Sculpt: Upload white for color attributes in multires in sculpt

Even if multires in sculpt mode doesn't yet support color
attributes, we should at least upload white color to avoid
making everything black.

Also fixed a bug where multires PBVHs didn't have access to
their CustomData attribute layout, which PBVH draw needs.

4 files changed, 27 insertions, 3 deletions

diff --git a/source/blender/blenkernel/BKE_pbvh.h b/source/blender/blenkernel/BKE_pbvh.h
index 9e0884a8c76..467a7c7f306 100644
--- a/source/blender/blenkernel/BKE_pbvh.h
+++ b/source/blender/blenkernel/BKE_pbvh.h
@@ -265,7 +265,8 @@ void BKE_pbvh_build_grids(PBVH *pbvh,
                           struct CCGKey *key,
                           void **gridfaces,
                           struct DMFlagMat *flagmats,
-                          unsigned int **grid_hidden);
+                          unsigned int **grid_hidden,
+                          struct Mesh *me);
 /**
  * Build a PBVH from a BMesh.
  */
diff --git a/source/blender/blenkernel/intern/paint.cc b/source/blender/blenkernel/intern/paint.cc
index e0a27a3d03e..f7f5f7e411a 100644
--- a/source/blender/blenkernel/intern/paint.cc
+++ b/source/blender/blenkernel/intern/paint.cc
@@ -2240,7 +2240,8 @@ static PBVH *build_pbvh_from_ccg(Object *ob, SubdivCCG *subdiv_ccg, bool respect
                        &key,
                        (void **)subdiv_ccg->grid_faces,
                        subdiv_ccg->grid_flag_mats,
-                       subdiv_ccg->grid_hidden);
+                       subdiv_ccg->grid_hidden,
+                       base_mesh);
   pbvh_show_mask_set(pbvh, ob->sculpt->show_mask);
   pbvh_show_face_sets_set(pbvh, ob->sculpt->show_face_sets);
   return pbvh;
diff --git a/source/blender/blenkernel/intern/pbvh.c b/source/blender/blenkernel/intern/pbvh.c
index 5061fecbccb..a7595952cac 100644
--- a/source/blender/blenkernel/intern/pbvh.c
+++ b/source/blender/blenkernel/intern/pbvh.c
@@ -663,7 +663,8 @@ void BKE_pbvh_build_grids(PBVH *pbvh,
                           CCGKey *key,
                           void **gridfaces,
                           DMFlagMat *flagmats,
-                          BLI_bitmap **grid_hidden)
+                          BLI_bitmap **grid_hidden,
+                          Mesh *me)
 {
   const int gridsize = key->grid_size;
 
@@ -676,6 +677,14 @@ void BKE_pbvh_build_grids(PBVH *pbvh,
   pbvh->grid_hidden = grid_hidden;
   pbvh->leaf_limit = max_ii(LEAF_LIMIT / (gridsize * gridsize), 1);
 
+  /* We need the base mesh attribute layout for PBVH draw. */
+  pbvh->vdata = &me->vdata;
+  pbvh->ldata = &me->ldata;
+  pbvh->pdata = &me->pdata;
+
+  /* We also need the base mesh for PBVH draw. */
+  pbvh->mesh = me;
+
   BB cb;
   BB_reset(&cb);
 
diff --git a/source/blender/draw/intern/draw_pbvh.cc b/source/blender/draw/intern/draw_pbvh.cc
index fbee8313041..e0231e36e8e 100644
--- a/source/blender/draw/intern/draw_pbvh.cc
+++ b/source/blender/draw/intern/draw_pbvh.cc
@@ -345,6 +345,19 @@ struct PBVHBatches {
     GPU_vertbuf_attr_get_raw_data(vbo.vert_buf, 0, &access);
 
     switch (vbo.type) {
+      case CD_PROP_COLOR:
+      case CD_PROP_BYTE_COLOR: {
+        /* TODO: Implement color support for multires similar to the mesh cache
+         * extractor code. For now just upload white.
+         */
+        const ushort4 white(USHRT_MAX, USHRT_MAX, USHRT_MAX, USHRT_MAX);
+
+        foreach_grids(
+            [&](int /*x*/, int /*y*/, int /*grid_index*/, CCGElem * /*elems*/[4], int /*i*/) {
+              *static_cast<ushort4 *>(GPU_vertbuf_raw_step(&access)) = white;
+            });
+        break;
+      }
       case CD_PBVH_CO_TYPE:
         foreach_grids([&](int /*x*/, int /*y*/, int /*grid_index*/, CCGElem *elems[4], int i) {
           float *co = CCG_elem_co(&args->ccg_key, elems[i]);