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, 53 insertions, 13 deletions

diff --git a/source/blender/editors/space_view3d/view3d_buttons.c b/source/blender/editors/space_view3d/view3d_buttons.c
index 5451aa5a2e0..243d4033cbc 100644
--- a/source/blender/editors/space_view3d/view3d_buttons.c
+++ b/source/blender/editors/space_view3d/view3d_buttons.c
@@ -87,7 +87,7 @@ typedef struct {
 } TransformMedian_Generic;
 
 typedef struct {
-  float location[3], bv_weight, be_weight, skin[2], crease;
+  float location[3], bv_weight, v_crease, be_weight, skin[2], e_crease;
 } TransformMedian_Mesh;
 
 typedef struct {
@@ -319,6 +319,7 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
     BMIter iter;
 
     const int cd_vert_bweight_offset = CustomData_get_offset(&bm->vdata, CD_BWEIGHT);
+    const int cd_vert_crease_offset = CustomData_get_offset(&bm->vdata, CD_CREASE);
     const int cd_vert_skin_offset = CustomData_get_offset(&bm->vdata, CD_MVERT_SKIN);
     const int cd_edge_bweight_offset = CustomData_get_offset(&bm->edata, CD_BWEIGHT);
     const int cd_edge_crease_offset = CustomData_get_offset(&bm->edata, CD_CREASE);
@@ -335,6 +336,10 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
             median->bv_weight += BM_ELEM_CD_GET_FLOAT(eve, cd_vert_bweight_offset);
           }
 
+          if (cd_vert_crease_offset != -1) {
+            median->v_crease += BM_ELEM_CD_GET_FLOAT(eve, cd_vert_crease_offset);
+          }
+
           if (has_skinradius) {
             MVertSkin *vs = BM_ELEM_CD_GET_VOID_P(eve, cd_vert_skin_offset);
             add_v2_v2(median->skin, vs->radius); /* Third val not used currently. */
@@ -352,7 +357,7 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
             }
 
             if (cd_edge_crease_offset != -1) {
-              median->crease += BM_ELEM_CD_GET_FLOAT(eed, cd_edge_crease_offset);
+              median->e_crease += BM_ELEM_CD_GET_FLOAT(eed, cd_edge_crease_offset);
             }
 
             totedgedata++;
@@ -489,11 +494,12 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
   if (has_meshdata) {
     TransformMedian_Mesh *median = &median_basis.mesh;
     if (totedgedata) {
-      median->crease /= (float)totedgedata;
+      median->e_crease /= (float)totedgedata;
       median->be_weight /= (float)totedgedata;
     }
     if (tot) {
       median->bv_weight /= (float)tot;
+      median->v_crease /= (float)tot;
       if (has_skinradius) {
         median->skin[0] /= (float)tot;
         median->skin[1] /= (float)tot;
@@ -683,6 +689,23 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
                         TIP_("Vertex weight used by Bevel modifier"));
         UI_but_number_step_size_set(but, 1);
         UI_but_number_precision_set(but, 2);
+        /* customdata layer added on demand */
+        but = uiDefButF(block,
+                        UI_BTYPE_NUM,
+                        B_TRANSFORM_PANEL_MEDIAN,
+                        tot == 1 ? IFACE_("Vertex Crease:") : IFACE_("Mean Vertex Crease:"),
+                        0,
+                        yi -= buth + but_margin,
+                        butw,
+                        buth,
+                        &ve_median->v_crease,
+                        0.0,
+                        1.0,
+                        0,
+                        0,
+                        TIP_("Weight used by the Subdivision Surface modifier"));
+        UI_but_number_step_size_set(but, 1);
+        UI_but_number_precision_set(but, 2);
       }
       if (has_skinradius) {
         UI_block_align_begin(block);
@@ -761,7 +784,7 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
                         yi -= buth + but_margin,
                         butw,
                         buth,
-                        &ve_median->crease,
+                        &ve_median->e_crease,
                         0.0,
                         1.0,
                         0,
@@ -958,8 +981,9 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
     const bool apply_vcos = (tot == 1) || (len_squared_v3(median_basis.generic.location) != 0.0f);
 
     if ((ob->type == OB_MESH) &&
-        (apply_vcos || median_basis.mesh.bv_weight || median_basis.mesh.skin[0] ||
-         median_basis.mesh.skin[1] || median_basis.mesh.be_weight || median_basis.mesh.crease)) {
+        (apply_vcos || median_basis.mesh.bv_weight || median_basis.mesh.v_crease ||
+         median_basis.mesh.skin[0] || median_basis.mesh.skin[1] || median_basis.mesh.be_weight ||
+         median_basis.mesh.e_crease)) {
       const TransformMedian_Mesh *median = &median_basis.mesh, *ve_median = &ve_median_basis.mesh;
       Mesh *me = ob->data;
       BMEditMesh *em = me->edit_mesh;
@@ -969,18 +993,21 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
       BMEdge *eed;
 
       int cd_vert_bweight_offset = -1;
+      int cd_vert_crease_offset = -1;
       int cd_vert_skin_offset = -1;
       int cd_edge_bweight_offset = -1;
       int cd_edge_crease_offset = -1;
 
       float scale_bv_weight = 1.0f;
+      float scale_v_crease = 1.0f;
       float scale_skin[2] = {1.0f, 1.0f};
       float scale_be_weight = 1.0f;
-      float scale_crease = 1.0f;
+      float scale_e_crease = 1.0f;
 
       /* Vertices */
 
-      if (apply_vcos || median->bv_weight || median->skin[0] || median->skin[1]) {
+      if (apply_vcos || median->bv_weight || median->v_crease || median->skin[0] ||
+          median->skin[1]) {
         if (median->bv_weight) {
           BM_mesh_cd_flag_ensure(bm, me, ME_CDFLAG_VERT_BWEIGHT);
           cd_vert_bweight_offset = CustomData_get_offset(&bm->vdata, CD_BWEIGHT);
@@ -989,6 +1016,14 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
           scale_bv_weight = compute_scale_factor(ve_median->bv_weight, median->bv_weight);
         }
 
+        if (median->v_crease) {
+          BM_mesh_cd_flag_ensure(bm, me, ME_CDFLAG_VERT_CREASE);
+          cd_vert_crease_offset = CustomData_get_offset(&bm->vdata, CD_CREASE);
+          BLI_assert(cd_vert_crease_offset != -1);
+
+          scale_v_crease = compute_scale_factor(ve_median->v_crease, median->v_crease);
+        }
+
         for (int i = 0; i < 2; i++) {
           if (median->skin[i]) {
             cd_vert_skin_offset = CustomData_get_offset(&bm->vdata, CD_MVERT_SKIN);
@@ -1011,6 +1046,11 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
               apply_scale_factor_clamp(b_weight, tot, ve_median->bv_weight, scale_bv_weight);
             }
 
+            if (cd_vert_crease_offset != -1) {
+              float *crease = BM_ELEM_CD_GET_VOID_P(eve, cd_vert_crease_offset);
+              apply_scale_factor_clamp(crease, tot, ve_median->v_crease, scale_v_crease);
+            }
+
             if (cd_vert_skin_offset != -1) {
               MVertSkin *vs = BM_ELEM_CD_GET_VOID_P(eve, cd_vert_skin_offset);
 
@@ -1033,7 +1073,7 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
 
       /* Edges */
 
-      if (median->be_weight || median->crease) {
+      if (median->be_weight || median->e_crease) {
         if (median->be_weight) {
           BM_mesh_cd_flag_ensure(bm, me, ME_CDFLAG_EDGE_BWEIGHT);
           cd_edge_bweight_offset = CustomData_get_offset(&bm->edata, CD_BWEIGHT);
@@ -1042,12 +1082,12 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
           scale_be_weight = compute_scale_factor(ve_median->be_weight, median->be_weight);
         }
 
-        if (median->crease) {
+        if (median->e_crease) {
           BM_mesh_cd_flag_ensure(bm, me, ME_CDFLAG_EDGE_CREASE);
           cd_edge_crease_offset = CustomData_get_offset(&bm->edata, CD_CREASE);
           BLI_assert(cd_edge_crease_offset != -1);
 
-          scale_crease = compute_scale_factor(ve_median->crease, median->crease);
+          scale_e_crease = compute_scale_factor(ve_median->e_crease, median->e_crease);
         }
 
         BM_ITER_MESH (eed, &iter, bm, BM_EDGES_OF_MESH) {
@@ -1057,9 +1097,9 @@ static void v3d_editvertex_buts(uiLayout *layout, View3D *v3d, Object *ob, float
               apply_scale_factor_clamp(b_weight, tot, ve_median->be_weight, scale_be_weight);
             }
 
-            if (median->crease != 0.0f) {
+            if (median->e_crease != 0.0f) {
               float *crease = BM_ELEM_CD_GET_VOID_P(eed, cd_edge_crease_offset);
-              apply_scale_factor_clamp(crease, tot, ve_median->crease, scale_crease);
+              apply_scale_factor_clamp(crease, tot, ve_median->e_crease, scale_e_crease);
             }
           }
         }