Multires: Fix Subdivide, Reshape and Apply Base

This change fixes artifacts produced by these operations.

On a technical aspect this is done by porting all of the operations
to the new subdivision surface implementation which ensures that
tangent space used to evaluate modifier and those operations is
exactly the same (before modifier will use new code and the operations
will still use an old one).

The next step is to get sculpting on a non-top level to work, and
that actually requires fixes in the undo system.

1 files changed, 233 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/multires_reshape.c b/source/blender/blenkernel/intern/multires_reshape.c
new file mode 100644
index 00000000000..82f6e70692b
--- /dev/null
+++ b/source/blender/blenkernel/intern/multires_reshape.c
@@ -0,0 +1,233 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software  Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2020 Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include "MEM_guardedalloc.h"
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+#include "DNA_modifier_types.h"
+#include "DNA_scene_types.h"
+
+#include "BLI_math_vector.h"
+
+#include "BKE_customdata.h"
+#include "BKE_lib_id.h"
+#include "BKE_mesh.h"
+#include "BKE_mesh_runtime.h"
+#include "BKE_modifier.h"
+#include "BKE_multires.h"
+#include "BKE_subdiv.h"
+
+#include "DEG_depsgraph_query.h"
+
+#include "multires_reshape.h"
+
+/* ================================================================================================
+ * Reshape from object.
+ */
+
+bool multiresModifier_reshapeFromVertcos(struct Depsgraph *depsgraph,
+                                         struct Object *object,
+                                         struct MultiresModifierData *mmd,
+                                         const float (*vert_coords)[3],
+                                         const int num_vert_coords)
+{
+  MultiresReshapeContext reshape_context;
+  if (!multires_reshape_context_create_from_object(&reshape_context, depsgraph, object, mmd)) {
+    return false;
+  }
+  multires_reshape_store_original_grids(&reshape_context);
+  multires_reshape_ensure_grids(object->data, reshape_context.top.level);
+  if (!multires_reshape_assign_final_coords_from_vertcos(
+          &reshape_context, vert_coords, num_vert_coords)) {
+    multires_reshape_context_free(&reshape_context);
+    return false;
+  }
+  multires_reshape_smooth_object_grids_with_details(&reshape_context);
+  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
+  multires_reshape_context_free(&reshape_context);
+  return true;
+}
+
+/* Returns truth on success, false otherwise.
+ *
+ * This function might fail in cases like source and destination not having
+ * matched amount of vertices. */
+bool multiresModifier_reshapeFromObject(struct Depsgraph *depsgraph,
+                                        struct MultiresModifierData *mmd,
+                                        struct Object *dst,
+                                        struct Object *src)
+{
+  struct Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
+  struct Object *src_eval = DEG_get_evaluated_object(depsgraph, src);
+  Mesh *src_mesh_eval = mesh_get_eval_final(depsgraph, scene_eval, src_eval, &CD_MASK_BAREMESH);
+
+  int num_deformed_verts;
+  float(*deformed_verts)[3] = BKE_mesh_vert_coords_alloc(src_mesh_eval, &num_deformed_verts);
+
+  const bool result = multiresModifier_reshapeFromVertcos(
+      depsgraph, dst, mmd, deformed_verts, num_deformed_verts);
+
+  MEM_freeN(deformed_verts);
+
+  return result;
+}
+
+/* ================================================================================================
+ * Reshape from modifier.
+ */
+
+bool multiresModifier_reshapeFromDeformModifier(struct Depsgraph *depsgraph,
+                                                struct Object *object,
+                                                struct MultiresModifierData *mmd,
+                                                struct ModifierData *deform_md)
+{
+  MultiresModifierData highest_mmd = *mmd;
+  highest_mmd.sculptlvl = highest_mmd.totlvl;
+  highest_mmd.lvl = highest_mmd.totlvl;
+  highest_mmd.renderlvl = highest_mmd.totlvl;
+
+  Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
+
+  /* Create mesh for the multires, ignoring any further modifiers (leading
+   * deformation modifiers will be applied though). */
+  Mesh *multires_mesh = BKE_multires_create_mesh(depsgraph, scene_eval, &highest_mmd, object);
+  int num_deformed_verts;
+  float(*deformed_verts)[3] = BKE_mesh_vert_coords_alloc(multires_mesh, &num_deformed_verts);
+
+  /* Apply deformation modifier on the multires, */
+  const ModifierEvalContext modifier_ctx = {
+      .depsgraph = depsgraph,
+      .object = object,
+      .flag = MOD_APPLY_USECACHE | MOD_APPLY_IGNORE_SIMPLIFY,
+  };
+  modwrap_deformVerts(
+      deform_md, &modifier_ctx, multires_mesh, deformed_verts, multires_mesh->totvert);
+  BKE_id_free(NULL, multires_mesh);
+
+  /* Reshaping */
+  bool result = multiresModifier_reshapeFromVertcos(
+      depsgraph, object, &highest_mmd, deformed_verts, num_deformed_verts);
+
+  /* Cleanup */
+  MEM_freeN(deformed_verts);
+
+  return result;
+}
+
+/* ================================================================================================
+ * Reshape from grids.
+ */
+
+bool multiresModifier_reshapeFromCCG(const int tot_level,
+                                     Mesh *coarse_mesh,
+                                     struct SubdivCCG *subdiv_ccg)
+{
+  MultiresReshapeContext reshape_context;
+  if (!multires_reshape_context_create_from_ccg(
+          &reshape_context, subdiv_ccg, coarse_mesh, tot_level)) {
+    return false;
+  }
+  multires_reshape_store_original_grids(&reshape_context);
+  multires_reshape_ensure_grids(coarse_mesh, reshape_context.top.level);
+  if (!multires_reshape_assign_final_coords_from_ccg(&reshape_context, subdiv_ccg)) {
+    multires_reshape_context_free(&reshape_context);
+    return false;
+  }
+  multires_reshape_smooth_object_grids_with_details(&reshape_context);
+  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
+  multires_reshape_context_free(&reshape_context);
+  return true;
+}
+
+/* ================================================================================================
+ * Subdivision.
+ */
+
+void multiresModifier_subdivide(Object *object, MultiresModifierData *mmd)
+{
+  const int top_level = mmd->totlvl + 1;
+  multiresModifier_subdivide_to_level(object, mmd, top_level);
+}
+
+void multiresModifier_subdivide_to_level(struct Object *object,
+                                         struct MultiresModifierData *mmd,
+                                         const int top_level)
+{
+  if (top_level <= mmd->totlvl) {
+    return;
+  }
+
+  Mesh *coarse_mesh = object->data;
+  MultiresReshapeContext reshape_context;
+
+  /* There was no multires at all, all displacement is at 0. Can simply make sure all mdisps grids
+   * are allocated at a proper level and return. */
+  const bool has_mdisps = CustomData_has_layer(&coarse_mesh->ldata, CD_MDISPS);
+  if (!has_mdisps) {
+    CustomData_add_layer(&coarse_mesh->ldata, CD_MDISPS, CD_CALLOC, NULL, coarse_mesh->totloop);
+  }
+  if (!has_mdisps || top_level == 1) {
+    multires_reshape_ensure_grids(coarse_mesh, top_level);
+    multires_set_tot_level(object, mmd, top_level);
+    return;
+  }
+
+  multires_flush_sculpt_updates(object);
+
+  if (!multires_reshape_context_create_from_subdivide(&reshape_context, object, mmd, top_level)) {
+    return;
+  }
+  multires_reshape_store_original_grids(&reshape_context);
+  multires_reshape_ensure_grids(coarse_mesh, reshape_context.top.level);
+  multires_reshape_assign_final_coords_from_orig_mdisps(&reshape_context);
+  multires_reshape_smooth_object_grids(&reshape_context);
+  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
+  multires_reshape_context_free(&reshape_context);
+
+  multires_set_tot_level(object, mmd, top_level);
+}
+
+/* ================================================================================================
+ * Apply base.
+ */
+
+void multiresModifier_base_apply(struct Depsgraph *depsgraph,
+                                 Object *object,
+                                 MultiresModifierData *mmd)
+{
+  multires_force_sculpt_rebuild(object);
+
+  MultiresReshapeContext reshape_context;
+  if (!multires_reshape_context_create_from_object(&reshape_context, depsgraph, object, mmd)) {
+    return;
+  }
+
+  multires_reshape_assign_final_coords_from_mdisps(&reshape_context);
+  multires_reshape_apply_base_update_mesh_coords(&reshape_context);
+  multires_reshape_apply_base_refit_base_mesh(&reshape_context);
+  multires_reshape_apply_base_refine_subdiv(&reshape_context);
+  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
+
+  multires_reshape_context_free(&reshape_context);
+}