Subdivision: add support for vertex creasing

This adds vertex creasing support for OpenSubDiv for modeling, rendering,
Alembic and USD I/O.

For modeling, vertex creasing follows the edge creasing implementation with an
operator accessible through the Vertex menu in Edit Mode, and some parameter in
the properties panel. The option in the Subsurf and Multires to use edge
creasing also affects vertex creasing.

The vertex crease data is stored as a CustomData layer, unlike edge creases
which for now are stored in `MEdge`, but will in the future also be moved to
a `CustomData` layer. See comments for details on the difference in behavior
for the `CD_CREASE` layer between egdes and vertices.

For Cycles this adds sockets on the Mesh node to hold data about which vertices
are creased (one socket for the indices, one for the weigths).

Viewport rendering of vertex creasing reuses the same color scheme as for edges
and creased vertices are drawn bigger than uncreased vertices.

For Alembic and USD, vertex crease support follows the edge crease
implementation, they are always read, but only exported if a `Subsurf` modifier
is present on the Mesh.

Reviewed By: brecht, fclem, sergey, sybren, campbellbarton

Differential Revision: https://developer.blender.org/D10145

2 files changed, 77 insertions, 15 deletions

diff --git a/source/blender/io/alembic/exporter/abc_writer_mesh.cc b/source/blender/io/alembic/exporter/abc_writer_mesh.cc
index 7275d0addf0..6ab4b06fba6 100644
--- a/source/blender/io/alembic/exporter/abc_writer_mesh.cc
+++ b/source/blender/io/alembic/exporter/abc_writer_mesh.cc
@@ -76,10 +76,13 @@ static void get_topology(struct Mesh *mesh,
                          std::vector<int32_t> &poly_verts,
                          std::vector<int32_t> &loop_counts,
                          bool &r_has_flat_shaded_poly);
-static void get_creases(struct Mesh *mesh,
-                        std::vector<int32_t> &indices,
-                        std::vector<int32_t> &lengths,
-                        std::vector<float> &sharpnesses);
+static void get_edge_creases(struct Mesh *mesh,
+                             std::vector<int32_t> &indices,
+                             std::vector<int32_t> &lengths,
+                             std::vector<float> &sharpnesses);
+static void get_vert_creases(struct Mesh *mesh,
+                             std::vector<int32_t> &indices,
+                             std::vector<float> &sharpnesses);
 static void get_loop_normals(struct Mesh *mesh,
                              std::vector<Imath::V3f> &normals,
                              bool has_flat_shaded_poly);
@@ -283,15 +286,16 @@ void ABCGenericMeshWriter::write_mesh(HierarchyContext &context, Mesh *mesh)
 
 void ABCGenericMeshWriter::write_subd(HierarchyContext &context, struct Mesh *mesh)
 {
-  std::vector<float> crease_sharpness;
+  std::vector<float> edge_crease_sharpness, vert_crease_sharpness;
   std::vector<Imath::V3f> points;
   std::vector<int32_t> poly_verts, loop_counts;
-  std::vector<int32_t> crease_indices, crease_lengths;
+  std::vector<int32_t> edge_crease_indices, edge_crease_lengths, vert_crease_indices;
   bool has_flat_poly = false;
 
   get_vertices(mesh, points);
   get_topology(mesh, poly_verts, loop_counts, has_flat_poly);
-  get_creases(mesh, crease_indices, crease_lengths, crease_sharpness);
+  get_edge_creases(mesh, edge_crease_indices, edge_crease_lengths, edge_crease_sharpness);
+  get_vert_creases(mesh, vert_crease_indices, vert_crease_sharpness);
 
   if (!frame_has_been_written_ && args_.export_params->face_sets) {
     write_face_sets(context.object, mesh, abc_subdiv_schema_);
@@ -322,10 +326,15 @@ void ABCGenericMeshWriter::write_subd(HierarchyContext &context, struct Mesh *me
     write_generated_coordinates(abc_poly_mesh_schema_.getArbGeomParams(), m_custom_data_config);
   }
 
-  if (!crease_indices.empty()) {
-    subdiv_sample.setCreaseIndices(Int32ArraySample(crease_indices));
-    subdiv_sample.setCreaseLengths(Int32ArraySample(crease_lengths));
-    subdiv_sample.setCreaseSharpnesses(FloatArraySample(crease_sharpness));
+  if (!edge_crease_indices.empty()) {
+    subdiv_sample.setCreaseIndices(Int32ArraySample(edge_crease_indices));
+    subdiv_sample.setCreaseLengths(Int32ArraySample(edge_crease_lengths));
+    subdiv_sample.setCreaseSharpnesses(FloatArraySample(edge_crease_sharpness));
+  }
+
+  if (!vert_crease_indices.empty()) {
+    subdiv_sample.setCornerIndices(Int32ArraySample(vert_crease_indices));
+    subdiv_sample.setCornerSharpnesses(FloatArraySample(vert_crease_sharpness));
   }
 
   update_bounding_box(context.object);
@@ -477,10 +486,10 @@ static void get_topology(struct Mesh *mesh,
   }
 }
 
-static void get_creases(struct Mesh *mesh,
-                        std::vector<int32_t> &indices,
-                        std::vector<int32_t> &lengths,
-                        std::vector<float> &sharpnesses)
+static void get_edge_creases(struct Mesh *mesh,
+                             std::vector<int32_t> &indices,
+                             std::vector<int32_t> &lengths,
+                             std::vector<float> &sharpnesses)
 {
   const float factor = 1.0f / 255.0f;
 
@@ -503,6 +512,29 @@ static void get_creases(struct Mesh *mesh,
   lengths.resize(sharpnesses.size(), 2);
 }
 
+static void get_vert_creases(struct Mesh *mesh,
+                             std::vector<int32_t> &indices,
+                             std::vector<float> &sharpnesses)
+{
+  indices.clear();
+  sharpnesses.clear();
+
+  const float *creases = static_cast<const float *>(CustomData_get_layer(&mesh->vdata, CD_CREASE));
+
+  if (!creases) {
+    return;
+  }
+
+  for (int i = 0, v = mesh->totvert; i < v; i++) {
+    const float sharpness = creases[i];
+
+    if (sharpness != 0.0f) {
+      indices.push_back(i);
+      sharpnesses.push_back(sharpness);
+    }
+  }
+}
+
 static void get_loop_normals(struct Mesh *mesh,
                              std::vector<Imath::V3f> &normals,
                              bool has_flat_shaded_poly)
diff --git a/source/blender/io/alembic/intern/abc_reader_mesh.cc b/source/blender/io/alembic/intern/abc_reader_mesh.cc
index 3c1ac8ceeaf..bd40eb35123 100644
--- a/source/blender/io/alembic/intern/abc_reader_mesh.cc
+++ b/source/blender/io/alembic/intern/abc_reader_mesh.cc
@@ -45,6 +45,7 @@
 #include "BKE_modifier.h"
 #include "BKE_object.h"
 
+using Alembic::Abc::FloatArraySamplePtr;
 using Alembic::Abc::Int32ArraySamplePtr;
 using Alembic::Abc::IV3fArrayProperty;
 using Alembic::Abc::P3fArraySamplePtr;
@@ -910,6 +911,32 @@ static void read_subd_sample(const std::string &iobject_full_name,
   }
 }
 
+static void read_vertex_creases(Mesh *mesh,
+                                const Int32ArraySamplePtr &indices,
+                                const FloatArraySamplePtr &sharpnesses)
+{
+  if (!(indices && sharpnesses && indices->size() == sharpnesses->size() &&
+        indices->size() != 0)) {
+    return;
+  }
+
+  float *vertex_crease_data = (float *)CustomData_add_layer(
+      &mesh->vdata, CD_CREASE, CD_DEFAULT, nullptr, mesh->totvert);
+  const int totvert = mesh->totvert;
+
+  for (int i = 0, v = indices->size(); i < v; ++i) {
+    const int idx = (*indices)[i];
+
+    if (idx >= totvert) {
+      continue;
+    }
+
+    vertex_crease_data[idx] = (*sharpnesses)[i];
+  }
+
+  mesh->cd_flag |= ME_CDFLAG_VERT_CREASE;
+}
+
 /* ************************************************************************** */
 
 AbcSubDReader::AbcSubDReader(const IObject &object, ImportSettings &settings)
@@ -973,6 +1000,7 @@ void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
     return;
   }
 
+  /* Read egde creases. */
   Int32ArraySamplePtr indices = sample.getCreaseIndices();
   Alembic::Abc::FloatArraySamplePtr sharpnesses = sample.getCreaseSharpnesses();
 
@@ -1003,6 +1031,8 @@ void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
     mesh->cd_flag |= ME_CDFLAG_EDGE_CREASE;
   }
 
+  read_vertex_creases(mesh, sample.getCornerIndices(), sample.getCornerSharpnesses());
+
   if (m_settings->validate_meshes) {
     BKE_mesh_validate(mesh, false, false);
   }