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

1 files changed, 10 insertions, 5 deletions

diff --git a/source/blender/blenkernel/intern/subdiv_converter_mesh.c b/source/blender/blenkernel/intern/subdiv_converter_mesh.c
index 41fc28c5d52..fc7ef887879 100644
--- a/source/blender/blenkernel/intern/subdiv_converter_mesh.c
+++ b/source/blender/blenkernel/intern/subdiv_converter_mesh.c
@@ -40,6 +40,8 @@
 #include "opensubdiv_capi.h"
 #include "opensubdiv_converter_capi.h"
 
+#include "bmesh_class.h"
+
 /* Enable work-around for non-working CPU evaluator when using bilinear scheme.
  * This forces Catmark scheme with all edges marked as infinitely sharp. */
 #define BUGGY_SIMPLE_SCHEME_WORKAROUND 1
@@ -47,6 +49,8 @@
 typedef struct ConverterStorage {
   SubdivSettings settings;
   const Mesh *mesh;
+  /* CustomData layer for vertex sharpnesses. */
+  const float *cd_vertex_crease;
   /* Indexed by loop index, value denotes index of face-varying vertex
    * which corresponds to the UV coordinate.
    */
@@ -168,7 +172,7 @@ static float get_edge_sharpness(const OpenSubdiv_Converter *converter, int manif
   }
   const int edge_index = storage->manifold_edge_index_reverse[manifold_edge_index];
   const MEdge *medge = storage->mesh->medge;
-  return BKE_subdiv_edge_crease_to_sharpness_char(medge[edge_index].crease);
+  return BKE_subdiv_crease_to_sharpness_char(medge[edge_index].crease);
 }
 
 static bool is_infinite_sharp_vertex(const OpenSubdiv_Converter *converter,
@@ -184,14 +188,14 @@ static bool is_infinite_sharp_vertex(const OpenSubdiv_Converter *converter,
   return BLI_BITMAP_TEST_BOOL(storage->infinite_sharp_vertices_map, vertex_index);
 }
 
-static float get_vertex_sharpness(const OpenSubdiv_Converter *converter,
-                                  int UNUSED(manifold_vertex_index))
+static float get_vertex_sharpness(const OpenSubdiv_Converter *converter, int manifold_vertex_index)
 {
   ConverterStorage *storage = converter->user_data;
-  if (!storage->settings.use_creases) {
+  if (!storage->settings.use_creases || storage->cd_vertex_crease == NULL) {
     return 0.0f;
   }
-  return 0.0f;
+  const int vertex_index = storage->manifold_vertex_index_reverse[manifold_vertex_index];
+  return BKE_subdiv_crease_to_sharpness_f(storage->cd_vertex_crease[vertex_index]);
 }
 
 static int get_num_uv_layers(const OpenSubdiv_Converter *converter)
@@ -393,6 +397,7 @@ static void init_user_data(OpenSubdiv_Converter *converter,
   ConverterStorage *user_data = MEM_mallocN(sizeof(ConverterStorage), __func__);
   user_data->settings = *settings;
   user_data->mesh = mesh;
+  user_data->cd_vertex_crease = CustomData_get_layer(&mesh->vdata, CD_CREASE);
   user_data->loop_uv_indices = NULL;
   initialize_manifold_indices(user_data);
   converter->user_data = user_data;