform(UpdateObjectTransformState *state,
+                                                   Object *ob,
+                                                   bool update_all)
 {
   KernelObject &kobject = state->objects[ob->index];
   Transform *object_motion_pass = state->object_motion_pass;
@@ -456,8 +481,11 @@ void ObjectManager::device_update_object_transform(UpdateObjectTransformState *s
       kobject.motion_offset = state->motion_offset[ob->index];
 
       /* Decompose transforms for interpolation. */
-      DecomposedTransform *decomp = state->object_motion + kobject.motion_offset;
-      transform_motion_decompose(decomp, ob->motion.data(), ob->motion.size());
+      if (ob->tfm_is_modified() || update_all) {
+        DecomposedTransform *decomp = state->object_motion + kobject.motion_offset;
+        transform_motion_decompose(decomp, ob->motion.data(), ob->motion.size());
+      }
+
       flag |= SD_OBJECT_MOTION;
       state->have_motion = true;
     }
@@ -480,10 +508,14 @@ void ObjectManager::device_update_object_transform(UpdateObjectTransformState *s
                          0;
   kobject.patch_map_offset = 0;
   kobject.attribute_map_offset = 0;
-  uint32_t hash_name = util_murmur_hash3(ob->name.c_str(), ob->name.length(), 0);
-  uint32_t hash_asset = util_murmur_hash3(ob->asset_name.c_str(), ob->asset_name.length(), 0);
-  kobject.cryptomatte_object = util_hash_to_float(hash_name);
-  kobject.cryptomatte_asset = util_hash_to_float(hash_asset);
+
+  if (ob->asset_name_is_modified() || update_all) {
+    uint32_t hash_name = util_murmur_hash3(ob->name.c_str(), ob->name.length(), 0);
+    uint32_t hash_asset = util_murmur_hash3(ob->asset_name.c_str(), ob->asset_name.length(), 0);
+    kobject.cryptomatte_object = util_hash_to_float(hash_name);
+    kobject.cryptomatte_asset = util_hash_to_float(hash_asset);
+  }
+
   kobject.shadow_terminator_offset = 1.0f / (1.0f - 0.5f * ob->shadow_terminator_offset);
 
   /* Object flag. */
@@ -544,6 +576,9 @@ void ObjectManager::device_update_transforms(DeviceScene *dscene, Scene *scene,
     numparticles += psys->particles.size();
   }
 
+  /* as all the arrays are the same size, checking only dscene.objects is sufficient */
+  const bool update_all = dscene->objects.need_realloc();
+
   /* Parallel object update, with grain size to avoid too much threading overhead
    * for individual objects. */
   static const int OBJECTS_PER_TASK = 32;
@@ -551,7 +586,7 @@ void ObjectManager::device_update_transforms(DeviceScene *dscene, Scene *scene,
                [&](const blocked_range<size_t> &r) {
                  for (size_t i = r.begin(); i != r.end(); i++) {
                    Object *ob = state.scene->objects[i];
-                   device_update_object_transform(&state, ob);
+                   device_update_object_transform(&state, ob, update_all);
                  }
                });
 
@@ -559,7 +594,7 @@ void ObjectManager::device_update_transforms(DeviceScene *dscene, Scene *scene,
     return;
   }
 
-  dscene->objects.copy_to_device();
+  dscene->objects.copy_to_device_if_modified();
   if (state.need_motion == Scene::MOTION_PASS) {
     dscene->object_motion_pass.copy_to_device();
   }
@@ -569,6 +604,10 @@ void ObjectManager::device_update_transforms(DeviceScene *dscene, Scene *scene,
 
   dscene->data.bvh.have_motion = state.have_motion;
   dscene->data.bvh.have_curves = state.have_curves;
+
+  dscene->objects.clear_modified();
+  dscene->object_motion_pass.clear_modified();
+  dscene->object_motion.clear_modified();
 }
 
 void ObjectManager::device_update(Device *device,
@@ -576,12 +615,28 @@ void ObjectManager::device_update(Device *device,
                                   Scene *scene,
                                   Progress &progress)
 {
-  if (!need_update)
+  if (!need_update())
     return;
 
+  if (update_flags & (OBJECT_ADDED | OBJECT_REMOVED)) {
+    dscene->objects.tag_realloc();
+    dscene->object_motion_pass.tag_realloc();
+    dscene->object_motion.tag_realloc();
+    dscene->object_flag.tag_realloc();
+    dscene->object_volume_step.tag_realloc();
+  }
+
+  if (update_flags & HOLDOUT_MODIFIED) {
+    dscene->object_flag.tag_modified();
+  }
+
+  if (update_flags & PARTICLE_MODIFIED) {
+    dscene->objects.tag_modified();
+  }
+
   VLOG(1) << "Total " << scene->objects.size() << " objects.";
 
-  device_free(device, dscene);
+  device_free(device, dscene, false);
 
   if (scene->objects.size() == 0)
     return;
@@ -597,6 +652,16 @@ void ObjectManager::device_update(Device *device,
     int index = 0;
     foreach (Object *object, scene->objects) {
       object->index = index++;
+
+      /* this is a bit too broad, however a bigger refactor might be needed to properly separate
+       * update each type of data (transform, flags, etc.) */
+      if (object->is_modified()) {
+        dscene->objects.tag_modified();
+        dscene->object_motion_pass.tag_modified();
+        dscene->object_motion.tag_modified();
+        dscene->object_flag.tag_modified();
+        dscene->object_volume_step.tag_modified();
+      }
     }
   }
 
@@ -638,7 +703,7 @@ void ObjectManager::device_update(Device *device,
 void ObjectManager::device_update_flags(
     Device *, DeviceScene *dscene, Scene *scene, Progress & /*progress*/, bool bounds_valid)
 {
-  if (!need_update && !need_flags_update)
+  if (!need_update() && !need_flags_update)
     return;
 
   scoped_callback_timer timer([scene](double time) {
@@ -647,7 +712,7 @@ void ObjectManager::device_update_flags(
     }
   });
 
-  need_update = false;
+  update_flags = UPDATE_NONE;
   need_flags_update = false;
 
   if (scene->objects.size() == 0)
@@ -717,6 +782,9 @@ void ObjectManager::device_update_flags(
   /* Copy object flag. */
   dscene->object_flag.copy_to_device();
   dscene->object_volume_step.copy_to_device();
+
+  dscene->object_flag.clear_modified();
+  dscene->object_volume_step.clear_modified();
 }
 
 void ObjectManager::device_update_mesh_offsets(Device *, DeviceScene *dscene, Scene *scene)
@@ -764,13 +832,13 @@ void ObjectManager::device_update_mesh_offsets(Device *, DeviceScene *dscene, Sc
   }
 }
 
-void ObjectManager::device_free(Device *, DeviceScene *dscene)
+void ObjectManager::device_free(Device *, DeviceScene *dscene, bool force_free)
 {
-  dscene->objects.free();
-  dscene->object_motion_pass.free();
-  dscene->object_motion.free();
-  dscene->object_flag.free();
-  dscene->object_volume_step.free();
+  dscene->objects.free_if_need_realloc(force_free);
+  dscene->object_motion_pass.free_if_need_realloc(force_free);
+  dscene->object_motion.free_if_need_realloc(force_free);
+  dscene->object_flag.free_if_need_realloc(force_free);
+  dscene->object_volume_step.free_if_need_realloc(force_free);
 }
 
 void ObjectManager::apply_static_transforms(DeviceScene *dscene, Scene *scene, Progress &progress)
@@ -841,11 +909,21 @@ void ObjectManager::apply_static_transforms(DeviceScene *dscene, Scene *scene, P
   }
 }
 
-void ObjectManager::tag_update(Scene *scene)
+void ObjectManager::tag_update(Scene *scene, uint32_t flag)
+{
+  update_flags |= flag;
+
+  /* avoid infinite loops if the geometry manager tagged us for an update */
+  if ((flag & GEOMETRY_MANAGER) == 0) {
+    scene->geometry_manager->tag_update(scene, GeometryManager::OBJECT_MANAGER);
+  }
+
+  scene->light_manager->tag_update(scene, LightManager::OBJECT_MANAGER);
+}
+
+bool ObjectManager::need_update() const
 {
-  need_update = true;
-  scene->geometry_manager->need_update = true;
-  scene->light_manager->need_update = true;
+  return update_flags != UPDATE_NONE;
 }
 
 string ObjectManager::get_cryptomatte_objects(Scene *scene)