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

1 files changed, 81 insertions, 16 deletions

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;
     }
   }