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, 29 insertions, 2 deletions

diff --git a/source/blender/editors/transform/transform_ops.c b/source/blender/editors/transform/transform_ops.c
index 5ed340abf97..80feb934f1a 100644
--- a/source/blender/editors/transform/transform_ops.c
+++ b/source/blender/editors/transform/transform_ops.c
@@ -78,6 +78,7 @@ static const char OP_BONE_SIZE[] = "TRANSFORM_OT_bbone_resize";
 static const char OP_EDGE_SLIDE[] = "TRANSFORM_OT_edge_slide";
 static const char OP_VERT_SLIDE[] = "TRANSFORM_OT_vert_slide";
 static const char OP_EDGE_CREASE[] = "TRANSFORM_OT_edge_crease";
+static const char OP_VERT_CREASE[] = "TRANSFORM_OT_vert_crease";
 static const char OP_EDGE_BWEIGHT[] = "TRANSFORM_OT_edge_bevelweight";
 static const char OP_SEQ_SLIDE[] = "TRANSFORM_OT_seq_slide";
 static const char OP_NORMAL_ROTATION[] = "TRANSFORM_OT_rotate_normal";
@@ -98,6 +99,7 @@ static void TRANSFORM_OT_bbone_resize(struct wmOperatorType *ot);
 static void TRANSFORM_OT_edge_slide(struct wmOperatorType *ot);
 static void TRANSFORM_OT_vert_slide(struct wmOperatorType *ot);
 static void TRANSFORM_OT_edge_crease(struct wmOperatorType *ot);
+static void TRANSFORM_OT_vert_crease(struct wmOperatorType *ot);
 static void TRANSFORM_OT_edge_bevelweight(struct wmOperatorType *ot);
 static void TRANSFORM_OT_seq_slide(struct wmOperatorType *ot);
 static void TRANSFORM_OT_rotate_normal(struct wmOperatorType *ot);
@@ -118,7 +120,8 @@ static TransformModeItem transform_modes[] = {
     {OP_BONE_SIZE, TFM_BONESIZE, TRANSFORM_OT_bbone_resize},
     {OP_EDGE_SLIDE, TFM_EDGE_SLIDE, TRANSFORM_OT_edge_slide},
     {OP_VERT_SLIDE, TFM_VERT_SLIDE, TRANSFORM_OT_vert_slide},
-    {OP_EDGE_CREASE, TFM_CREASE, TRANSFORM_OT_edge_crease},
+    {OP_EDGE_CREASE, TFM_EDGE_CREASE, TRANSFORM_OT_edge_crease},
+    {OP_VERT_CREASE, TFM_VERT_CREASE, TRANSFORM_OT_vert_crease},
     {OP_EDGE_BWEIGHT, TFM_BWEIGHT, TRANSFORM_OT_edge_bevelweight},
     {OP_SEQ_SLIDE, TFM_SEQ_SLIDE, TRANSFORM_OT_seq_slide},
     {OP_NORMAL_ROTATION, TFM_NORMAL_ROTATION, TRANSFORM_OT_rotate_normal},
@@ -139,7 +142,8 @@ const EnumPropertyItem rna_enum_transform_mode_types[] = {
     {TFM_TILT, "TILT", 0, "Tilt", ""},
     {TFM_TRACKBALL, "TRACKBALL", 0, "Trackball", ""},
     {TFM_PUSHPULL, "PUSHPULL", 0, "Push/Pull", ""},
-    {TFM_CREASE, "CREASE", 0, "Crease", ""},
+    {TFM_EDGE_CREASE, "CREASE", 0, "Crease", ""},
+    {TFM_VERT_CREASE, "VERTEX_CREASE", 0, "Vertex Crease", ""},
     {TFM_MIRROR, "MIRROR", 0, "Mirror", ""},
     {TFM_BONESIZE, "BONE_SIZE", 0, "Bone Size", ""},
     {TFM_BONE_ENVELOPE, "BONE_ENVELOPE", 0, "Bone Envelope", ""},
@@ -1196,6 +1200,29 @@ static void TRANSFORM_OT_edge_crease(struct wmOperatorType *ot)
   Transform_Properties(ot, P_SNAP);
 }
 
+static void TRANSFORM_OT_vert_crease(struct wmOperatorType *ot)
+{
+  /* identifiers */
+  ot->name = "Vertex Crease";
+  ot->description = "Change the crease of vertices";
+  ot->idname = OP_VERT_CREASE;
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO | OPTYPE_BLOCKING;
+
+  /* api callbacks */
+  ot->invoke = transform_invoke;
+  ot->exec = transform_exec;
+  ot->modal = transform_modal;
+  ot->cancel = transform_cancel;
+  ot->poll = ED_operator_editmesh;
+  ot->poll_property = transform_poll_property;
+
+  RNA_def_float_factor(ot->srna, "value", 0, -1.0f, 1.0f, "Factor", "", -1.0f, 1.0f);
+
+  WM_operatortype_props_advanced_begin(ot);
+
+  Transform_Properties(ot, P_SNAP);
+}
+
 static void TRANSFORM_OT_edge_bevelweight(struct wmOperatorType *ot)
 {
   /* identifiers */