Multires: Subdivide Simple and Subdivide Linear

This introduces two alternative subdivision modes that generates
displacement on the grids that look as Simple subdivisions but while
using the Catmull-Clark subdivision type in the modifier. This way,
Simple and Catmull-Clark subdivision can be combined when creating new
levels if needed, for example, to sculpt hard surface objects.

Subdivide simple smooths the sculpted data when creating a new
subdivision level. Subdivide linear also preserves the sharpness
in the sculpted data.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D7415

release/scripts/startup/bl_ui/properties_data_modifier.py

@@ -696,7 +696,15 @@ class DATA_PT_modifiers(ModifierButtonsPanel, Panel):
         col = split.column()
 
         col.enabled = ob.mode != 'EDIT'
-        col.operator("object.multires_subdivide", text="Subdivide")
+        op = col.operator("object.multires_subdivide", text="Subdivide")
+        op.mode = 'CATMULL_CLARK'
+
+        op = col.operator("object.multires_subdivide", text="Subdivide Simple")
+        op.mode = 'SIMPLE'
+
+        op = col.operator("object.multires_subdivide", text="Subdivide Linear")
+        op.mode = 'LINEAR'
+
         col.operator("object.multires_higher_levels_delete", text="Delete Higher")
         col.operator("object.multires_unsubdivide", text="Unsubdivide")
         col.operator("object.multires_reshape", text="Reshape")

source/blender/blenkernel/BKE_multires.h

@@ -180,13 +180,25 @@ bool multiresModifier_reshapeFromCCG(const int tot_level,
                                      struct SubdivCCG *subdiv_ccg);
 
 /* Subdivide multires displacement once. */
-void multiresModifier_subdivide(struct Object *object, struct MultiresModifierData *mmd);
+
+typedef enum eMultiresSubdivideModeType {
+  MULTIRES_SUBDIVIDE_CATMULL_CLARK,
+  MULTIRES_SUBDIVIDE_SIMPLE,
+  MULTIRES_SUBDIVIDE_LINEAR,
+} eMultiresSubdivideModeType;
+
+void multiresModifier_subdivide(struct Object *object,
+                                struct MultiresModifierData *mmd,
+                                const eMultiresSubdivideModeType mode);
+void multires_subdivide_create_tangent_displacement_linear_grids(struct Object *object,
+                                                                 struct MultiresModifierData *mmd);
 
 /* Subdivide displacement to the given level.
  * If level is lower than the current top level nothing happens. */
 void multiresModifier_subdivide_to_level(struct Object *object,
                                          struct MultiresModifierData *mmd,
-                                         const int top_level);
+                                         const int top_level,
+                                         const eMultiresSubdivideModeType mode);
 
 /* Subdivision integration, defined in multires_subdiv.c */
 

source/blender/blenkernel/CMakeLists.txt

@@ -175,6 +175,7 @@ set(SRC
   intern/multires_reshape_apply_base.c
   intern/multires_reshape_ccg.c
   intern/multires_reshape_smooth.c
+  intern/multires_reshape_subdivide.c
   intern/multires_reshape_util.c
   intern/multires_reshape_vertcos.c
   intern/multires_subdiv.c

source/blender/blenkernel/intern/multires.c

@@ -2234,7 +2234,14 @@ void multiresModifier_sync_levels_ex(Object *ob_dst,
   }
 
   if (mmd_src->totlvl > mmd_dst->totlvl) {
-    multiresModifier_subdivide_to_level(ob_dst, mmd_dst, mmd_src->totlvl);
+    if (mmd_dst->simple) {
+      multiresModifier_subdivide_to_level(
+          ob_dst, mmd_dst, mmd_src->totlvl, MULTIRES_SUBDIVIDE_SIMPLE);
+    }
+    else {
+      multiresModifier_subdivide_to_level(
+          ob_dst, mmd_dst, mmd_src->totlvl, MULTIRES_SUBDIVIDE_CATMULL_CLARK);
+    }
   }
   else {
     multires_del_higher(mmd_dst, ob_dst, mmd_src->totlvl);

source/blender/blenkernel/intern/multires_reshape.c

@@ -28,8 +28,6 @@
 #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"
@@ -37,6 +35,8 @@
 #include "BKE_modifier.h"
 #include "BKE_multires.h"
 #include "BKE_subdiv.h"
+#include "BKE_subsurf.h"
+#include "BLI_math_vector.h"
 
 #include "DEG_depsgraph_query.h"
 
@@ -171,15 +171,18 @@ bool multiresModifier_reshapeFromCCG(const int tot_level,
 /** \name Subdivision
  * \{ */
 
-void multiresModifier_subdivide(Object *object, MultiresModifierData *mmd)
+void multiresModifier_subdivide(Object *object,
+                                MultiresModifierData *mmd,
+                                const eMultiresSubdivideModeType mode)
 {
   const int top_level = mmd->totlvl + 1;
-  multiresModifier_subdivide_to_level(object, mmd, top_level);
+  multiresModifier_subdivide_to_level(object, mmd, top_level, mode);
 }
 
 void multiresModifier_subdivide_to_level(struct Object *object,
                                          struct MultiresModifierData *mmd,
-                                         const int top_level)
+                                         const int top_level,
+                                         const eMultiresSubdivideModeType mode)
 {
   if (top_level <= mmd->totlvl) {
     return;
@@ -196,7 +199,12 @@ void multiresModifier_subdivide_to_level(struct Object *object,
   }
   if (!has_mdisps || top_level == 1) {
     multires_reshape_ensure_grids(coarse_mesh, top_level);
-    multires_set_tot_level(object, mmd, top_level);
+    if (ELEM(mode, MULTIRES_SUBDIVIDE_LINEAR, MULTIRES_SUBDIVIDE_SIMPLE)) {
+      multires_subdivide_create_tangent_displacement_linear_grids(object, mmd);
+    }
+    else {
+      multires_set_tot_level(object, mmd, top_level);
+    }
     return;
   }
 
@@ -205,16 +213,22 @@ void multiresModifier_subdivide_to_level(struct Object *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);
 
-  /* Free original grids which makes it so smoothing with details thinks all the details were
-   * added against base mesh's limit surface. This is similar behavior to as if we've done all
-   * displacement in sculpt mode at the old top level and then propagated to the new top level. */
-  multires_reshape_free_original_grids(&reshape_context);
+  if (ELEM(mode, MULTIRES_SUBDIVIDE_LINEAR, MULTIRES_SUBDIVIDE_SIMPLE)) {
+    multires_reshape_smooth_object_grids(&reshape_context, mode);
+  }
+  else {
+    /* Free original grids which makes it so smoothing with details thinks all the details were
+     * added against base mesh's limit surface. This is similar behavior to as if we've done all
+     * displacement in sculpt mode at the old top level and then propagated to the new top level.*/
+    multires_reshape_free_original_grids(&reshape_context);
 
-  multires_reshape_smooth_object_grids_with_details(&reshape_context);
+    multires_reshape_smooth_object_grids_with_details(&reshape_context);
+  }
   multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
   multires_reshape_context_free(&reshape_context);
 

source/blender/blenkernel/intern/multires_reshape.h

@@ -25,6 +25,7 @@
 #define __BKE_INTERN_MULTIRES_RESHAPE_H__
 
 #include "BLI_sys_types.h"
+#include "BKE_multires.h"
 
 struct Depsgraph;
 struct GridPaintMask;
@@ -289,7 +290,8 @@ void multires_reshape_smooth_object_grids_with_details(
  *
  * Makes it so surface on top level looks smooth. Details are not preserved
  */
-void multires_reshape_smooth_object_grids(const MultiresReshapeContext *reshape_context);
+void multires_reshape_smooth_object_grids(const MultiresReshapeContext *reshape_context,
+                                          const enum eMultiresSubdivideModeType mode);
 
 /* --------------------------------------------------------------------
  * Displacement, space conversion.
@@ -324,5 +326,4 @@ void multires_reshape_apply_base_refine_from_base(MultiresReshapeContext *reshap
  *
  * NOTE: Will re-evaluate all leading modifiers, so it's not cheap. */
 void multires_reshape_apply_base_refine_from_deform(MultiresReshapeContext *reshape_context);
-
 #endif /* __BKE_INTERN_MULTIRES_RESHAPE_H__ */

source/blender/blenkernel/intern/multires_reshape_smooth.c

@@ -119,6 +119,14 @@ typedef struct MultiresReshapeSmoothContext {
   Subdiv *reshape_subdiv;
 
   SurfaceGrid *base_surface_grids;
+
+  /* Defines how displacement is interpolated on the higher levels (for example, whether
+   * displacement is smoothed in Catmull-Clark mode or interpolated linearly preserving sharp edges
+   * of the current sculpt level).
+   *
+   * NOTE: Uses same enumerator type as Subdivide operator, since the values are the same and
+   * decoupling type just adds extra headache to convert one enumerator to another. */
+  eMultiresSubdivideModeType smoothing_type;
 } MultiresReshapeSmoothContext;
 
 /** \} */
@@ -412,15 +420,17 @@ static int get_reshape_level_resolution(const MultiresReshapeContext *reshape_co
 static char get_effective_edge_crease_char(
     const MultiresReshapeSmoothContext *reshape_smooth_context, const MEdge *base_edge)
 {
-  const MultiresReshapeContext *reshape_context = reshape_smooth_context->reshape_context;
-  if (reshape_context->subdiv->settings.is_simple) {
+  if (ELEM(reshape_smooth_context->smoothing_type,
+           MULTIRES_SUBDIVIDE_LINEAR,
+           MULTIRES_SUBDIVIDE_SIMPLE)) {
     return 255;
   }
   return base_edge->crease;
 }
 
 static void context_init(MultiresReshapeSmoothContext *reshape_smooth_context,
-                         const MultiresReshapeContext *reshape_context)
+                         const MultiresReshapeContext *reshape_context,
+                         const eMultiresSubdivideModeType mode)
 {
   reshape_smooth_context->reshape_context = reshape_context;
 
@@ -440,6 +450,8 @@ static void context_init(MultiresReshapeSmoothContext *reshape_smooth_context,
   reshape_smooth_context->non_loose_base_edge_map = NULL;
   reshape_smooth_context->reshape_subdiv = NULL;
   reshape_smooth_context->base_surface_grids = NULL;
+
+  reshape_smooth_context->smoothing_type = mode;
 }
 
 static void context_free_geometry(MultiresReshapeSmoothContext *reshape_smooth_context)
@@ -474,12 +486,14 @@ static void context_free(MultiresReshapeSmoothContext *reshape_smooth_context)
 
 static bool foreach_topology_info(const SubdivForeachContext *foreach_context,
                                   const int num_vertices,
-                                  const int UNUSED(num_edges),
+                                  const int num_edges,
                                   const int num_loops,
                                   const int num_polygons)
 {
   MultiresReshapeSmoothContext *reshape_smooth_context = foreach_context->user_data;
-  const int max_edges = reshape_smooth_context->geometry.max_edges;
+  const int max_edges = reshape_smooth_context->smoothing_type == MULTIRES_SUBDIVIDE_LINEAR ?
+                            num_edges :
+                            reshape_smooth_context->geometry.max_edges;
 
   /* NOTE: Calloc so the counters are re-set to 0 "for free". */
   reshape_smooth_context->geometry.num_vertices = num_vertices;
@@ -672,6 +686,22 @@ static void foreach_vertex_of_loose_edge(const struct SubdivForeachContext *fore
   }
 }
 
+static void store_edge(MultiresReshapeSmoothContext *reshape_smooth_context,
+                       const int subdiv_v1,
+                       const int subdiv_v2,
+                       const char crease)
+{
+  /* This is a bit overhead to use atomics in such a simple function called from many threads,
+   * but this allows to save quite measurable amount of memory. */
+  const int edge_index = atomic_fetch_and_add_z(&reshape_smooth_context->geometry.num_edges, 1);
+  BLI_assert(edge_index < reshape_smooth_context->geometry.max_edges);
+
+  Edge *edge = &reshape_smooth_context->geometry.edges[edge_index];
+  edge->v1 = subdiv_v1;
+  edge->v2 = subdiv_v2;
+  edge->sharpness = BKE_subdiv_edge_crease_to_sharpness_char(crease);
+}
+
 static void foreach_edge(const struct SubdivForeachContext *foreach_context,
                          void *UNUSED(tls),
                          const int coarse_edge_index,
@@ -682,8 +712,15 @@ static void foreach_edge(const struct SubdivForeachContext *foreach_context,
   MultiresReshapeSmoothContext *reshape_smooth_context = foreach_context->user_data;
   const MultiresReshapeContext *reshape_context = reshape_smooth_context->reshape_context;
 
-  /* Ignore all inner face edges as they have sharpness of zero. */
-  if (coarse_edge_index == ORIGINDEX_NONE) {
+  if (reshape_smooth_context->smoothing_type == MULTIRES_SUBDIVIDE_LINEAR) {
+    store_edge(reshape_smooth_context, subdiv_v1, subdiv_v2, (char)255);
+    return;
+  }
+
+  /* Ignore all inner face edges as they have sharpness of zero when using Catmull-Clark mode. In
+   * simple mode, all edges have maximum sharpness, so they can't be skipped. */
+  if (coarse_edge_index == ORIGINDEX_NONE &&
+      reshape_smooth_context->smoothing_type != MULTIRES_SUBDIVIDE_SIMPLE) {
     return;
   }
   /* Ignore all loose edges as well, as they are not communicated to the OpenSubdiv. */
@@ -697,16 +734,7 @@ static void foreach_edge(const struct SubdivForeachContext *foreach_context,
   if (crease == 0) {
     return;
   }
-
-  /* This is a bit overhead to use atomics in such a simple function called from many threads,
-   * but this allows to save quite measurable amount of memory. */
-  const int edge_index = atomic_fetch_and_add_z(&reshape_smooth_context->geometry.num_edges, 1);
-  BLI_assert(edge_index < reshape_smooth_context->geometry.max_edges);
-
-  Edge *edge = &reshape_smooth_context->geometry.edges[edge_index];
-  edge->v1 = subdiv_v1;
-  edge->v2 = subdiv_v2;
-  edge->sharpness = BKE_subdiv_edge_crease_to_sharpness_char(crease);
+  store_edge(reshape_smooth_context, subdiv_v1, subdiv_v2, crease);
 }
 
 static void geometry_init_loose_information(MultiresReshapeSmoothContext *reshape_smooth_context)
@@ -1212,7 +1240,12 @@ void multires_reshape_smooth_object_grids_with_details(
   }
 
   MultiresReshapeSmoothContext reshape_smooth_context;
-  context_init(&reshape_smooth_context, reshape_context);
+  if (reshape_context->mmd->simple) {
+    context_init(&reshape_smooth_context, reshape_context, MULTIRES_SUBDIVIDE_SIMPLE);
+  }
+  else {
+    context_init(&reshape_smooth_context, reshape_context, MULTIRES_SUBDIVIDE_CATMULL_CLARK);
+  }
 
   geometry_create(&reshape_smooth_context);
 
@@ -1228,7 +1261,8 @@ void multires_reshape_smooth_object_grids_with_details(
   context_free(&reshape_smooth_context);
 }
 
-void multires_reshape_smooth_object_grids(const MultiresReshapeContext *reshape_context)
+void multires_reshape_smooth_object_grids(const MultiresReshapeContext *reshape_context,
+                                          const eMultiresSubdivideModeType mode)
 {
   const int level_difference = (reshape_context->top.level - reshape_context->reshape.level);
   if (level_difference == 0) {
@@ -1237,7 +1271,7 @@ void multires_reshape_smooth_object_grids(const MultiresReshapeContext *reshape_
   }
 
   MultiresReshapeSmoothContext reshape_smooth_context;
-  context_init(&reshape_smooth_context, reshape_context);
+  context_init(&reshape_smooth_context, reshape_context, mode);
 
   geometry_create(&reshape_smooth_context);
 

source/blender/blenkernel/intern/multires_reshape_subdivide.c

@@ -0,0 +1,106 @@
+/*
+ * 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 "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 "BKE_subsurf.h"
+#include "BLI_math_vector.h"
+
+#include "DEG_depsgraph_query.h"
+
+#include "multires_reshape.h"
+
+void multires_subdivide_create_object_space_linear_grids(Mesh *mesh)
+{
+  MDisps *mdisps = CustomData_get_layer(&mesh->ldata, CD_MDISPS);
+  const int totpoly = mesh->totpoly;
+  for (int p = 0; p < totpoly; p++) {
+    MPoly *poly = &mesh->mpoly[p];
+    float poly_center[3];
+    BKE_mesh_calc_poly_center(poly, &mesh->mloop[poly->loopstart], mesh->mvert, poly_center);
+    for (int l = 0; l < poly->totloop; l++) {
+      const int loop_index = poly->loopstart + l;
+
+      float(*disps)[3] = mdisps[loop_index].disps;
+      mdisps[loop_index].totdisp = 4;
+      mdisps[loop_index].level = 1;
+
+      int prev_loop_index = l - 1 >= 0 ? loop_index - 1 : loop_index + poly->totloop - 1;
+      int next_loop_index = l + 1 < poly->totloop ? loop_index + 1 : poly->loopstart;
+
+      MLoop *loop = &mesh->mloop[loop_index];
+      MLoop *loop_next = &mesh->mloop[next_loop_index];
+      MLoop *loop_prev = &mesh->mloop[prev_loop_index];
+
+      copy_v3_v3(disps[0], poly_center);
+      mid_v3_v3v3(disps[1], mesh->mvert[loop->v].co, mesh->mvert[loop_next->v].co);
+      mid_v3_v3v3(disps[2], mesh->mvert[loop->v].co, mesh->mvert[loop_prev->v].co);
+      copy_v3_v3(disps[3], mesh->mvert[loop->v].co);
+    }
+  }
+}
+
+void multires_subdivide_create_tangent_displacement_linear_grids(Object *object,
+                                                                 MultiresModifierData *mmd)
+{
+  Mesh *coarse_mesh = object->data;
+  multires_force_sculpt_rebuild(object);
+
+  MultiresReshapeContext reshape_context;
+
+  const int new_top_level = mmd->totlvl + 1;
+
+  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 (new_top_level == 1) {
+    /* No MDISPS. Create new grids for level 1 using the edges mid point and poly centers. */
+    multires_reshape_ensure_grids(coarse_mesh, 1);
+    multires_subdivide_create_object_space_linear_grids(coarse_mesh);
+  }
+
+  /* Convert the new grids to tangent displacement. */
+  multires_set_tot_level(object, mmd, new_top_level);
+
+  if (!multires_reshape_context_create_from_subdivide(
+          &reshape_context, object, mmd, new_top_level)) {
+    return;
+  }
+
+  multires_reshape_object_grids_to_tangent_displacement(&reshape_context);
+  multires_reshape_context_free(&reshape_context);
+}

source/blender/editors/object/object_modifier.c

@@ -1433,6 +1433,25 @@ void OBJECT_OT_multires_higher_levels_delete(wmOperatorType *ot)
 /** \name Multires Subdivide Operator
  * \{ */
 
+static EnumPropertyItem prop_multires_subdivide_mode_type[] = {
+    {MULTIRES_SUBDIVIDE_CATMULL_CLARK,
+     "CATMULL_CLARK",
+     0,
+     "Catmull-Clark",
+     "Create a new level using Catmull-Clark subdivisions"},
+    {MULTIRES_SUBDIVIDE_SIMPLE,
+     "SIMPLE",
+     0,
+     "Simple",
+     "Create a new level using simple subdivisions"},
+    {MULTIRES_SUBDIVIDE_LINEAR,
+     "LINEAR",
+     0,
+     "Linear",
+     "Create a new level using linear interpolation of the sculpted displacement"},
+    {0, NULL, 0, NULL, NULL},
+};
+
 static int multires_subdivide_exec(bContext *C, wmOperator *op)
 {
   Object *object = ED_object_active_context(C);
@@ -1443,7 +1462,9 @@ static int multires_subdivide_exec(bContext *C, wmOperator *op)
     return OPERATOR_CANCELLED;
   }
 
-  multiresModifier_subdivide(object, mmd);
+  const eMultiresSubdivideModeType subdivide_mode = (eMultiresSubdivideModeType)(
+      RNA_enum_get(op->ptr, "mode"));
+  multiresModifier_subdivide(object, mmd, subdivide_mode);
 
   ED_object_iter_other(
       CTX_data_main(C), object, true, ED_object_multires_update_totlevels_cb, &mmd->totlvl);
@@ -1482,6 +1503,12 @@ void OBJECT_OT_multires_subdivide(wmOperatorType *ot)
   /* flags */
   ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO | OPTYPE_INTERNAL;
   edit_modifier_properties(ot);
+  RNA_def_enum(ot->srna,
+               "mode",
+               prop_multires_subdivide_mode_type,
+               MULTIRES_SUBDIVIDE_CATMULL_CLARK,
+               "Subdivision Mode",
+               "How the mesh is going to be subdivided to create a new level");
 }
 
 /** \} */