Geometry Nodes: support for geometry instancing

Previously, the Point Instance node in geometry nodes could only instance
existing objects or collections. The reason was that large parts of Blender
worked under the assumption that objects are the main unit of instancing.
Now we also want to instance geometry within an object, so a slightly larger
refactor was necessary.

This should not affect files that do not use the new kind of instances.

The main change is a redefinition of what "instanced data" is. Now, an
instances is a cow-object + object-data (the geometry). This can be nicely
seen in `struct DupliObject`. This allows the same object to generate
multiple geometries of different types which can be instanced individually.

A nice side effect of this refactor is that having multiple geometry components
is not a special case in the depsgraph object iterator anymore, because those
components are integrated with the `DupliObject` system.

Unfortunately, different systems that work with instances in Blender (e.g.
render engines and exporters) often work under the assumption that objects are
the main unit of instancing. So those have to be updated as well to be able to
handle the new instances. This patch updates Cycles, EEVEE and other viewport
engines. Exporters have not been updated yet. Some minimal (not master-ready)
changes to update the obj and alembic exporters can be found in P2336 and P2335.
Different file formats may want to handle these new instances in different ways.

For users, the only thing that changed is that the Point Instance node now
has a geometry mode.

This also fixes T88454.

Differential Revision: https://developer.blender.org/D11841

5 files changed, 151 insertions, 23 deletions

diff --git a/source/blender/blenkernel/intern/geometry_component_instances.cc b/source/blender/blenkernel/intern/geometry_component_instances.cc
index 3b1b7456162..26ef827d36d 100644
--- a/source/blender/blenkernel/intern/geometry_component_instances.cc
+++ b/source/blender/blenkernel/intern/geometry_component_instances.cc
@@ -122,7 +122,7 @@ blender::Span<int> InstancesComponent::instance_ids() const
  * If the reference exists already, the handle of the existing reference is returned.
  * Otherwise a new handle is added.
  */
-int InstancesComponent::add_reference(InstanceReference reference)
+int InstancesComponent::add_reference(const InstanceReference &reference)
 {
   return references_.index_of_or_add_as(reference);
 }
@@ -144,14 +144,23 @@ bool InstancesComponent::is_empty() const
 
 bool InstancesComponent::owns_direct_data() const
 {
-  /* The object and collection instances are not direct data. Instance transforms are direct data
-   * and are always owned. Therefore, instance components always own all their direct data. */
+  for (const InstanceReference &reference : references_) {
+    if (!reference.owns_direct_data()) {
+      return false;
+    }
+  }
   return true;
 }
 
 void InstancesComponent::ensure_owns_direct_data()
 {
   BLI_assert(this->is_mutable());
+  for (const InstanceReference &const_reference : references_) {
+    /* Const cast is fine because we are not changing anything that would change the hash of the
+     * reference. */
+    InstanceReference &reference = const_cast<InstanceReference &>(const_reference);
+    reference.ensure_owns_direct_data();
+  }
 }
 
 static blender::Array<int> generate_unique_instance_ids(Span<int> original_ids)
diff --git a/source/blender/blenkernel/intern/geometry_set.cc b/source/blender/blenkernel/intern/geometry_set.cc
index 07b4e715ea9..dafebef1812 100644
--- a/source/blender/blenkernel/intern/geometry_set.cc
+++ b/source/blender/blenkernel/intern/geometry_set.cc
@@ -218,6 +218,16 @@ void GeometrySet::ensure_owns_direct_data()
   }
 }
 
+bool GeometrySet::owns_direct_data() const
+{
+  for (const GeometryComponentPtr &component : components_.values()) {
+    if (!component->owns_direct_data()) {
+      return false;
+    }
+  }
+  return true;
+}
+
 /* Returns a read-only mesh or null. */
 const Mesh *GeometrySet::get_mesh_for_read() const
 {
@@ -376,9 +386,32 @@ void BKE_geometry_set_free(GeometrySet *geometry_set)
   delete geometry_set;
 }
 
-bool BKE_geometry_set_has_instances(const GeometrySet *geometry_set)
+bool BKE_object_has_geometry_set_instances(const Object *ob)
 {
-  return geometry_set->get_component_for_read<InstancesComponent>() != nullptr;
+  const GeometrySet *geometry_set = ob->runtime.geometry_set_eval;
+  if (geometry_set == nullptr) {
+    return false;
+  }
+  if (geometry_set->has_instances()) {
+    return true;
+  }
+  const bool has_mesh = geometry_set->has_mesh();
+  const bool has_pointcloud = geometry_set->has_pointcloud();
+  const bool has_volume = geometry_set->has_volume();
+  const bool has_curve = geometry_set->has_curve();
+  if (ob->type == OB_MESH) {
+    return has_pointcloud || has_volume || has_curve;
+  }
+  if (ob->type == OB_POINTCLOUD) {
+    return has_mesh || has_volume || has_curve;
+  }
+  if (ob->type == OB_VOLUME) {
+    return has_mesh || has_pointcloud || has_curve;
+  }
+  if (ob->type == OB_CURVE) {
+    return has_mesh || has_pointcloud || has_volume;
+  }
+  return false;
 }
 
 /** \} */
diff --git a/source/blender/blenkernel/intern/geometry_set_instances.cc b/source/blender/blenkernel/intern/geometry_set_instances.cc
index 32a65ab47bf..376792b9b96 100644
--- a/source/blender/blenkernel/intern/geometry_set_instances.cc
+++ b/source/blender/blenkernel/intern/geometry_set_instances.cc
@@ -168,6 +168,11 @@ static void geometry_set_collect_recursive(const GeometrySet &geometry_set,
               collection, instance_transform, r_sets);
           break;
         }
+        case InstanceReference::Type::GeometrySet: {
+          const GeometrySet &geometry_set = reference.geometry_set();
+          geometry_set_collect_recursive(geometry_set, instance_transform, r_sets);
+          break;
+        }
         case InstanceReference::Type::None: {
           break;
         }
@@ -290,6 +295,13 @@ static bool instances_attribute_foreach_recursive(const GeometrySet &geometry_se
         }
         break;
       }
+      case InstanceReference::Type::GeometrySet: {
+        const GeometrySet &geometry_set = reference.geometry_set();
+        if (!instances_attribute_foreach_recursive(geometry_set, callback, limit, count)) {
+          return false;
+        }
+        break;
+      }
       case InstanceReference::Type::None: {
         break;
       }
diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 062264c5729..bca1afbf101 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -1979,8 +1979,7 @@ int BKE_object_visibility(const Object *ob, const int dag_eval_mode)
     visibility |= OB_VISIBLE_INSTANCES;
   }
 
-  if (ob->runtime.geometry_set_eval != NULL &&
-      BKE_geometry_set_has_instances(ob->runtime.geometry_set_eval)) {
+  if (BKE_object_has_geometry_set_instances(ob)) {
     visibility |= OB_VISIBLE_INSTANCES;
   }
 
@@ -5737,3 +5736,13 @@ void BKE_object_modifiers_lib_link_common(void *userData,
     id_us_plus_no_lib(*idpoin);
   }
 }
+
+void BKE_object_replace_data_on_shallow_copy(Object *ob, ID *new_data)
+{
+  ob->type = BKE_object_obdata_to_type(new_data);
+  ob->data = new_data;
+  ob->runtime.geometry_set_eval = NULL;
+  ob->runtime.data_eval = NULL;
+  ob->runtime.bb->flag |= BOUNDBOX_DIRTY;
+  ob->id.py_instance = NULL;
+}
diff --git a/source/blender/blenkernel/intern/object_dupli.cc b/source/blender/blenkernel/intern/object_dupli.cc
index a46ac4b1175..47d4d03d1e1 100644
--- a/source/blender/blenkernel/intern/object_dupli.cc
+++ b/source/blender/blenkernel/intern/object_dupli.cc
@@ -194,6 +194,7 @@ static DupliObject *make_dupli(const DupliContext *ctx,
   }
 
   dob->ob = ob;
+  dob->ob_data = (ID *)ob->data;
   mul_m4_m4m4(dob->mat, (float(*)[4])ctx->space_mat, mat);
   dob->type = ctx->gen->type;
 
@@ -834,14 +835,59 @@ static const DupliGenerator gen_dupli_verts_pointcloud = {
 /** \name Instances Geometry Component Implementation
  * \{ */
 
-static void make_duplis_instances_component(const DupliContext *ctx)
+static void make_duplis_geometry_set_impl(const DupliContext *ctx,
+                                          const GeometrySet &geometry_set,
+                                          const float parent_transform[4][4],
+                                          bool geometry_set_is_instance)
 {
-  const InstancesComponent *component =
-      ctx->object->runtime.geometry_set_eval->get_component_for_read<InstancesComponent>();
+  int component_index = 0;
+  if (ctx->object->type != OB_MESH || geometry_set_is_instance) {
+    const Mesh *mesh = geometry_set.get_mesh_for_read();
+    if (mesh != nullptr) {
+      DupliObject *dupli = make_dupli(ctx, ctx->object, parent_transform, component_index++);
+      dupli->ob_data = (ID *)mesh;
+    }
+  }
+  if (ctx->object->type != OB_VOLUME || geometry_set_is_instance) {
+    const Volume *volume = geometry_set.get_volume_for_read();
+    if (volume != nullptr) {
+      DupliObject *dupli = make_dupli(ctx, ctx->object, parent_transform, component_index++);
+      dupli->ob_data = (ID *)volume;
+    }
+  }
+  if (ctx->object->type != OB_CURVE || geometry_set_is_instance) {
+    const CurveComponent *curve_component = geometry_set.get_component_for_read<CurveComponent>();
+    if (curve_component != nullptr) {
+      const Curve *curve = curve_component->get_curve_for_render();
+      if (curve != nullptr) {
+        DupliObject *dupli = make_dupli(ctx, ctx->object, parent_transform, component_index++);
+        dupli->ob_data = (ID *)curve;
+      }
+    }
+  }
+  if (ctx->object->type != OB_POINTCLOUD || geometry_set_is_instance) {
+    const PointCloud *pointcloud = geometry_set.get_pointcloud_for_read();
+    if (pointcloud != nullptr) {
+      DupliObject *dupli = make_dupli(ctx, ctx->object, parent_transform, component_index++);
+      dupli->ob_data = (ID *)pointcloud;
+    }
+  }
+  const bool creates_duplis_for_components = component_index >= 1;
+
+  const InstancesComponent *component = geometry_set.get_component_for_read<InstancesComponent>();
   if (component == nullptr) {
     return;
   }
 
+  const DupliContext *instances_ctx = ctx;
+  /* Create a sub-context if some duplis were created above. This is to avoid dupli id collisions
+   * between the instances component below and the other components above. */
+  DupliContext new_instances_ctx;
+  if (creates_duplis_for_components) {
+    copy_dupli_context(&new_instances_ctx, ctx, ctx->object, nullptr, component_index);
+    instances_ctx = &new_instances_ctx;
+  }
+
   Span<float4x4> instance_offset_matrices = component->instance_transforms();
   Span<int> instance_reference_handles = component->instance_reference_handles();
   Span<int> almost_unique_ids = component->almost_unique_ids();
@@ -855,13 +901,13 @@ static void make_duplis_instances_component(const DupliContext *ctx)
       case InstanceReference::Type::Object: {
         Object &object = reference.object();
         float matrix[4][4];
-        mul_m4_m4m4(matrix, ctx->object->obmat, instance_offset_matrices[i].values);
-        make_dupli(ctx, &object, matrix, id);
+        mul_m4_m4m4(matrix, parent_transform, instance_offset_matrices[i].values);
+        make_dupli(instances_ctx, &object, matrix, id);
 
         float space_matrix[4][4];
         mul_m4_m4m4(space_matrix, instance_offset_matrices[i].values, object.imat);
-        mul_m4_m4_pre(space_matrix, ctx->object->obmat);
-        make_recursive_duplis(ctx, &object, space_matrix, id);
+        mul_m4_m4_pre(space_matrix, parent_transform);
+        make_recursive_duplis(instances_ctx, &object, space_matrix, id);
         break;
       }
       case InstanceReference::Type::Collection: {
@@ -870,23 +916,36 @@ static void make_duplis_instances_component(const DupliContext *ctx)
         unit_m4(collection_matrix);
         sub_v3_v3(collection_matrix[3], collection.instance_offset);
         mul_m4_m4_pre(collection_matrix, instance_offset_matrices[i].values);
-        mul_m4_m4_pre(collection_matrix, ctx->object->obmat);
+        mul_m4_m4_pre(collection_matrix, parent_transform);
+
+        DupliContext sub_ctx;
+        copy_dupli_context(&sub_ctx, instances_ctx, instances_ctx->object, nullptr, id);
 
-        eEvaluationMode mode = DEG_get_mode(ctx->depsgraph);
+        eEvaluationMode mode = DEG_get_mode(instances_ctx->depsgraph);
+        int object_id = 0;
         FOREACH_COLLECTION_VISIBLE_OBJECT_RECURSIVE_BEGIN (&collection, object, mode) {
-          if (object == ctx->object) {
+          if (object == instances_ctx->object) {
             continue;
           }
 
           float instance_matrix[4][4];
           mul_m4_m4m4(instance_matrix, collection_matrix, object->obmat);
 
-          make_dupli(ctx, object, instance_matrix, id);
-          make_recursive_duplis(ctx, object, collection_matrix, id);
+          make_dupli(&sub_ctx, object, instance_matrix, object_id++);
+          make_recursive_duplis(&sub_ctx, object, collection_matrix, object_id++);
         }
         FOREACH_COLLECTION_VISIBLE_OBJECT_RECURSIVE_END;
         break;
       }
+      case InstanceReference::Type::GeometrySet: {
+        float new_transform[4][4];
+        mul_m4_m4m4(new_transform, parent_transform, instance_offset_matrices[i].values);
+
+        DupliContext sub_ctx;
+        copy_dupli_context(&sub_ctx, instances_ctx, instances_ctx->object, nullptr, id);
+        make_duplis_geometry_set_impl(&sub_ctx, reference.geometry_set(), new_transform, true);
+        break;
+      }
       case InstanceReference::Type::None: {
         break;
       }
@@ -894,9 +953,15 @@ static void make_duplis_instances_component(const DupliContext *ctx)
   }
 }
 
-static const DupliGenerator gen_dupli_instances_component = {
+static void make_duplis_geometry_set(const DupliContext *ctx)
+{
+  const GeometrySet *geometry_set = ctx->object->runtime.geometry_set_eval;
+  make_duplis_geometry_set_impl(ctx, *geometry_set, ctx->object->obmat, false);
+}
+
+static const DupliGenerator gen_dupli_geometry_set = {
     0,
-    make_duplis_instances_component,
+    make_duplis_geometry_set,
 };
 
 /** \} */
@@ -1567,8 +1632,8 @@ static const DupliGenerator *get_dupli_generator(const DupliContext *ctx)
   }
 
   if (ctx->object->runtime.geometry_set_eval != nullptr) {
-    if (BKE_geometry_set_has_instances(ctx->object->runtime.geometry_set_eval)) {
-      return &gen_dupli_instances_component;
+    if (BKE_object_has_geometry_set_instances(ctx->object)) {
+      return &gen_dupli_geometry_set;
     }
   }