Hidden PBVH nodes:

Set hidden when rebuilding the PBVH tree if all primitives are hidden.

source/blender/blenkernel/BKE_pbvh.h

@@ -128,6 +128,10 @@ void BKE_pbvh_bounding_box(const PBVH *bvh, float min[3], float max[3]);
 /* multires hidden data, only valid for type == PBVH_GRIDS */
 unsigned int **BKE_pbvh_grid_hidden(const PBVH *bvh);
 
+int BKE_pbvh_count_grid_quads(BLI_bitmap **grid_hidden,
+								int *grid_indices, int totgrid,
+								int gridsize);
+
 /* multires level, only valid for type == PBVH_GRIDS */
 void BKE_pbvh_get_grid_key(const PBVH *pbvh, struct CCGKey *key);
 

source/blender/blenkernel/intern/pbvh.c

@@ -275,6 +275,7 @@ static void build_mesh_leaf_node(PBVH *bvh, PBVHNode *node)
 	GHashIterator *iter;
 	GHash *map;
 	int i, j, totface;
+	bool has_visible = false;
 
 	node->uniq_verts = node->face_verts = 0;
 	totface = node->totprim;
@@ -294,6 +295,9 @@ static void build_mesh_leaf_node(PBVH *bvh, PBVHNode *node)
 			        map_insert_vert(bvh, map, &node->face_verts,
 			                        &node->uniq_verts, (&f->v1)[j]);
 		}
+
+		if(!paint_is_face_hidden(f, bvh->verts))
+			has_visible = true;
 	}
 
 	node->vert_indices = MEM_callocN(sizeof(int) *
@@ -331,6 +335,8 @@ static void build_mesh_leaf_node(PBVH *bvh, PBVHNode *node)
 
 	BKE_pbvh_node_mark_rebuild_draw(node);
 
+	BKE_pbvh_node_fully_hidden_set(node, !has_visible);
+
 	BLI_ghash_free(map, NULL, NULL);
 }
 
@@ -346,6 +352,45 @@ static void update_vb(PBVH *bvh, PBVHNode *node, BBC *prim_bbc,
 	node->orig_vb = node->vb;
 }
 
+/* Returns the number of visible quads in the nodes' grids. */
+int BKE_pbvh_count_grid_quads(BLI_bitmap **grid_hidden,
+								int *grid_indices, int totgrid,
+								int gridsize)
+{
+	int gridarea = (gridsize - 1) * (gridsize - 1);
+	int i, x, y, totquad;
+
+	/* grid hidden layer is present, so have to check each grid for
+	 * visibility */
+
+	for (i = 0, totquad = 0; i < totgrid; i++) {
+		const BLI_bitmap *gh = grid_hidden[grid_indices[i]];
+
+		if (gh) {
+			/* grid hidden are present, have to check each element */
+			for (y = 0; y < gridsize - 1; y++) {
+				for (x = 0; x < gridsize - 1; x++) {
+					if (!paint_is_grid_face_hidden(gh, gridsize, x, y))
+						totquad++;
+				}
+			}
+		}
+		else
+			totquad += gridarea;
+	}
+
+	return totquad;
+}
+
+static void build_grid_leaf_node(PBVH *bvh, PBVHNode *node)
+{
+	int totquads = BKE_pbvh_count_grid_quads(bvh->grid_hidden, node->prim_indices,
+											 node->totprim, bvh->gridkey.grid_size);
+	BKE_pbvh_node_fully_hidden_set(node, (totquads == 0));
+	BKE_pbvh_node_mark_rebuild_draw(node);
+}
+
+
 static void build_leaf(PBVH *bvh, int node_index, BBC *prim_bbc,
                        int offset, int count)
 {
@@ -359,8 +404,9 @@ static void build_leaf(PBVH *bvh, int node_index, BBC *prim_bbc,
 		
 	if (bvh->faces)
 		build_mesh_leaf_node(bvh, bvh->nodes + node_index);
-	else
+	else {
-		BKE_pbvh_node_mark_rebuild_draw(bvh->nodes + node_index);
+		build_grid_leaf_node(bvh, bvh->nodes + node_index);
+	}
 }
 
 /* Return zero if all primitives in the node can be drawn with the
@@ -1033,7 +1079,7 @@ static void pbvh_update_draw_buffers(PBVH *bvh, PBVHNode **nodes, int totnode)
 						GPU_build_grid_pbvh_buffers(node->prim_indices,
 					                           node->totprim,
 					                           bvh->grid_hidden,
-					                           bvh->gridkey.grid_size);
+											   bvh->gridkey.grid_size);
 					break;
 				case PBVH_FACES:
 					node->draw_buffers =

source/blender/blenkernel/intern/pbvh_bmesh.c

@@ -48,6 +48,7 @@ static void pbvh_bmesh_node_finalize(PBVH *bvh, int node_index, const int cd_ver
 {
 	GSetIterator gs_iter;
 	PBVHNode *n = &bvh->nodes[node_index];
+	bool has_visible = false;
 
 	/* Create vert hash sets */
 	n->bm_unique_verts = BLI_gset_ptr_new("bm_unique_verts");
@@ -80,6 +81,9 @@ static void pbvh_bmesh_node_finalize(PBVH *bvh, int node_index, const int cd_ver
 			/* Update node bounding box */
 			BB_expand(&n->vb, v->co);
 		} while ((l_iter = l_iter->next) != l_first);
+
+		if (!BM_elem_flag_test(f, BM_ELEM_HIDDEN))
+			has_visible = true;
 	}
 
 	BLI_assert(n->vb.bmin[0] <= n->vb.bmax[0] &&
@@ -90,6 +94,8 @@ static void pbvh_bmesh_node_finalize(PBVH *bvh, int node_index, const int cd_ver
 
 	/* Build GPU buffers for new node and update vertex normals */
 	BKE_pbvh_node_mark_rebuild_draw(n);
+
+	BKE_pbvh_node_fully_hidden_set(n, !has_visible);
 	n->flag |= PBVH_UpdateNormals;
 }
 

source/blender/gpu/intern/gpu_buffers.c

@@ -51,6 +51,7 @@
 #include "BKE_ccg.h"
 #include "BKE_DerivedMesh.h"
 #include "BKE_paint.h"
+#include "BKE_pbvh.h"
 
 #include "DNA_userdef_types.h"
 
@@ -1827,36 +1828,6 @@ void GPU_update_grid_pbvh_buffers(GPU_PBVH_Buffers *buffers, CCGElem **grids,
 	//printf("node updated %p\n", buffers);
 }
 
-/* Returns the number of visible quads in the nodes' grids. */
-static int gpu_count_grid_quads(BLI_bitmap **grid_hidden,
-                                int *grid_indices, int totgrid,
-                                int gridsize)
-{
-	int gridarea = (gridsize - 1) * (gridsize - 1);
-	int i, x, y, totquad;
-
-	/* grid hidden layer is present, so have to check each grid for
-	 * visibility */
-
-	for (i = 0, totquad = 0; i < totgrid; i++) {
-		const BLI_bitmap *gh = grid_hidden[grid_indices[i]];
-
-		if (gh) {
-			/* grid hidden are present, have to check each element */
-			for (y = 0; y < gridsize - 1; y++) {
-				for (x = 0; x < gridsize - 1; x++) {
-					if (!paint_is_grid_face_hidden(gh, gridsize, x, y))
-						totquad++;
-				}
-			}
-		}
-		else
-			totquad += gridarea;
-	}
-
-	return totquad;
-}
-
 /* Build the element array buffer of grid indices using either
  * unsigned shorts or unsigned ints. */
 #define FILL_QUAD_BUFFER(type_, tot_quad_, buffer_)                     \
@@ -1960,7 +1931,7 @@ static GLuint gpu_get_grid_buffer(int gridsize, GLenum *index_type, unsigned *to
 }
 
 GPU_PBVH_Buffers *GPU_build_grid_pbvh_buffers(int *grid_indices, int totgrid,
-                                              BLI_bitmap **grid_hidden, int gridsize)
+											  BLI_bitmap **grid_hidden, int gridsize)
 {
 	GPU_PBVH_Buffers *buffers;
 	int totquad;
@@ -1974,7 +1945,7 @@ GPU_PBVH_Buffers *GPU_build_grid_pbvh_buffers(int *grid_indices, int totgrid,
 	buffers->use_matcaps = false;
 
 	/* Count the number of quads */
-	totquad = gpu_count_grid_quads(grid_hidden, grid_indices, totgrid, gridsize);
+	totquad = BKE_pbvh_count_grid_quads(grid_hidden, grid_indices, totgrid, gridsize);
 
 	/* totally hidden node, return here to avoid BufferData with zero below. */
 	if (totquad == 0)