Alembic import: option to always add a cache reader

The current behavior of the Alembic importer is to only create a
`MeshSequenceCache` modifier or a `Transform Cache` constraint to imported
objects if they have some animated properties.

Since static objects do not have a cache reader, when reloading files those
objects are not updated. Currently, the only way to properly reload a file
because of this is to reimport it.

This adds an option to the importer to always add a cache reader, even if
there is no animated data, to ensure that all objects coming from Alembic
archive are linked to them and updated properly upon reloads.

Reviewed by: brecht, sybren

Ref D10197.

8 files changed, 20 insertions, 5 deletions

diff --git a/source/blender/editors/io/io_alembic.c b/source/blender/editors/io/io_alembic.c
index 12890552b1d..bbff37221e8 100644
--- a/source/blender/editors/io/io_alembic.c
+++ b/source/blender/editors/io/io_alembic.c
@@ -615,6 +615,7 @@ static void ui_alembic_import_settings(uiLayout *layout, PointerRNA *imfptr)
   uiItemR(col, imfptr, "set_frame_range", 0, NULL, ICON_NONE);
   uiItemR(col, imfptr, "is_sequence", 0, NULL, ICON_NONE);
   uiItemR(col, imfptr, "validate_meshes", 0, NULL, ICON_NONE);
+  uiItemR(col, imfptr, "always_add_cache_reader", 0, NULL, ICON_NONE);
 }
 
 static void wm_alembic_import_draw(bContext *UNUSED(C), wmOperator *op)
@@ -645,6 +646,7 @@ static int wm_alembic_import_exec(bContext *C, wmOperator *op)
   const bool is_sequence = RNA_boolean_get(op->ptr, "is_sequence");
   const bool set_frame_range = RNA_boolean_get(op->ptr, "set_frame_range");
   const bool validate_meshes = RNA_boolean_get(op->ptr, "validate_meshes");
+  const bool always_add_cache_reader = RNA_boolean_get(op->ptr, "always_add_cache_reader");
   const bool as_background_job = RNA_boolean_get(op->ptr, "as_background_job");
 
   int offset = 0;
@@ -672,6 +674,7 @@ static int wm_alembic_import_exec(bContext *C, wmOperator *op)
                        sequence_len,
                        offset,
                        validate_meshes,
+                       always_add_cache_reader,
                        as_background_job);
 
   return as_background_job || ok ? OPERATOR_FINISHED : OPERATOR_CANCELLED;
@@ -722,6 +725,13 @@ void WM_OT_alembic_import(wmOperatorType *ot)
                   "Check imported mesh objects for invalid data (slow)");
 
   RNA_def_boolean(ot->srna,
+                  "always_add_cache_reader",
+                  false,
+                  "Always Add Cache Reader",
+                  "Add cache modifiers and constraints to imported objects even if they are not "
+                  "animated so that they can be updated when reloading the Alembic archive");
+
+  RNA_def_boolean(ot->srna,
                   "is_sequence",
                   false,
                   "Is Sequence",
diff --git a/source/blender/io/alembic/ABC_alembic.h b/source/blender/io/alembic/ABC_alembic.h
index 0dbebb1e4c4..0a3a43bb21f 100644
--- a/source/blender/io/alembic/ABC_alembic.h
+++ b/source/blender/io/alembic/ABC_alembic.h
@@ -97,6 +97,7 @@ bool ABC_import(struct bContext *C,
                 int sequence_len,
                 int offset,
                 bool validate_meshes,
+                bool always_add_cache_reader,
                 bool as_background_job);
 
 struct CacheArchiveHandle *ABC_create_handle(struct Main *bmain,
diff --git a/source/blender/io/alembic/intern/abc_reader_curves.cc b/source/blender/io/alembic/intern/abc_reader_curves.cc
index 8d6605d6973..27ee35d1b39 100644
--- a/source/blender/io/alembic/intern/abc_reader_curves.cc
+++ b/source/blender/io/alembic/intern/abc_reader_curves.cc
@@ -112,7 +112,7 @@ void AbcCurveReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSele
 
   read_curve_sample(cu, m_curves_schema, sample_sel);
 
-  if (has_animations(m_curves_schema, m_settings)) {
+  if (m_settings->always_add_cache_reader || has_animations(m_curves_schema, m_settings)) {
     addCacheModifier();
   }
 }
diff --git a/source/blender/io/alembic/intern/abc_reader_mesh.cc b/source/blender/io/alembic/intern/abc_reader_mesh.cc
index c05df7f1ff5..77edd4908bd 100644
--- a/source/blender/io/alembic/intern/abc_reader_mesh.cc
+++ b/source/blender/io/alembic/intern/abc_reader_mesh.cc
@@ -578,7 +578,7 @@ void AbcMeshReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
 
   readFaceSetsSample(bmain, mesh, sample_sel);
 
-  if (has_animations(m_schema, m_settings)) {
+  if (m_settings->always_add_cache_reader || has_animations(m_schema, m_settings)) {
     addCacheModifier();
   }
 }
@@ -928,7 +928,7 @@ void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
     BKE_mesh_validate(mesh, false, false);
   }
 
-  if (has_animations(m_schema, m_settings)) {
+  if (m_settings->always_add_cache_reader || has_animations(m_schema, m_settings)) {
     addCacheModifier();
   }
 }
diff --git a/source/blender/io/alembic/intern/abc_reader_object.cc b/source/blender/io/alembic/intern/abc_reader_object.cc
index d136d8c3e91..9a5ffd04bd1 100644
--- a/source/blender/io/alembic/intern/abc_reader_object.cc
+++ b/source/blender/io/alembic/intern/abc_reader_object.cc
@@ -197,7 +197,7 @@ void AbcObjectReader::setupObjectTransform(const float time)
   BKE_object_apply_mat4(m_object, transform_from_alembic, true, false);
   BKE_object_to_mat4(m_object, m_object->obmat);
 
-  if (!is_constant) {
+  if (!is_constant || m_settings->always_add_cache_reader) {
     bConstraint *con = BKE_constraint_add_for_object(
         m_object, nullptr, CONSTRAINT_TYPE_TRANSFORM_CACHE);
     bTransformCacheConstraint *data = static_cast<bTransformCacheConstraint *>(con->data);
diff --git a/source/blender/io/alembic/intern/abc_reader_object.h b/source/blender/io/alembic/intern/abc_reader_object.h
index dacdcf3f722..89590b26b61 100644
--- a/source/blender/io/alembic/intern/abc_reader_object.h
+++ b/source/blender/io/alembic/intern/abc_reader_object.h
@@ -51,6 +51,7 @@ struct ImportSettings {
   int read_flag;
 
   bool validate_meshes;
+  bool always_add_cache_reader;
 
   CacheFile *cache_file;
 
@@ -65,6 +66,7 @@ struct ImportSettings {
         sequence_offset(0),
         read_flag(0),
         validate_meshes(false),
+        always_add_cache_reader(false),
         cache_file(NULL)
   {
   }
diff --git a/source/blender/io/alembic/intern/abc_reader_points.cc b/source/blender/io/alembic/intern/abc_reader_points.cc
index f7dcba7a0de..3aeacbd14fe 100644
--- a/source/blender/io/alembic/intern/abc_reader_points.cc
+++ b/source/blender/io/alembic/intern/abc_reader_points.cc
@@ -95,7 +95,7 @@ void AbcPointsReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSel
   m_object = BKE_object_add_only_object(bmain, OB_MESH, m_object_name.c_str());
   m_object->data = mesh;
 
-  if (has_animations(m_schema, m_settings)) {
+  if (m_settings->always_add_cache_reader || has_animations(m_schema, m_settings)) {
     addCacheModifier();
   }
 }
diff --git a/source/blender/io/alembic/intern/alembic_capi.cc b/source/blender/io/alembic/intern/alembic_capi.cc
index b94b75b2216..deb945b767c 100644
--- a/source/blender/io/alembic/intern/alembic_capi.cc
+++ b/source/blender/io/alembic/intern/alembic_capi.cc
@@ -663,6 +663,7 @@ bool ABC_import(bContext *C,
                 int sequence_len,
                 int offset,
                 bool validate_meshes,
+                bool always_add_cache_reader,
                 bool as_background_job)
 {
   /* Using new here since MEM_* functions do not call constructor to properly initialize data. */
@@ -681,6 +682,7 @@ bool ABC_import(bContext *C,
   job->settings.sequence_len = sequence_len;
   job->settings.sequence_offset = offset;
   job->settings.validate_meshes = validate_meshes;
+  job->settings.always_add_cache_reader = always_add_cache_reader;
   job->error_code = ABC_NO_ERROR;
   job->was_cancelled = false;
   job->archive = nullptr;