Python: Expose crazyspace correction functionality via RNA

Allows to perform correction of coordinate delta/displacement in a
similar way of how sculpt mode handles sculpting on a deformed mesh.
An example of usecase of this is allowing riggers and sciprters to
improve corrective shapekey workflow.

The usage consists of pre-processing and access. For example:

  object.crazyspace_eval(depsgraph, scene)

  # When we have a difference between two vertices and want to convert
  # it to a space to be stored, say, in shapekey:
  delta_in_orig_space = rigged_ob.crazyspace_displacement_to_original(
      vertex_index=i, displacement=delta)

  # The reverse of above.
  delta_in_deformed_space = rigged_ob.crazyspace_displacement_to_deformed(
      vertex_index=i, displacement=delta)

  object.crazyspace_eval_clear()

Fuller explanation with actual usecases and studio examples are written in
the comment:

  https://developer.blender.org/D13892#368898

Differential Revision: https://developer.blender.org/D13892

source/blender/blenkernel/BKE_crazyspace.h

@@ -26,10 +26,12 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+
 struct BMEditMesh;
 struct Depsgraph;
 struct Mesh;
 struct Object;
+struct ReportList;
 struct Scene;
 
 /* crazyspace.c */
@@ -69,6 +71,31 @@ void BKE_crazyspace_build_sculpt(struct Depsgraph *depsgraph,
                                  float (**deformmats)[3][3],
                                  float (**deformcos)[3]);
 
+/* -------------------------------------------------------------------- */
+/** \name Crazyspace API
+ * \{ */
+
+void BKE_crazyspace_api_eval(struct Depsgraph *depsgraph,
+                             struct Scene *scene,
+                             struct Object *object,
+                             struct ReportList *reports);
+
+void BKE_crazyspace_api_displacement_to_deformed(struct Object *object,
+                                                 struct ReportList *reports,
+                                                 int vertex_index,
+                                                 float displacement[3],
+                                                 float r_displacement_deformed[3]);
+
+void BKE_crazyspace_api_displacement_to_original(struct Object *object,
+                                                 struct ReportList *reports,
+                                                 int vertex_index,
+                                                 float displacement_deformed[3],
+                                                 float r_displacement[3]);
+
+void BKE_crazyspace_api_eval_clear(struct Object *object);
+
+/** \} */
+
 #ifdef __cplusplus
 }
 #endif

source/blender/blenkernel/intern/crazyspace.c

@@ -41,6 +41,7 @@
 #include "BKE_mesh_wrapper.h"
 #include "BKE_modifier.h"
 #include "BKE_multires.h"
+#include "BKE_report.h"
 
 #include "DEG_depsgraph_query.h"
 
@@ -516,3 +517,85 @@ void BKE_crazyspace_build_sculpt(struct Depsgraph *depsgraph,
     }
   }
 }
+
+/* -------------------------------------------------------------------- */
+/** \name Crazyspace API
+ * \{ */
+
+void BKE_crazyspace_api_eval(Depsgraph *depsgraph,
+                             Scene *scene,
+                             Object *object,
+                             struct ReportList *reports)
+{
+  if (object->runtime.crazyspace_deform_imats != NULL ||
+      object->runtime.crazyspace_deform_cos != NULL) {
+    return;
+  }
+
+  if (object->type != OB_MESH) {
+    BKE_report(reports,
+               RPT_ERROR,
+               "Crazyspace transformation is only available for Mesh type of objects");
+    return;
+  }
+
+  const Mesh *mesh = (const Mesh *)object->data;
+  object->runtime.crazyspace_num_verts = mesh->totvert;
+  BKE_crazyspace_build_sculpt(depsgraph,
+                              scene,
+                              object,
+                              &object->runtime.crazyspace_deform_imats,
+                              &object->runtime.crazyspace_deform_cos);
+}
+
+void BKE_crazyspace_api_displacement_to_deformed(struct Object *object,
+                                                 struct ReportList *reports,
+                                                 int vertex_index,
+                                                 float displacement[3],
+                                                 float r_displacement_deformed[3])
+{
+  if (vertex_index < 0 || vertex_index >= object->runtime.crazyspace_num_verts) {
+    BKE_reportf(reports,
+                RPT_ERROR,
+                "Invalid vertex index %d (expected to be within 0 to %d range)",
+                vertex_index,
+                object->runtime.crazyspace_num_verts);
+    return;
+  }
+
+  mul_v3_m3v3(r_displacement_deformed,
+              object->runtime.crazyspace_deform_imats[vertex_index],
+              displacement);
+}
+
+void BKE_crazyspace_api_displacement_to_original(struct Object *object,
+                                                 struct ReportList *reports,
+                                                 int vertex_index,
+                                                 float displacement_deformed[3],
+                                                 float r_displacement[3])
+{
+  if (vertex_index < 0 || vertex_index >= object->runtime.crazyspace_num_verts) {
+    BKE_reportf(reports,
+                RPT_ERROR,
+                "Invalid vertex index %d (expected to be within 0 to %d range))",
+                vertex_index,
+                object->runtime.crazyspace_num_verts);
+    return;
+  }
+
+  float mat[3][3];
+  if (!invert_m3_m3(mat, object->runtime.crazyspace_deform_imats[vertex_index])) {
+    copy_v3_v3(r_displacement, displacement_deformed);
+    return;
+  }
+
+  mul_v3_m3v3(r_displacement, mat, displacement_deformed);
+}
+
+void BKE_crazyspace_api_eval_clear(Object *object)
+{
+  MEM_SAFE_FREE(object->runtime.crazyspace_deform_imats);
+  MEM_SAFE_FREE(object->runtime.crazyspace_deform_cos);
+}
+
+/** \} */

source/blender/blenkernel/intern/object.cc

@@ -87,6 +87,7 @@
 #include "BKE_camera.h"
 #include "BKE_collection.h"
 #include "BKE_constraint.h"
+#include "BKE_crazyspace.h"
 #include "BKE_curve.h"
 #include "BKE_deform.h"
 #include "BKE_displist.h"
@@ -1881,6 +1882,8 @@ void BKE_object_free_derived_caches(Object *ob)
   BKE_object_to_curve_clear(ob);
   BKE_object_free_curve_cache(ob);
 
+  BKE_crazyspace_api_eval_clear(ob);
+
   /* Clear grease pencil data. */
   if (ob->runtime.gpd_eval != nullptr) {
     BKE_gpencil_eval_delete(ob->runtime.gpd_eval);
@@ -5219,6 +5222,9 @@ void BKE_object_runtime_reset_on_copy(Object *object, const int UNUSED(flag))
   runtime->object_as_temp_mesh = nullptr;
   runtime->object_as_temp_curve = nullptr;
   runtime->geometry_set_eval = nullptr;
+
+  runtime->crazyspace_deform_imats = nullptr;
+  runtime->crazyspace_deform_cos = nullptr;
 }
 
 void BKE_object_runtime_free_data(Object *object)

source/blender/editors/object/object_shapekey.c

@@ -43,13 +43,16 @@
 #include "DNA_object_types.h"
 
 #include "BKE_context.h"
+#include "BKE_crazyspace.h"
 #include "BKE_key.h"
 #include "BKE_lattice.h"
 #include "BKE_main.h"
 #include "BKE_object.h"
+#include "BKE_report.h"
 
 #include "DEG_depsgraph.h"
 #include "DEG_depsgraph_build.h"
+#include "DEG_depsgraph_query.h"
 
 #include "BLI_sys_types.h" /* for intptr_t support */
 

source/blender/makesdna/DNA_object_types.h

@@ -216,6 +216,12 @@ typedef struct Object_Runtime {
 
   unsigned short local_collections_bits;
   short _pad2[3];
+
+  float (*crazyspace_deform_imats)[3][3];
+  float (*crazyspace_deform_cos)[3];
+  int crazyspace_num_verts;
+
+  int _pad3[3];
 } Object_Runtime;
 
 typedef struct ObjectLineArt {

source/blender/makesrna/intern/rna_object_api.c

@@ -68,6 +68,7 @@ static const EnumPropertyItem space_items[] = {
 #  include "BKE_bvhutils.h"
 #  include "BKE_constraint.h"
 #  include "BKE_context.h"
+#  include "BKE_crazyspace.h"
 #  include "BKE_customdata.h"
 #  include "BKE_global.h"
 #  include "BKE_layer.h"
@@ -379,6 +380,39 @@ static void rna_Object_camera_fit_coords(
       depsgraph, (const float(*)[3])cos, num_cos / 3, ob, co_ret, scale_ret);
 }
 
+static void rna_Object_crazyspace_eval(Object *object,
+                                       ReportList *reports,
+                                       Depsgraph *depsgraph,
+                                       Scene *scene)
+{
+  BKE_crazyspace_api_eval(depsgraph, scene, object, reports);
+}
+
+static void rna_Object_crazyspace_displacement_to_deformed(Object *object,
+                                                           ReportList *reports,
+                                                           const int vertex_index,
+                                                           float displacement[3],
+                                                           float r_displacement_deformed[3])
+{
+  BKE_crazyspace_api_displacement_to_deformed(
+      object, reports, vertex_index, displacement, r_displacement_deformed);
+}
+
+static void rna_Object_crazyspace_displacement_to_original(Object *object,
+                                                           ReportList *reports,
+                                                           const int vertex_index,
+                                                           float displacement_deformed[3],
+                                                           float r_displacement[3])
+{
+  BKE_crazyspace_api_displacement_to_original(
+      object, reports, vertex_index, displacement_deformed, r_displacement);
+}
+
+static void rna_Object_crazyspace_eval_clear(Object *object)
+{
+  BKE_crazyspace_api_eval_clear(object);
+}
+
 /* copied from Mesh_getFromObject and adapted to RNA interface */
 static Mesh *rna_Object_to_mesh(Object *object,
                                 ReportList *reports,
@@ -978,6 +1012,52 @@ void RNA_api_object(StructRNA *srna)
       parm, "", "The ortho scale to aim to be able to see all given points (if relevant)");
   RNA_def_parameter_flags(parm, 0, PARM_OUTPUT);
 
+  /* Crazyspace access. */
+
+  func = RNA_def_function(srna, "crazyspace_eval", "rna_Object_crazyspace_eval");
+  RNA_def_function_ui_description(
+      func,
+      "Compute orientation mapping between vertices of an original object and object with shape "
+      "keys and deforming modifiers applied."
+      "The evaluation is to be freed with the crazyspace_eval_free function");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS);
+  parm = RNA_def_pointer(
+      func, "depsgraph", "Depsgraph", "Dependency Graph", "Evaluated dependency graph");
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
+  parm = RNA_def_pointer(func, "scene", "Scene", "Scene", "Scene of the object");
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
+
+  func = RNA_def_function(srna,
+                          "crazyspace_displacement_to_deformed",
+                          "rna_Object_crazyspace_displacement_to_deformed");
+  RNA_def_function_ui_description(
+      func, "Convert displacement vector from non-deformed object space to deformed object space");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS);
+  RNA_def_property(func, "vertex_index", PROP_INT, PROP_NONE);
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
+  parm = RNA_def_property(func, "displacement", PROP_FLOAT, PROP_XYZ);
+  RNA_def_property_array(parm, 3);
+  parm = RNA_def_property(func, "displacement_deformed", PROP_FLOAT, PROP_XYZ);
+  RNA_def_property_array(parm, 3);
+  RNA_def_function_output(func, parm);
+
+  func = RNA_def_function(srna,
+                          "crazyspace_displacement_to_original",
+                          "rna_Object_crazyspace_displacement_to_original");
+  RNA_def_function_ui_description(
+      func, "Convert displacement vector from deformed object space to non-deformed object space");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS);
+  RNA_def_property(func, "vertex_index", PROP_INT, PROP_NONE);
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
+  parm = RNA_def_property(func, "displacement", PROP_FLOAT, PROP_XYZ);
+  RNA_def_property_array(parm, 3);
+  parm = RNA_def_property(func, "displacement_original", PROP_FLOAT, PROP_XYZ);
+  RNA_def_property_array(parm, 3);
+  RNA_def_function_output(func, parm);
+
+  RNA_def_function(srna, "crazyspace_eval_clear", "rna_Object_crazyspace_eval_clear");
+  RNA_def_function_ui_description(func, "Free evaluated state of crazyspace");
+
   /* mesh */
   func = RNA_def_function(srna, "to_mesh", "rna_Object_to_mesh");
   RNA_def_function_ui_description(