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, 18 insertions, 7 deletions

diff --git a/source/blender/blenkernel/intern/customdata.cc b/source/blender/blenkernel/intern/customdata.cc
index feb5ecb8f04..e1bc025efd2 100644
--- a/source/blender/blenkernel/intern/customdata.cc
+++ b/source/blender/blenkernel/intern/customdata.cc
@@ -1692,7 +1692,9 @@ static const LayerTypeInfo LAYERTYPEINFO[CD_NUMTYPES] = {
     /* 29: CD_BWEIGHT */
     {sizeof(float), "", 0, N_("BevelWeight"), nullptr, nullptr, layerInterp_bweight},
     /* 30: CD_CREASE */
-    {sizeof(float), "", 0, N_("SubSurfCrease"), nullptr, nullptr, layerInterp_bweight},
+    /* NOTE: we do not interpolate crease data as it should be either inherited for subdivided
+     * edges, or for vertex creases, only present on the original vertex. */
+    {sizeof(float), "", 0, N_("SubSurfCrease"), nullptr, nullptr, nullptr},
     /* 31: CD_ORIGSPACE_MLOOP */
     {sizeof(OrigSpaceLoop),
      "OrigSpaceLoop",
@@ -1938,7 +1940,7 @@ const CustomData_MeshMasks CD_MASK_BAREMESH_ORIGINDEX = {
 };
 const CustomData_MeshMasks CD_MASK_MESH = {
     /* vmask */ (CD_MASK_MVERT | CD_MASK_MDEFORMVERT | CD_MASK_MVERT_SKIN | CD_MASK_PAINT_MASK |
-                 CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR),
+                 CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR | CD_MASK_CREASE),
     /* emask */ (CD_MASK_MEDGE | CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
     /* fmask */ 0,
     /* pmask */
@@ -1950,7 +1952,7 @@ const CustomData_MeshMasks CD_MASK_MESH = {
 };
 const CustomData_MeshMasks CD_MASK_EDITMESH = {
     /* vmask */ (CD_MASK_MDEFORMVERT | CD_MASK_PAINT_MASK | CD_MASK_MVERT_SKIN | CD_MASK_SHAPEKEY |
-                 CD_MASK_SHAPE_KEYINDEX | CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR),
+                 CD_MASK_SHAPE_KEYINDEX | CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR | CD_MASK_CREASE),
     /* emask */ (CD_MASK_PROP_ALL),
     /* fmask */ 0,
     /* pmask */ (CD_MASK_FACEMAP | CD_MASK_PROP_ALL | CD_MASK_SCULPT_FACE_SETS),
@@ -1961,7 +1963,7 @@ const CustomData_MeshMasks CD_MASK_EDITMESH = {
 const CustomData_MeshMasks CD_MASK_DERIVEDMESH = {
     /* vmask */ (CD_MASK_ORIGINDEX | CD_MASK_MDEFORMVERT | CD_MASK_SHAPEKEY | CD_MASK_MVERT_SKIN |
                  CD_MASK_PAINT_MASK | CD_MASK_ORCO | CD_MASK_CLOTH_ORCO | CD_MASK_PROP_ALL |
-                 CD_MASK_PROP_COLOR),
+                 CD_MASK_PROP_COLOR | CD_MASK_CREASE),
     /* emask */ (CD_MASK_ORIGINDEX | CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
     /* fmask */ (CD_MASK_ORIGINDEX | CD_MASK_ORIGSPACE | CD_MASK_PREVIEW_MCOL | CD_MASK_TANGENT),
     /* pmask */
@@ -1974,7 +1976,7 @@ const CustomData_MeshMasks CD_MASK_DERIVEDMESH = {
 const CustomData_MeshMasks CD_MASK_BMESH = {
     /* vmask */ (CD_MASK_MDEFORMVERT | CD_MASK_BWEIGHT | CD_MASK_MVERT_SKIN | CD_MASK_SHAPEKEY |
                  CD_MASK_SHAPE_KEYINDEX | CD_MASK_PAINT_MASK | CD_MASK_PROP_ALL |
-                 CD_MASK_PROP_COLOR),
+                 CD_MASK_PROP_COLOR | CD_MASK_CREASE),
     /* emask */ (CD_MASK_BWEIGHT | CD_MASK_CREASE | CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
     /* fmask */ 0,
     /* pmask */
@@ -2001,7 +2003,7 @@ const CustomData_MeshMasks CD_MASK_EVERYTHING = {
     /* vmask */ (CD_MASK_MVERT | CD_MASK_BM_ELEM_PYPTR | CD_MASK_ORIGINDEX | CD_MASK_NORMAL |
                  CD_MASK_MDEFORMVERT | CD_MASK_BWEIGHT | CD_MASK_MVERT_SKIN | CD_MASK_ORCO |
                  CD_MASK_CLOTH_ORCO | CD_MASK_SHAPEKEY | CD_MASK_SHAPE_KEYINDEX |
-                 CD_MASK_PAINT_MASK | CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR),
+                 CD_MASK_PAINT_MASK | CD_MASK_PROP_ALL | CD_MASK_PROP_COLOR | CD_MASK_CREASE),
     /* emask */
     (CD_MASK_MEDGE | CD_MASK_BM_ELEM_PYPTR | CD_MASK_ORIGINDEX | CD_MASK_BWEIGHT | CD_MASK_CREASE |
      CD_MASK_FREESTYLE_EDGE | CD_MASK_PROP_ALL),
@@ -4409,7 +4411,12 @@ bool CustomData_verify_versions(struct CustomData *data, int index)
     /* 0 structnum is used in writing code to tag layer types that should not be written. */
     else if (typeInfo->structnum == 0 &&
              /* XXX Not sure why those three are exception, maybe that should be fixed? */
-             !ELEM(layer->type, CD_PAINT_MASK, CD_FACEMAP, CD_MTEXPOLY, CD_SCULPT_FACE_SETS)) {
+             !ELEM(layer->type,
+                   CD_PAINT_MASK,
+                   CD_FACEMAP,
+                   CD_MTEXPOLY,
+                   CD_SCULPT_FACE_SETS,
+                   CD_CREASE)) {
       keeplayer = false;
       CLOG_WARN(&LOG, ".blend file read: removing a data layer that should not have been written");
     }
@@ -5080,6 +5087,10 @@ void CustomData_blend_write(BlendWriter *writer,
       const bool *layer_data = static_cast<const bool *>(layer->data);
       BLO_write_raw(writer, sizeof(*layer_data) * count, layer_data);
     }
+    else if (layer->type == CD_CREASE) {
+      const float *layer_data = static_cast<const float *>(layer->data);
+      BLO_write_raw(writer, sizeof(*layer_data) * count, layer_data);
+    }
     else {
       const char *structname;
       int structnum;