Add dynamic topology support to sculpt mode

* User documentation:
  wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.66/Dynamic_Topology_Sculpting

* Code review for this and the other dynamic-topology commits:
  https://codereview.appspot.com/6947064/
  Thanks to Sergey for doing code review!

* Add SCULPT_OT_dynamic_topology_toggle operator to enable or disable
  dynamic topology mode

* Most brushes need little modification for dynamic topology, but for
  some it won't work well and is disabled. This decision is made in
  sculpt_stroke_dynamic_topology().

* For brushes that need original data (e.g. grab brush) the topology
  is not updated during the stroke, but some changes to original
  vertex data is accessed were made since BMesh works a little
  differently from mesh/multires. This is abstracted with
  SculptOrigVertData and associated functions.

* Smooth brush gets yet another set of functions, for mesh and
  multires and dynamic topology and, separetely, masking

* For most brushes, the topology is updated during the stroke right
  before the regular brush action takes place. This is handled in
  sculpt_topology_update().

* Exiting sculpt mode also disables dynamic topology

* Sculpt undo works differently with BMesh. Since the contents of
  nodes in the PBVH do not remain static during a sculpt session, the
  SculptUndoNodes do not correspond with PBVHNodes if dynamic topology
  is enabled. Rather, each SculptUndoNode is associated with a
  BMLogEntry.

* Sculpt undo gets a few new cases: entering and exiting dynamic
  topology does an undo push of all mesh data. Symmetrize will
  similarly push a full copy of BMesh data, although it does so
  through the BMLog API.

* Undo and redo in dynamic-topology mode will do a full recalculation
  of the PBVH.

* Add some documentation to doc/sculpt.org. This could stand to be
  expanded a lot more, for now it mostly contains test cases for the
  undo system.

* Add SCULPT_OT_optimize operator to recalculate the BVH. The BVH gets
  less optimal more quickly with dynamic topology than regular
  sculpting. There is no doubt more clever stuff we can do to optimize
  it on the fly, but for now this gives the user a nicer way to
  recalculate it than toggling modes.

3 files changed, 920 insertions, 93 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 2f0d69bfd98..12843fde852 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -65,6 +65,7 @@
 #include "BKE_report.h"
 #include "BKE_lattice.h" /* for armature_deform_verts */
 #include "BKE_node.h"
+#include "BKE_object.h"
 #include "BKE_subsurf.h"
 
 #include "BIF_glutil.h"
@@ -86,6 +87,8 @@
 
 #include "GPU_buffers.h"
 
+#include "bmesh.h"
+
 #include <math.h>
 #include <stdlib.h>
 #include <string.h>
@@ -98,8 +101,13 @@ void ED_sculpt_force_update(bContext *C)
 {
 	Object *ob = CTX_data_active_object(C);
 
-	if (ob && (ob->mode & OB_MODE_SCULPT))
+	if (ob && (ob->mode & OB_MODE_SCULPT)) {
 		multires_force_update(ob);
+
+		/* Set reorder=false so that saving the file doesn't reorder
+		 * the BMesh's elements */
+		sculptsession_bm_to_me(ob, FALSE);
+	}
 }
 
 float *ED_sculpt_get_last_stroke(struct Object *ob)
@@ -172,7 +180,8 @@ static int sculpt_modifiers_active(Scene *scene, Sculpt *sd, Object *ob)
 	Mesh *me = (Mesh *)ob->data;
 	MultiresModifierData *mmd = sculpt_multires_active(scene, ob);
 
-	if (mmd) return 0;
+	if (mmd || ob->sculpt->bm)
+		return 0;
 
 	/* non-locked shape keys could be handled in the same way as deformed mesh */
 	if ((ob->shapeflag & OB_SHAPE_LOCK) == 0 && me->key && ob->shapenr)
@@ -281,12 +290,130 @@ typedef struct StrokeCache {
 	rcti previous_r; /* previous redraw rectangle */
 } StrokeCache;
 
+/************** Access to original unmodified vertex data *************/
+
+typedef struct {
+	BMLog *bm_log;
+
+	SculptUndoNode *unode;
+	float (*coords)[3];
+	short (*normals)[3];
+	float *vmasks;
+
+	/* Original coordinate, normal, and mask */
+	const float *co;
+	float mask;
+	short no[3];
+} SculptOrigVertData;
+
+
+/* Initialize a SculptOrigVertData for accessing original vertex data;
+ * handles BMesh, mesh, and multires */
+static void sculpt_orig_vert_data_unode_init(SculptOrigVertData *data,
+											 Object *ob,
+											 SculptUndoNode *unode)
+{
+	SculptSession *ss = ob->sculpt;
+	BMesh *bm = ss->bm;
+
+	memset(data, 0, sizeof(*data));
+	data->unode = unode;
+
+	if (bm) {
+		data->bm_log = ss->bm_log;
+	}
+	else {
+		data->coords = data->unode->co;
+		data->normals = data->unode->no;
+		data->vmasks = data->unode->mask;
+	}
+}
+
+/* Initialize a SculptOrigVertData for accessing original vertex data;
+ * handles BMesh, mesh, and multires */
+static void sculpt_orig_vert_data_init(SculptOrigVertData *data,
+									   Object *ob,
+									   PBVHNode *node)
+{
+	SculptUndoNode *unode;
+	unode = sculpt_undo_push_node(ob, node, SCULPT_UNDO_COORDS);
+	sculpt_orig_vert_data_unode_init(data, ob, unode);
+									 
+}
+
+/* Update a SculptOrigVertData for a particular vertex from the PBVH
+ * iterator */
+static void sculpt_orig_vert_data_update(SculptOrigVertData *orig_data,
+										 PBVHVertexIter *iter)
+{
+	if (orig_data->unode->type == SCULPT_UNDO_COORDS) {
+		if (orig_data->coords) {
+			orig_data->co = orig_data->coords[iter->i];
+		}
+		else {
+			orig_data->co = BM_log_original_vert_co(orig_data->bm_log, iter->bm_vert);
+		}
+
+		if (orig_data->normals) {
+			copy_v3_v3_short(orig_data->no, orig_data->normals[iter->i]);
+		}
+		else {
+			/* TODO: log doesn't store normals yet */
+			normal_float_to_short_v3(orig_data->no, iter->bm_vert->no);
+		}
+	}
+	else if (orig_data->unode->type == SCULPT_UNDO_MASK) {
+		if (orig_data->vmasks) {
+			orig_data->mask = orig_data->vmasks[iter->i];
+		}
+		else {
+			orig_data->mask = BM_log_original_mask(orig_data->bm_log, iter->bm_vert);
+		}
+	}
+}
+
+/**********************************************************************/
+
+/* Returns true if the stroke will use dynamic topology, false
+   otherwise.
+
+   Factors: some brushes like grab cannot do dynamic topology.
+   Others, like smooth, are better without. Same goes for alt-
+   key smoothing. */
+static int sculpt_stroke_dynamic_topology(const SculptSession *ss,
+										  const Brush *brush)
+{
+	return ((BLI_pbvh_type(ss->pbvh) == PBVH_BMESH) &&
+
+			(!ss->cache || (!ss->cache->alt_smooth)) &&
+
+			/* Requires mesh restore, which doesn't work with
+			 * dynamic-topology */
+			!(brush->flag & BRUSH_ANCHORED) &&
+			!(brush->flag & BRUSH_RESTORE_MESH) &&
+
+			(!ELEM6(brush->sculpt_tool,
+					/* These brushes, as currently coded, cannot
+					 * support dynamic topology */
+					SCULPT_TOOL_GRAB,
+					SCULPT_TOOL_ROTATE,
+					SCULPT_TOOL_THUMB,
+					SCULPT_TOOL_LAYER,
+
+					/* These brushes could handle dynamic topology,
+					 * but user feedback indicates it's better not
+					 * to */
+					SCULPT_TOOL_SMOOTH,
+					SCULPT_TOOL_MASK)));
+}
 
 /*** paint mesh ***/
 
-static void paint_mesh_restore_co(Sculpt *sd, SculptSession *ss)
+static void paint_mesh_restore_co(Sculpt *sd, Object *ob)
 {
+	SculptSession *ss = ob->sculpt;
 	StrokeCache *cache = ss->cache;
+	const Brush *brush = paint_brush(&sd->paint);
 	int i;
 
 	PBVHNode **nodes;
@@ -301,20 +428,27 @@ static void paint_mesh_restore_co(Sculpt *sd, SculptSession *ss)
 	#pragma omp parallel for schedule(guided) if (sd->flags & SCULPT_USE_OPENMP)
 	for (n = 0; n < totnode; n++) {
 		SculptUndoNode *unode;
-		
-		unode = sculpt_undo_get_node(nodes[n]);
+		SculptUndoType type = (brush->sculpt_tool == SCULPT_TOOL_MASK ?
+							   SCULPT_UNDO_MASK : SCULPT_UNDO_COORDS);
+
+		unode = sculpt_undo_push_node(ob, nodes[n], type);
 		if (unode) {
 			PBVHVertexIter vd;
+			SculptOrigVertData orig_data;
 
+			sculpt_orig_vert_data_unode_init(&orig_data, ob, unode);
+		
 			BLI_pbvh_vertex_iter_begin(ss->pbvh, nodes[n], vd, PBVH_ITER_UNIQUE)
 			{
-				if (unode->type == SCULPT_UNDO_COORDS) {
-					copy_v3_v3(vd.co, unode->co[vd.i]);
-					if (vd.no) copy_v3_v3_short(vd.no, unode->no[vd.i]);
-					else normal_short_to_float_v3(vd.fno, unode->no[vd.i]);
+				sculpt_orig_vert_data_update(&orig_data, &vd);
+
+				if (orig_data.unode->type == SCULPT_UNDO_COORDS) {
+					copy_v3_v3(vd.co, orig_data.co);
+					if (vd.no) copy_v3_v3_short(vd.no, orig_data.no);
+					else normal_short_to_float_v3(vd.fno, orig_data.no);
 				}
-				else if (unode->type == SCULPT_UNDO_MASK) {
-					*vd.mask = unode->mask[vd.i];
+				else if (orig_data.unode->type == SCULPT_UNDO_MASK) {
+					*vd.mask = orig_data.mask;
 				}
 				if (vd.mvert) vd.mvert->flag |= ME_VERT_PBVH_UPDATE;
 			}
@@ -405,7 +539,7 @@ static void sculpt_brush_test_init(SculptSession *ss, SculptBrushTest *test)
 	test->dist = 0.0f;   /* just for initialize */
 }
 
-static int sculpt_brush_test(SculptBrushTest *test, float co[3])
+static int sculpt_brush_test(SculptBrushTest *test, const float co[3])
 {
 	float distsq = len_squared_v3v3(co, test->location);
 
@@ -418,7 +552,7 @@ static int sculpt_brush_test(SculptBrushTest *test, float co[3])
 	}
 }
 
-static int sculpt_brush_test_sq(SculptBrushTest *test, float co[3])
+static int sculpt_brush_test_sq(SculptBrushTest *test, const float co[3])
 {
 	float distsq = len_squared_v3v3(co, test->location);
 
@@ -734,7 +868,8 @@ static float brush_strength(Sculpt *sd, StrokeCache *cache, float feather)
 }
 
 /* Return a multiplier for brush strength on a particular vertex. */
-static float tex_strength(SculptSession *ss, Brush *br, float point[3],
+static float tex_strength(SculptSession *ss, Brush *br,
+						  const float point[3],
                           const float len,
                           const float sculpt_normal[3],
                           const short vno[3],
@@ -926,6 +1061,11 @@ static void calc_area_normal(Sculpt *sd, Object *ob, float an[3], PBVHNode **nod
 	original = (paint_brush(&sd->paint)->sculpt_tool == SCULPT_TOOL_GRAB ?
 	            TRUE : ss->cache->original);
 
+	/* In general the original coords are not available with dynamic
+	 * topology */
+	if (ss->bm)
+		original = FALSE;
+
 	(void)sd; /* unused w/o openmp */
 	
 	zero_v3(an);
@@ -1210,6 +1350,81 @@ static float neighbor_average_mask(SculptSession *ss, unsigned vert)
 		return vmask[vert];
 }
 
+/* Same logic as neighbor_average(), but for bmesh rather than mesh */
+static void bmesh_neighbor_average(float avg[3], BMVert *v)
+{
+	int vfcount = BM_vert_face_count(v);
+
+	zero_v3(avg);
+		
+	/* Don't modify corner vertices */
+	if (vfcount > 1) {
+		BMIter iter;
+		BMFace *f;
+		int i, total = 0;
+
+		BM_ITER_ELEM (f, &iter, v, BM_FACES_OF_VERT) {
+			BMLoop *l1 = BM_face_vert_share_loop(f, v);
+			BMLoop *l2 = BM_loop_other_vert_loop(l1, v);
+			BMVert *adj_v[3] = {
+				BM_edge_other_vert(l1->e, v),
+				v,
+				BM_edge_other_vert(l2->e, v)};
+			
+			for (i = 0; i < 3; i++) {
+				if (vfcount != 2 || BM_vert_face_count(adj_v[i]) <= 2) {
+					add_v3_v3(avg, adj_v[i]->co);
+					total++;
+				}
+			}
+		}
+
+		if (total > 0) {
+			mul_v3_fl(avg, 1.0f / total);
+			return;
+		}
+	}
+
+	copy_v3_v3(avg, v->co);
+}
+
+/* Same logic as neighbor_average_mask(), but for bmesh rather than mesh */
+static float bmesh_neighbor_average_mask(BMesh *bm, BMVert *v)
+{
+	BMIter iter;
+	BMFace *f;
+	float avg = 0;
+	int i, total = 0;
+
+	BM_ITER_ELEM (f, &iter, v, BM_FACES_OF_VERT) {
+		BMLoop *l1 = BM_face_vert_share_loop(f, v);
+		BMLoop *l2 = BM_loop_other_vert_loop(l1, v);
+		BMVert *adj_v[3] = {
+			BM_edge_other_vert(l1->e, v),
+			v,
+			BM_edge_other_vert(l2->e, v)};
+			
+		for (i = 0; i < 3; i++) {
+			BMVert *v2 = adj_v[i];
+			float *vmask = CustomData_bmesh_get(&bm->vdata,
+												v2->head.data,
+												CD_PAINT_MASK);
+			avg += (*vmask);
+			total++;
+		}
+	}
+
+	if (total > 0) {
+		return avg / (float)total;
+	}
+	else {
+		float *vmask = CustomData_bmesh_get(&bm->vdata,
+											v->head.data,
+											CD_PAINT_MASK);
+		return (*vmask);
+	}
+}
+
 static void do_mesh_smooth_brush(Sculpt *sd, SculptSession *ss, PBVHNode *node, float bstrength, int smooth_mask)
 {
 	Brush *brush = paint_brush(&sd->paint);
@@ -1251,6 +1466,47 @@ static void do_mesh_smooth_brush(Sculpt *sd, SculptSession *ss, PBVHNode *node,
 	BLI_pbvh_vertex_iter_end;
 }
 
+static void do_bmesh_smooth_brush(Sculpt *sd, SculptSession *ss, PBVHNode *node, float bstrength, int smooth_mask)
+{
+	Brush *brush = paint_brush(&sd->paint);
+	PBVHVertexIter vd;
+	SculptBrushTest test;
+	
+	CLAMP(bstrength, 0.0f, 1.0f);
+
+	sculpt_brush_test_init(ss, &test);
+
+	BLI_pbvh_vertex_iter_begin(ss->pbvh, node, vd, PBVH_ITER_UNIQUE)
+	{
+		if (sculpt_brush_test(&test, vd.co)) {
+			const float fade = bstrength * tex_strength(ss, brush, vd.co, test.dist,
+			                                            ss->cache->view_normal, vd.no, vd.fno,
+			                                            smooth_mask ? 0 : *vd.mask);
+			if (smooth_mask) {
+				float val = bmesh_neighbor_average_mask(ss->bm, vd.bm_vert) - *vd.mask;
+				val *= fade * bstrength;
+				*vd.mask += val;
+				CLAMP(*vd.mask, 0, 1);
+			}
+			else {
+				float avg[3], val[3];
+
+				bmesh_neighbor_average(avg, vd.bm_vert);
+				sub_v3_v3v3(val, avg, vd.co);
+				mul_v3_fl(val, fade);
+
+				add_v3_v3(val, vd.co);
+
+				sculpt_clip(sd, ss, vd.co, val);
+			}
+
+			if (vd.mvert)
+				vd.mvert->flag |= ME_VERT_PBVH_UPDATE;
+		}
+	}
+	BLI_pbvh_vertex_iter_end;
+}
+
 static void do_multires_smooth_brush(Sculpt *sd, SculptSession *ss, PBVHNode *node,
                                      float bstrength, int smooth_mask)
 {
@@ -1433,6 +1689,9 @@ static void smooth(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode,
 					do_mesh_smooth_brush(sd, ss, nodes[n], strength,
 					                     smooth_mask);
 					break;
+				case PBVH_BMESH:
+					do_bmesh_smooth_brush(sd, ss, nodes[n], strength, smooth_mask);
+					break;
 			}
 		}
 
@@ -1659,15 +1918,11 @@ static void do_grab_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode)
 	#pragma omp parallel for schedule(guided) if (sd->flags & SCULPT_USE_OPENMP)
 	for (n = 0; n < totnode; n++) {
 		PBVHVertexIter vd;
-		SculptUndoNode *unode;
 		SculptBrushTest test;
-		float (*origco)[3];
-		short (*origno)[3];
+		SculptOrigVertData orig_data;
 		float (*proxy)[3];
 
-		unode =  sculpt_undo_push_node(ob, nodes[n], SCULPT_UNDO_COORDS);
-		origco = unode->co;
-		origno = unode->no;
+		sculpt_orig_vert_data_init(&orig_data, ob, nodes[n]);
 
 		proxy = BLI_pbvh_node_add_proxy(ss->pbvh, nodes[n])->co;
 
@@ -1675,10 +1930,15 @@ static void do_grab_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode)
 
 		BLI_pbvh_vertex_iter_begin(ss->pbvh, nodes[n], vd, PBVH_ITER_UNIQUE)
 		{
-			if (sculpt_brush_test(&test, origco[vd.i])) {
-				const float fade = bstrength * tex_strength(ss, brush, origco[vd.i], test.dist,
-				                                            ss->cache->sculpt_normal_symm, origno[vd.i],
-				                                            NULL, vd.mask ? *vd.mask : 0.0f);
+			sculpt_orig_vert_data_update(&orig_data, &vd);
+
+			if (sculpt_brush_test(&test, orig_data.co)) {
+				const float fade = bstrength * tex_strength(ss, brush,
+															orig_data.co,
+															test.dist,
+				                                            ss->cache->sculpt_normal_symm,
+															orig_data.no,
+															NULL, vd.mask ? *vd.mask : 0.0f);
 
 				mul_v3_v3fl(proxy[vd.i], grab_delta, fade);
 
@@ -1797,15 +2057,11 @@ static void do_thumb_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode
 	#pragma omp parallel for schedule(guided) if (sd->flags & SCULPT_USE_OPENMP)
 	for (n = 0; n < totnode; n++) {
 		PBVHVertexIter vd;
-		SculptUndoNode *unode;
 		SculptBrushTest test;
-		float (*origco)[3];
-		short (*origno)[3];
+		SculptOrigVertData orig_data;
 		float (*proxy)[3];
 
-		unode =  sculpt_undo_push_node(ob, nodes[n], SCULPT_UNDO_COORDS);
-		origco = unode->co;
-		origno = unode->no;
+		sculpt_orig_vert_data_init(&orig_data, ob, nodes[n]);
 
 		proxy = BLI_pbvh_node_add_proxy(ss->pbvh, nodes[n])->co;
 
@@ -1813,10 +2069,15 @@ static void do_thumb_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode
 
 		BLI_pbvh_vertex_iter_begin(ss->pbvh, nodes[n], vd, PBVH_ITER_UNIQUE)
 		{
-			if (sculpt_brush_test(&test, origco[vd.i])) {
-				const float fade = bstrength * tex_strength(ss, brush, origco[vd.i], test.dist,
+			sculpt_orig_vert_data_update(&orig_data, &vd);
+
+			if (sculpt_brush_test(&test, orig_data.co)) {
+				const float fade = bstrength * tex_strength(ss, brush,
+															orig_data.co,
+															test.dist,
 				                                            ss->cache->sculpt_normal_symm,
-				                                            origno[vd.i], NULL, vd.mask ? *vd.mask : 0.0f);
+				                                            orig_data.no,
+															NULL, vd.mask ? *vd.mask : 0.0f);
 
 				mul_v3_v3fl(proxy[vd.i], cono, fade);
 
@@ -1850,15 +2111,11 @@ static void do_rotate_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnod
 	#pragma omp parallel for schedule(guided) if (sd->flags & SCULPT_USE_OPENMP)
 	for (n = 0; n < totnode; n++) {
 		PBVHVertexIter vd;
-		SculptUndoNode *unode;
 		SculptBrushTest test;
-		float (*origco)[3];
-		short (*origno)[3];
+		SculptOrigVertData orig_data;
 		float (*proxy)[3];
 
-		unode =  sculpt_undo_push_node(ob, nodes[n], SCULPT_UNDO_COORDS);
-		origco = unode->co;
-		origno = unode->no;
+		sculpt_orig_vert_data_init(&orig_data, ob, nodes[n]);
 
 		proxy = BLI_pbvh_node_add_proxy(ss->pbvh, nodes[n])->co;
 
@@ -1866,13 +2123,18 @@ static void do_rotate_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnod
 
 		BLI_pbvh_vertex_iter_begin(ss->pbvh, nodes[n], vd, PBVH_ITER_UNIQUE)
 		{
-			if (sculpt_brush_test(&test, origco[vd.i])) {
-				const float fade = bstrength * tex_strength(ss, brush, origco[vd.i], test.dist,
+			sculpt_orig_vert_data_update(&orig_data, &vd);
+
+			if (sculpt_brush_test(&test, orig_data.co)) {
+				const float fade = bstrength * tex_strength(ss, brush,
+				                                            orig_data.co,
+				                                            test.dist,
 				                                            ss->cache->sculpt_normal_symm,
-				                                            origno[vd.i], NULL, vd.mask ? *vd.mask : 0.0f);
+				                                            orig_data.no,
+		                                                    NULL, vd.mask ? *vd.mask : 0.0f);
 
-				mul_v3_m4v3(proxy[vd.i], m, origco[vd.i]);
-				sub_v3_v3(proxy[vd.i], origco[vd.i]);
+				mul_v3_m4v3(proxy[vd.i], m, orig_data.co);
+				sub_v3_v3(proxy[vd.i], orig_data.co);
 				mul_v3_fl(proxy[vd.i], fade);
 
 				if (vd.mvert)
@@ -1901,13 +2163,12 @@ static void do_layer_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode
 	for (n = 0; n < totnode; n++) {
 		PBVHVertexIter vd;
 		SculptBrushTest test;
-		SculptUndoNode *unode;
-		float (*origco)[3], *layer_disp;
+		SculptOrigVertData orig_data;
+		float *layer_disp;
 		/* XXX: layer brush needs conversion to proxy but its more complicated */
 		/* proxy = BLI_pbvh_node_add_proxy(ss->pbvh, nodes[n])->co; */
 		
-		unode = sculpt_undo_push_node(ob, nodes[n], SCULPT_UNDO_COORDS);
-		origco = unode->co;
+		sculpt_orig_vert_data_init(&orig_data, ob, nodes[n]);
 
 		#pragma omp critical
 		{
@@ -1918,7 +2179,9 @@ static void do_layer_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode
 
 		BLI_pbvh_vertex_iter_begin(ss->pbvh, nodes[n], vd, PBVH_ITER_UNIQUE)
 		{
-			if (sculpt_brush_test(&test, origco[vd.i])) {
+			sculpt_orig_vert_data_update(&orig_data, &vd);
+
+			if (sculpt_brush_test(&test, orig_data.co)) {
 				const float fade = bstrength * tex_strength(ss, brush, vd.co, test.dist,
 				                                            ss->cache->sculpt_normal_symm,
 				                                            vd.no, vd.fno, vd.mask ? *vd.mask : 0.0f);
@@ -1940,7 +2203,7 @@ static void do_layer_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode
 					add_v3_v3(val, ss->layer_co[index]);
 				}
 				else {
-					add_v3_v3(val, origco[vd.i]);
+					add_v3_v3(val, orig_data.co);
 				}
 
 				sculpt_clip(sd, ss, vd.co, val);
@@ -2081,7 +2344,7 @@ static void calc_area_normal_and_flatten_center(Sculpt *sd, Object *ob,
 		unode = sculpt_undo_push_node(ob, nodes[n], SCULPT_UNDO_COORDS);
 		sculpt_brush_test_init(ss, &test);
 
-		if (ss->cache->original) {
+		if (ss->cache->original && unode->co) {
 			BLI_pbvh_vertex_iter_begin(ss->pbvh, nodes[n], vd, PBVH_ITER_UNIQUE)
 			{
 				if (sculpt_brush_test_fast(&test, unode->co[vd.i])) {
@@ -2687,6 +2950,63 @@ void sculpt_vertcos_to_key(Object *ob, KeyBlock *kb, float (*vertCos)[3])
 	BKE_key_convert_from_vertcos(ob, kb, vertCos);
 }
 
+/* Note: we do the topology update before any brush actions to avoid
+ * issues with the proxies. The size of the proxy can't change, so
+ * topology must be updated first. */
+static void sculpt_topology_update(Sculpt *sd, Object *ob, Brush *brush)
+{
+	SculptSession *ss = ob->sculpt;
+	SculptSearchSphereData data;
+	PBVHNode **nodes = NULL;
+	float radius;
+	int n, totnode;
+
+	/* Build a list of all nodes that are potentially within the
+	 * brush's area of influence */
+	data.ss = ss;
+	data.sd = sd;
+
+	radius = ss->cache->radius * 1.25;
+
+	data.radius_squared = radius * radius;
+	data.original = ELEM4(brush->sculpt_tool,
+	                      SCULPT_TOOL_GRAB,
+	                      SCULPT_TOOL_ROTATE,
+	                      SCULPT_TOOL_THUMB,
+	                      SCULPT_TOOL_LAYER);
+
+	BLI_pbvh_search_gather(ss->pbvh, sculpt_search_sphere_cb, &data, &nodes, &totnode);
+
+	/* Only act if some verts are inside the brush area */
+	if (totnode) {
+		PBVHTopologyUpdateMode mode = PBVH_Subdivide;
+
+		if (sd->flags & SCULPT_DYNTOPO_COLLAPSE) {
+			mode |= PBVH_Collapse;
+		}
+
+		for (n = 0; n < totnode; n++) {
+			sculpt_undo_push_node(ob, nodes[n],
+			                      brush->sculpt_tool == SCULPT_TOOL_MASK ?
+			                      SCULPT_UNDO_MASK : SCULPT_UNDO_COORDS);
+			BLI_pbvh_node_mark_update(nodes[n]);
+
+			if (BLI_pbvh_type(ss->pbvh) == PBVH_BMESH) {
+				BLI_pbvh_node_mark_topology_update(nodes[n]);
+				BLI_pbvh_bmesh_node_save_orig(nodes[n]);
+			}
+		}
+
+		if (BLI_pbvh_type(ss->pbvh) == PBVH_BMESH) {
+			BLI_pbvh_bmesh_update_topology(ss->pbvh, mode,
+										   ss->cache->location,
+			                               ss->cache->radius);
+		}
+
+		MEM_freeN(nodes);
+	}
+}
+
 static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush)
 {
 	SculptSession *ss = ob->sculpt;
@@ -2834,7 +3154,7 @@ static void sculpt_combine_proxies(Sculpt *sd, Object *ob)
 			int proxy_count;
 			float (*orco)[3];
 
-			if (use_orco)
+			if (use_orco && !ss->bm)
 				orco = sculpt_undo_push_node(ob, nodes[n], SCULPT_UNDO_COORDS)->co;
 
 			BLI_pbvh_node_get_proxies(nodes[n], &proxies, &proxy_count);
@@ -2844,8 +3164,15 @@ static void sculpt_combine_proxies(Sculpt *sd, Object *ob)
 				float val[3];
 				int p;
 
-				if (use_orco)
-					copy_v3_v3(val, orco[vd.i]);
+				if (use_orco) {
+					if (ss->bm) {
+						copy_v3_v3(val,
+								   BM_log_original_vert_co(ss->bm_log,
+								   vd.bm_vert));
+					}
+					else
+						copy_v3_v3(val, orco[vd.i]);
+				}
 				else
 					copy_v3_v3(val, vd.co);
 
@@ -2977,7 +3304,10 @@ static void calc_brushdata_symm(Sculpt *sd, StrokeCache *cache, const char symm,
 	mul_m4_v3(cache->symm_rot_mat, cache->grab_delta_symmetry);
 }
 
+typedef void (*BrushActionFunc)(Sculpt *sd, Object *ob, Brush *brush);
+
 static void do_radial_symmetry(Sculpt *sd, Object *ob, Brush *brush,
+							   BrushActionFunc action,
                                const char symm, const int axis,
                                const float feather)
 {
@@ -2988,7 +3318,7 @@ static void do_radial_symmetry(Sculpt *sd, Object *ob, Brush *brush,
 		const float angle = 2 * M_PI * i / sd->radial_symm[axis - 'X'];
 		ss->cache->radial_symmetry_pass = i;
 		calc_brushdata_symm(sd, ss->cache, symm, axis, angle, feather);
-		do_brush_action(sd, ob, brush);
+		action(sd, ob, brush);
 	}
 }
 
@@ -3005,7 +3335,8 @@ static void sculpt_fix_noise_tear(Sculpt *sd, Object *ob)
 		multires_stitch_grids(ob);
 }
 
-static void do_symmetrical_brush_actions(Sculpt *sd, Object *ob)
+static void do_symmetrical_brush_actions(Sculpt *sd, Object *ob,
+										 BrushActionFunc action)
 {
 	Brush *brush = paint_brush(&sd->paint);
 	SculptSession *ss = ob->sculpt;
@@ -3016,7 +3347,6 @@ static void do_symmetrical_brush_actions(Sculpt *sd, Object *ob)
 	float feather = calc_symmetry_feather(sd, ss->cache);
 
 	cache->bstrength = brush_strength(sd, cache, feather);
-
 	cache->symmetry = symm;
 
 	/* symm is a bit combination of XYZ - 1 is mirror X; 2 is Y; 3 is XY; 4 is Z; 5 is XZ; 6 is YZ; 7 is XYZ */ 
@@ -3026,23 +3356,13 @@ static void do_symmetrical_brush_actions(Sculpt *sd, Object *ob)
 			cache->radial_symmetry_pass = 0;
 
 			calc_brushdata_symm(sd, cache, i, 0, 0, feather);
-			do_brush_action(sd, ob, brush);
+			action(sd, ob, brush);
 
-			do_radial_symmetry(sd, ob, brush, i, 'X', feather);
-			do_radial_symmetry(sd, ob, brush, i, 'Y', feather);
-			do_radial_symmetry(sd, ob, brush, i, 'Z', feather);
+			do_radial_symmetry(sd, ob, brush, action, i, 'X', feather);
+			do_radial_symmetry(sd, ob, brush, action, i, 'Y', feather);
+			do_radial_symmetry(sd, ob, brush, action, i, 'Z', feather);
 		}
 	}
-
-	sculpt_combine_proxies(sd, ob);
-
-	/* hack to fix noise texture tearing mesh */
-	sculpt_fix_noise_tear(sd, ob);
-
-	if (ss->modifiers_active)
-		sculpt_flush_stroke_deform(sd, ob);
-
-	cache->first_time = 0;
 }
 
 static void sculpt_update_tex(const Scene *scene, Sculpt *sd, SculptSession *ss)
@@ -3405,8 +3725,9 @@ static void sculpt_update_cache_invariants(bContext *C, Sculpt *sd, SculptSessio
 	ED_view3d_global_to_vector(cache->vc->rv3d, cache->vc->rv3d->twmat[3], cache->true_view_normal);
 	/* Initialize layer brush displacements and persistent coords */
 	if (brush->sculpt_tool == SCULPT_TOOL_LAYER) {
-		/* not supported yet for multires */
-		if (!ss->multires && !ss->layer_co && (brush->flag & BRUSH_PERSISTENT)) {
+		/* not supported yet for multires or dynamic topology */
+		if (!ss->multires && !ss->bm && !ss->layer_co &&
+			(brush->flag & BRUSH_PERSISTENT)) {
 			if (!ss->layer_co)
 				ss->layer_co = MEM_mallocN(sizeof(float) * 3 * ss->totvert,
 				                           "sculpt mesh vertices copy");
@@ -3723,14 +4044,23 @@ static void sculpt_raycast_cb(PBVHNode *node, void *data_v, float *tmin)
 	if (BLI_pbvh_node_get_tmin(node) < *tmin) {
 		SculptRaycastData *srd = data_v;
 		float (*origco)[3] = NULL;
+		int use_origco = FALSE;
 
 		if (srd->original && srd->ss->cache) {
-			/* intersect with coordinates from before we started stroke */
-			SculptUndoNode *unode = sculpt_undo_get_node(node);
-			origco = (unode) ? unode->co : NULL;
+			if (BLI_pbvh_type(srd->ss->pbvh) == PBVH_BMESH) {
+				use_origco = TRUE;
+			}
+			else {
+				/* intersect with coordinates from before we started stroke */
+				SculptUndoNode *unode = sculpt_undo_get_node(node);
+				origco = (unode) ? unode->co : NULL;
+				use_origco = origco ? TRUE : FALSE;
+			}
 		}
 
-		if (BLI_pbvh_node_raycast(srd->ss->pbvh, node, origco, srd->ray_start, srd->ray_normal, &srd->dist)) {
+		if (BLI_pbvh_node_raycast(srd->ss->pbvh, node, origco, use_origco,
+								  srd->ray_start, srd->ray_normal, &srd->dist))
+		{
 			srd->hit = 1;
 			*tmin = srd->dist;
 		}
@@ -3828,8 +4158,9 @@ static int sculpt_brush_stroke_init(bContext *C, wmOperator *op)
 	return 1;
 }
 
-static void sculpt_restore_mesh(Sculpt *sd, SculptSession *ss)
+static void sculpt_restore_mesh(Sculpt *sd, Object *ob)
 {
+	SculptSession *ss = ob->sculpt;
 	Brush *brush = paint_brush(&sd->paint);
 
 	/* Restore the mesh before continuing with anchored stroke */
@@ -3838,7 +4169,7 @@ static void sculpt_restore_mesh(Sculpt *sd, SculptSession *ss)
 	     BKE_brush_use_size_pressure(ss->cache->vc->scene, brush)) ||
 	    (brush->flag & BRUSH_RESTORE_MESH))
 	{
-		paint_mesh_restore_co(sd, ss);
+		paint_mesh_restore_co(sd, ob);
 	}
 }
 
@@ -3916,11 +4247,32 @@ static void sculpt_stroke_update_step(bContext *C, struct PaintStroke *stroke, P
 	Sculpt *sd = CTX_data_tool_settings(C)->sculpt;
 	Object *ob = CTX_data_active_object(C);
 	SculptSession *ss = ob->sculpt;
+	const Brush *brush = paint_brush(&sd->paint);
 	
 	sculpt_stroke_modifiers_check(C, ob);
 	sculpt_update_cache_variants(C, sd, ob, stroke, itemptr);
-	sculpt_restore_mesh(sd, ss);
-	do_symmetrical_brush_actions(sd, ob);
+	sculpt_restore_mesh(sd, ob);
+
+	BLI_pbvh_bmesh_detail_size_set(ss->pbvh,
+								   (ss->cache->radius /
+									(float)ss->cache->pixel_radius) *
+								   (float)sd->detail_size);
+
+	if (sculpt_stroke_dynamic_topology(ss, brush)) {
+		do_symmetrical_brush_actions(sd, ob, sculpt_topology_update);
+	}
+
+	do_symmetrical_brush_actions(sd, ob, do_brush_action);
+
+	sculpt_combine_proxies(sd, ob);
+
+	/* hack to fix noise texture tearing mesh */
+	sculpt_fix_noise_tear(sd, ob);
+
+	if (ss->modifiers_active)
+		sculpt_flush_stroke_deform(sd, ob);
+
+	ss->cache->first_time = FALSE;
 
 	/* Cleanup */
 	sculpt_flush_update(C);
@@ -3980,6 +4332,9 @@ static void sculpt_stroke_done(const bContext *C, struct PaintStroke *UNUSED(str
 		sculpt_undo_push_end();
 
 		BLI_pbvh_update(ss->pbvh, PBVH_UpdateOriginalBB, NULL);
+		
+		if (BLI_pbvh_type(ss->pbvh) == PBVH_BMESH)
+			BLI_pbvh_bmesh_after_stroke(ss->pbvh);
 
 		/* optimization: if there is locked key and active modifiers present in */
 		/* the stack, keyblock is updating at each step. otherwise we could update */
@@ -4054,7 +4409,7 @@ static int sculpt_brush_stroke_cancel(bContext *C, wmOperator *op)
 	Sculpt *sd = CTX_data_tool_settings(C)->sculpt;
 
 	if (ss->cache) {
-		paint_mesh_restore_co(sd, ss);
+		paint_mesh_restore_co(sd, ob);
 	}
 
 	paint_stroke_cancel(C, op);
@@ -4136,6 +4491,222 @@ static void SCULPT_OT_set_persistent_base(wmOperatorType *ot)
 	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 }
 
+/************************** Dynamic Topology **************************/
+
+static void sculpt_dynamic_topology_triangulate(BMesh *bm)
+{
+	BMO_op_callf(bm, BMO_FLAG_DEFAULTS, "triangulate faces=%af");
+}
+
+void sculpt_pbvh_clear(Object *ob)
+{
+	SculptSession *ss = ob->sculpt;
+	DerivedMesh *dm = ob->derivedFinal;
+
+	/* Clear out any existing DM and PBVH */
+	if (ss->pbvh)
+		BLI_pbvh_free(ss->pbvh);
+	ss->pbvh = NULL;
+	if (dm)
+		dm->getPBVH(NULL, dm);
+	BKE_object_free_display(ob);
+}
+
+void sculpt_update_after_dynamic_topology_toggle(bContext *C)
+{
+	Scene *scene = CTX_data_scene(C);
+	Object *ob = CTX_data_active_object(C);
+	Sculpt *sd = scene->toolsettings->sculpt;
+
+	/* Create the PBVH */
+	sculpt_update_mesh_elements(scene, sd, ob, FALSE, FALSE);
+	WM_event_add_notifier(C, NC_OBJECT | ND_DRAW, ob);
+}
+
+void sculpt_dynamic_topology_enable(bContext *C)
+{
+	Scene *scene = CTX_data_scene(C);
+	Object *ob = CTX_data_active_object(C);
+	SculptSession *ss = ob->sculpt;
+	Mesh *me = ob->data;
+
+	sculpt_pbvh_clear(ob);
+
+	ss->bm_smooth_shading = (scene->toolsettings->sculpt->flags &
+							 SCULPT_DYNTOPO_SMOOTH_SHADING);
+
+	/* Create triangles-only BMesh */
+	ss->bm = BM_mesh_create(&bm_mesh_allocsize_default);
+
+	BM_mesh_bm_from_me(ss->bm, me, TRUE, ob->shapenr);
+	sculpt_dynamic_topology_triangulate(ss->bm);
+	BM_data_layer_add(ss->bm, &ss->bm->vdata, CD_PAINT_MASK);
+	BM_mesh_normals_update(ss->bm, TRUE);
+
+	/* Enable dynamic topology */
+	me->flag |= ME_SCULPT_DYNAMIC_TOPOLOGY;
+	
+	/* Enable logging for undo/redo */
+	ss->bm_log = BM_log_create(ss->bm);
+
+	/* Refresh */
+	sculpt_update_after_dynamic_topology_toggle(C);
+}
+
+/* Free the sculpt BMesh and BMLog
+ *
+ * If 'unode' is given, the BMesh's data is copied out to the unode
+ * before the BMesh is deleted so that it can be restored from */
+void sculpt_dynamic_topology_disable(bContext *C,
+									 SculptUndoNode *unode)
+{
+	Object *ob = CTX_data_active_object(C);
+	SculptSession *ss = ob->sculpt;
+	Mesh *me = ob->data;
+
+	sculpt_pbvh_clear(ob);
+
+	if (unode) {
+		/* Free all existing custom data */
+		CustomData_free(&me->vdata, me->totvert);
+		CustomData_free(&me->edata, me->totedge);
+		CustomData_free(&me->fdata, me->totface);
+		CustomData_free(&me->ldata, me->totloop);
+		CustomData_free(&me->pdata, me->totpoly);
+
+		/* Copy over stored custom data */
+		me->totvert = unode->bm_enter_totvert;
+		me->totloop = unode->bm_enter_totloop;
+		me->totpoly = unode->bm_enter_totpoly;
+		me->totedge = unode->bm_enter_totedge;
+		me->totface = 0;
+		CustomData_copy(&unode->bm_enter_vdata, &me->vdata, CD_MASK_MESH,
+						CD_DUPLICATE, unode->bm_enter_totvert);
+		CustomData_copy(&unode->bm_enter_edata, &me->edata, CD_MASK_MESH,
+						CD_DUPLICATE, unode->bm_enter_totedge);
+		CustomData_copy(&unode->bm_enter_ldata, &me->ldata, CD_MASK_MESH,
+						CD_DUPLICATE, unode->bm_enter_totloop);
+		CustomData_copy(&unode->bm_enter_pdata, &me->pdata, CD_MASK_MESH,
+						CD_DUPLICATE, unode->bm_enter_totpoly);
+
+		mesh_update_customdata_pointers(me, FALSE);
+	} else {
+		sculptsession_bm_to_me(ob, TRUE);
+	}
+
+	BM_mesh_free(ss->bm);
+
+	/* Clear data */
+	me->flag &= ~ME_SCULPT_DYNAMIC_TOPOLOGY;
+	ss->bm = NULL;
+	BM_log_free(ss->bm_log);
+	ss->bm_log = NULL;
+
+	/* Refresh */
+	sculpt_update_after_dynamic_topology_toggle(C);
+}
+
+static int sculpt_dynamic_topology_toggle_exec(bContext *C, wmOperator *UNUSED(op))
+{
+	Object *ob = CTX_data_active_object(C);
+	SculptSession *ss = ob->sculpt;
+
+	if (ss->bm) {
+		sculpt_undo_push_begin("Dynamic topology disable");
+		sculpt_undo_push_node(ob, NULL, SCULPT_UNDO_DYNTOPO_END);
+		sculpt_dynamic_topology_disable(C, NULL);
+	}
+	else {
+		sculpt_undo_push_begin("Dynamic topology enable");
+		sculpt_dynamic_topology_enable(C);
+		sculpt_undo_push_node(ob, NULL, SCULPT_UNDO_DYNTOPO_BEGIN);
+	}
+	sculpt_undo_push_end();
+
+	return OPERATOR_FINISHED;
+}
+
+static int sculpt_dynamic_topology_toggle_invoke(bContext *C, wmOperator *op,
+												 wmEvent *UNUSED(event))
+{
+	Object *ob = CTX_data_active_object(C);
+	Mesh *me = ob->data;
+	SculptSession *ss = ob->sculpt;
+	const char *msg = "Dynamic-topology sculpting will not preserve"
+		              "vertex colors, UVs, or other customdata";
+
+	if (!ss->bm) {
+		int i;
+
+		for (i = 0; i < CD_NUMTYPES; i++) {
+			if (!ELEM7(i, CD_MVERT, CD_MEDGE, CD_MFACE,
+					   CD_MLOOP, CD_MPOLY, CD_PAINT_MASK,
+					   CD_ORIGINDEX) &&
+				(CustomData_has_layer(&me->vdata, i) ||
+				 CustomData_has_layer(&me->edata, i) ||
+				 CustomData_has_layer(&me->fdata, i))) {
+				/* The mesh has customdata that will be lost, let the
+				 * user confirm this is OK */
+				return WM_operator_confirm_message(C, op, msg);
+			}
+		}
+	}
+
+	return sculpt_dynamic_topology_toggle_exec(C, op);
+}
+
+static void SCULPT_OT_dynamic_topology_toggle(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Dynamic Topology Toggle";
+	ot->idname = "SCULPT_OT_dynamic_topology_toggle";
+	ot->description = "Dynamic topology alters the mesh topology while sculpting";
+	
+	/* api callbacks */
+	ot->invoke = sculpt_dynamic_topology_toggle_invoke;
+	ot->exec = sculpt_dynamic_topology_toggle_exec;
+	ot->poll = sculpt_mode_poll;
+	
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
+/************************* SCULPT_OT_optimize *************************/
+
+static int sculpt_optimize_exec(bContext *C, wmOperator *UNUSED(op))
+{
+	Object *ob = CTX_data_active_object(C);
+
+	sculpt_pbvh_clear(ob);
+	WM_event_add_notifier(C, NC_OBJECT | ND_DRAW, ob);
+
+	return OPERATOR_FINISHED;
+}
+
+static int sculpt_and_dynamic_topology_poll(bContext *C)
+{
+	Object *ob = CTX_data_active_object(C);
+
+	return sculpt_mode_poll(C) && ob->sculpt->bm;
+}
+
+/* The BVH gets less optimal more quickly with dynamic topology than
+ * regular sculpting. There is no doubt more clever stuff we can do to
+ * optimize it on the fly, but for now this gives the user a nicer way
+ * to recalculate it than toggling modes. */
+static void SCULPT_OT_optimize(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Optimize";
+	ot->idname = "SCULPT_OT_optimize";
+	ot->description = "Recalculate the sculpt BVH to improve performance";
+	
+	/* api callbacks */
+	ot->exec = sculpt_optimize_exec;
+	ot->poll = sculpt_and_dynamic_topology_poll;
+	
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
 /**** Toggle operator for turning sculpt mode on or off ****/
 
 static void sculpt_init_session(Scene *scene, Object *ob)
@@ -4221,6 +4792,7 @@ static int sculpt_toggle_mode(bContext *C, wmOperator *UNUSED(op))
 	Scene *scene = CTX_data_scene(C);
 	ToolSettings *ts = CTX_data_tool_settings(C);
 	Object *ob = CTX_data_active_object(C);
+	Mesh *me = ob->data;
 	MultiresModifierData *mmd = sculpt_multires_active(scene, ob);
 	int flush_recalc = 0;
 
@@ -4233,9 +4805,16 @@ static int sculpt_toggle_mode(bContext *C, wmOperator *UNUSED(op))
 		if (mmd)
 			multires_force_update(ob);
 
-		if (flush_recalc)
+		if (flush_recalc || (ob->sculpt && ob->sculpt->bm))
 			DAG_id_tag_update(&ob->id, OB_RECALC_DATA);
 
+		if (me->flag & ME_SCULPT_DYNAMIC_TOPOLOGY) {
+			/* Dynamic topology must be disabled before exiting sculpt
+			 * mode to ensure the undo stack stays in a consistent
+			 * state */
+			sculpt_dynamic_topology_toggle_exec(C, NULL);
+		}
+
 		/* Leave sculptmode */
 		ob->mode &= ~OB_MODE_SCULPT;
 
@@ -4256,6 +4835,9 @@ static int sculpt_toggle_mode(bContext *C, wmOperator *UNUSED(op))
 			ts->sculpt->flags |= SCULPT_SYMM_X;
 		}
 
+		if (!ts->sculpt->detail_size)
+			ts->sculpt->detail_size = 30;
+
 		/* Create sculpt mode session data */
 		if (ob->sculpt)
 			free_sculptsession(ob);
@@ -4270,7 +4852,7 @@ static int sculpt_toggle_mode(bContext *C, wmOperator *UNUSED(op))
 		}
 
 		BKE_paint_init(&ts->sculpt->paint, PAINT_CURSOR_SCULPT);
-		
+
 		paint_cursor_start(C, sculpt_poll);
 	}
 
@@ -4298,4 +4880,6 @@ void ED_operatortypes_sculpt(void)
 	WM_operatortype_append(SCULPT_OT_brush_stroke);
 	WM_operatortype_append(SCULPT_OT_sculptmode_toggle);
 	WM_operatortype_append(SCULPT_OT_set_persistent_base);
+	WM_operatortype_append(SCULPT_OT_dynamic_topology_toggle);
+	WM_operatortype_append(SCULPT_OT_optimize);
 }
diff --git a/source/blender/editors/sculpt_paint/sculpt_intern.h b/source/blender/editors/sculpt_paint/sculpt_intern.h
index cfc908bf453..e56962a3964 100644
--- a/source/blender/editors/sculpt_paint/sculpt_intern.h
+++ b/source/blender/editors/sculpt_paint/sculpt_intern.h
@@ -49,6 +49,7 @@ struct Object;
 struct Scene;
 struct Sculpt;
 struct SculptStroke;
+struct SculptUndoNode;
 
 /* Interface */
 struct MultiresModifierData *sculpt_multires_active(struct Scene *scene, struct Object *ob);
@@ -67,12 +68,22 @@ void free_sculptsession_deformMats(struct SculptSession *ss);
 /* Stroke */
 int sculpt_stroke_get_location(bContext *C, float out[3], const float mouse[2]);
 
+/* Dynamic topology */
+void sculpt_pbvh_clear(Object *ob);
+void sculpt_update_after_dynamic_topology_toggle(bContext *C);
+void sculpt_dynamic_topology_enable(struct bContext *C);
+void sculpt_dynamic_topology_disable(struct bContext *C,
+									 struct SculptUndoNode *unode);
+
 /* Undo */
 
 typedef enum {
 	SCULPT_UNDO_COORDS,
 	SCULPT_UNDO_HIDDEN,
-	SCULPT_UNDO_MASK
+	SCULPT_UNDO_MASK,
+	SCULPT_UNDO_DYNTOPO_BEGIN,
+	SCULPT_UNDO_DYNTOPO_END,
+	SCULPT_UNDO_DYNTOPO_SYMMETRIZE,
 } SculptUndoType;
 
 typedef struct SculptUndoNode {
@@ -101,6 +112,18 @@ typedef struct SculptUndoNode {
 	int *grids;                 /* to restore into right location */
 	BLI_bitmap *grid_hidden;
 
+	/* bmesh */
+	struct BMLogEntry *bm_entry;
+	int applied;
+	CustomData bm_enter_vdata;
+	CustomData bm_enter_edata;
+	CustomData bm_enter_ldata;
+	CustomData bm_enter_pdata;
+	int bm_enter_totvert;
+	int bm_enter_totedge;
+	int bm_enter_totloop;
+	int bm_enter_totpoly;
+
 	/* shape keys */
 	char shapeName[sizeof(((KeyBlock *)0))->name];
 } SculptUndoNode;
diff --git a/source/blender/editors/sculpt_paint/sculpt_undo.c b/source/blender/editors/sculpt_paint/sculpt_undo.c
index 053e17cde07..08e61a6d05d 100644
--- a/source/blender/editors/sculpt_paint/sculpt_undo.c
+++ b/source/blender/editors/sculpt_paint/sculpt_undo.c
@@ -65,6 +65,7 @@
 #include "GPU_buffers.h"
 
 #include "ED_sculpt.h"
+#include "bmesh.h"
 #include "paint_intern.h"
 #include "sculpt_intern.h"
 
@@ -261,6 +262,111 @@ static int sculpt_undo_restore_mask(bContext *C, DerivedMesh *dm, SculptUndoNode
 	return 1;
 }
 
+static void sculpt_undo_bmesh_restore_generic(SculptUndoNode *unode,
+											  Object *ob,
+											  SculptSession *ss)
+{
+	if (unode->applied) {
+		BM_log_undo(ss->bm, ss->bm_log);
+		unode->applied = FALSE;
+	}
+	else {
+		BM_log_redo(ss->bm, ss->bm_log);
+		unode->applied = TRUE;
+	}
+
+	/* A bit lame, but for now just recreate the PBVH. The alternative
+	 * is to store changes to the PBVH in the undo stack. */
+	sculpt_pbvh_clear(ob);
+}
+
+/* Create empty sculpt BMesh and enable logging */
+static void sculpt_undo_bmesh_enable(Object *ob,
+									 SculptUndoNode *unode)
+{
+	SculptSession *ss = ob->sculpt;
+	Mesh *me = ob->data;
+
+	sculpt_pbvh_clear(ob);
+
+	/* Create empty BMesh and enable logging */
+	ss->bm = BM_mesh_create(&bm_mesh_allocsize_default);
+	BM_data_layer_add(ss->bm, &ss->bm->vdata, CD_PAINT_MASK);
+	me->flag |= ME_SCULPT_DYNAMIC_TOPOLOGY;
+
+	/* Restore the BMLog using saved entries */
+	ss->bm_log = BM_log_from_existing_entries_create(ss->bm,
+													 unode->bm_entry);
+}
+
+static void sculpt_undo_bmesh_restore_begin(bContext *C,
+											SculptUndoNode *unode,
+											Object *ob,
+											SculptSession *ss)
+{
+	if (unode->applied) {
+		sculpt_dynamic_topology_disable(C, unode);
+		unode->applied = FALSE;
+	}
+	else {
+		sculpt_undo_bmesh_enable(ob, unode);
+
+		/* Restore the mesh from the first log entry */
+		BM_log_redo(ss->bm, ss->bm_log);
+
+		unode->applied = TRUE;
+	}
+}
+
+static void sculpt_undo_bmesh_restore_end(bContext *C,
+										  SculptUndoNode *unode,
+										  Object *ob,
+										  SculptSession *ss)
+{
+	if (unode->applied) {
+		sculpt_undo_bmesh_enable(ob, unode);
+
+		/* Restore the mesh from the last log entry */
+		BM_log_undo(ss->bm, ss->bm_log);
+
+		unode->applied = FALSE;
+	}
+	else {
+		/* Disable dynamic topology sculpting */
+		sculpt_dynamic_topology_disable(C, NULL);
+		unode->applied = TRUE;
+	}
+}
+
+/* Handle all dynamic-topology updates
+ *
+ * Returns TRUE if this was a dynamic-topology undo step, otherwise
+ * returns FALSE to indicate the non-dyntopo code should run. */
+static int sculpt_undo_bmesh_restore(bContext *C,
+									 SculptUndoNode *unode,
+									 Object *ob,
+									 SculptSession *ss)
+{
+	switch (unode->type) {
+		case SCULPT_UNDO_DYNTOPO_BEGIN:
+			sculpt_undo_bmesh_restore_begin(C, unode, ob, ss);
+			return TRUE;
+
+		case SCULPT_UNDO_DYNTOPO_END:
+			sculpt_undo_bmesh_restore_end(C, unode, ob, ss);
+			return TRUE;
+
+		default:
+			if (ss->bm_log) {
+				sculpt_undo_bmesh_restore_generic(unode, ob, ss);
+				return TRUE;
+			}
+			break;
+	}
+
+	return FALSE;
+}
+
 static void sculpt_undo_restore(bContext *C, ListBase *lb)
 {
 	Scene *scene = CTX_data_scene(C);
@@ -289,6 +395,9 @@ static void sculpt_undo_restore(bContext *C, ListBase *lb)
 	/* call _after_ sculpt_update_mesh_elements() which may update 'ob->derivedFinal' */
 	dm = mesh_get_derived_final(scene, ob, 0);
 
+	if (lb->first && sculpt_undo_bmesh_restore(C, lb->first, ob, ss))
+		return;
+
 	for (unode = lb->first; unode; unode = unode->next) {
 		if (!(strcmp(unode->idname, ob->id.name) == 0))
 			continue;
@@ -306,9 +415,6 @@ static void sculpt_undo_restore(bContext *C, ListBase *lb)
 				continue;
 			}
 		}
-		else {
-			continue;
-		}
 
 		switch (unode->type) {
 			case SCULPT_UNDO_COORDS:
@@ -323,6 +429,12 @@ static void sculpt_undo_restore(bContext *C, ListBase *lb)
 				if (sculpt_undo_restore_mask(C, dm, unode))
 					update = TRUE;
 				break;
+
+			case SCULPT_UNDO_DYNTOPO_BEGIN:
+			case SCULPT_UNDO_DYNTOPO_END:
+			case SCULPT_UNDO_DYNTOPO_SYMMETRIZE:
+				BLI_assert(!"Dynamic topology should've already been handled");
+				break;
 		}
 	}
 
@@ -387,6 +499,17 @@ static void sculpt_undo_free(ListBase *lb)
 		}
 		if (unode->mask)
 			MEM_freeN(unode->mask);
+		if (unode->bm_entry) {
+			BM_log_entry_drop(unode->bm_entry);
+		}
+		if (unode->bm_enter_totvert)
+			CustomData_free(&unode->bm_enter_vdata, unode->bm_enter_totvert);
+		if (unode->bm_enter_totedge)
+			CustomData_free(&unode->bm_enter_edata, unode->bm_enter_totedge);
+		if (unode->bm_enter_totloop)
+			CustomData_free(&unode->bm_enter_ldata, unode->bm_enter_totloop);
+		if (unode->bm_enter_totpoly)
+			CustomData_free(&unode->bm_enter_pdata, unode->bm_enter_totpoly);
 	}
 }
 
@@ -437,11 +560,13 @@ static SculptUndoNode *sculpt_undo_alloc_node(Object *ob, PBVHNode *node,
 	unode->type = type;
 	unode->node = node;
 
-	BLI_pbvh_node_num_verts(ss->pbvh, node, &totvert, &allvert);
-	BLI_pbvh_node_get_grids(ss->pbvh, node, &grids, &totgrid,
-	                        &maxgrid, &gridsize, NULL, NULL);
+	if (node) {
+		BLI_pbvh_node_num_verts(ss->pbvh, node, &totvert, &allvert);
+		BLI_pbvh_node_get_grids(ss->pbvh, node, &grids, &totgrid,
+								&maxgrid, &gridsize, NULL, NULL);
 
-	unode->totvert = totvert;
+		unode->totvert = totvert;
+	}
 	
 	/* we will use this while sculpting, is mapalloc slow to access then? */
 
@@ -466,6 +591,11 @@ static SculptUndoNode *sculpt_undo_alloc_node(Object *ob, PBVHNode *node,
 			unode->mask = MEM_mapallocN(sizeof(float) * allvert, "SculptUndoNode.mask");
 			undo_paint_push_count_alloc(UNDO_PAINT_MESH, (sizeof(float) * sizeof(int)) * allvert);
 			break;
+		case SCULPT_UNDO_DYNTOPO_BEGIN:
+		case SCULPT_UNDO_DYNTOPO_END:
+		case SCULPT_UNDO_DYNTOPO_SYMMETRIZE:
+			BLI_assert(!"Dynamic topology should've already been handled");
+			break;
 	}
 	
 	BLI_addtail(lb, unode);
@@ -540,6 +670,80 @@ static void sculpt_undo_store_mask(Object *ob, SculptUndoNode *unode)
 	BLI_pbvh_vertex_iter_end;
 }
 
+static SculptUndoNode *sculpt_undo_bmesh_push(Object *ob,
+											  PBVHNode *node,
+											  SculptUndoType type)
+{
+	ListBase *lb = undo_paint_push_get_list(UNDO_PAINT_MESH);
+	SculptUndoNode *unode = lb->first;
+	SculptSession *ss = ob->sculpt;
+	PBVHVertexIter vd;
+
+	if (!lb->first) {
+		unode = MEM_callocN(sizeof(*unode), AT);
+
+		BLI_strncpy(unode->idname, ob->id.name, sizeof(unode->idname));
+		unode->type = type;
+		unode->applied = TRUE;
+
+		if (type == SCULPT_UNDO_DYNTOPO_END) {
+			unode->bm_entry = BM_log_entry_add(ss->bm_log);
+			BM_log_before_all_removed(ss->bm, ss->bm_log);
+		}
+		else if (type == SCULPT_UNDO_DYNTOPO_BEGIN) {
+			Mesh *me = ob->data;
+
+			/* Store a copy of the mesh's current vertices, loops, and
+			 * polys. A full copy like this is needed because entering
+			 * dynamic-topology immediately does topological edits
+			 * (converting polys to triangles) that the BMLog can't
+			 * fully restore from */
+			CustomData_copy(&me->vdata, &unode->bm_enter_vdata, CD_MASK_MESH,
+							CD_DUPLICATE, me->totvert);
+			CustomData_copy(&me->edata, &unode->bm_enter_edata, CD_MASK_MESH,
+							CD_DUPLICATE, me->totedge);
+			CustomData_copy(&me->ldata, &unode->bm_enter_ldata, CD_MASK_MESH,
+							CD_DUPLICATE, me->totloop);
+			CustomData_copy(&me->pdata, &unode->bm_enter_pdata, CD_MASK_MESH,
+							CD_DUPLICATE, me->totpoly);
+			unode->bm_enter_totvert = me->totvert;
+			unode->bm_enter_totedge = me->totedge;
+			unode->bm_enter_totloop = me->totloop;
+			unode->bm_enter_totpoly = me->totpoly;
+
+			unode->bm_entry = BM_log_entry_add(ss->bm_log);
+			BM_log_all_added(ss->bm, ss->bm_log);
+		}
+		else {
+			unode->bm_entry = BM_log_entry_add(ss->bm_log);
+		}
+
+		BLI_addtail(lb, unode);
+	}
+
+	if (node) {
+		switch (type) {
+			case SCULPT_UNDO_COORDS:
+			case SCULPT_UNDO_HIDDEN:
+			case SCULPT_UNDO_MASK:
+				/* Before any vertex values get modified, ensure their
+				 * original positions are logged */
+				BLI_pbvh_vertex_iter_begin(ss->pbvh, node, vd, PBVH_ITER_ALL) {
+					BM_log_vert_before_modified(ss->bm, ss->bm_log, vd.bm_vert);
+				}
+				BLI_pbvh_vertex_iter_end;
+				break;
+
+			case SCULPT_UNDO_DYNTOPO_BEGIN:
+			case SCULPT_UNDO_DYNTOPO_END:
+			case SCULPT_UNDO_DYNTOPO_SYMMETRIZE:
+				break;
+		}
+	}
+
+	return unode;
+}
+
 SculptUndoNode *sculpt_undo_push_node(Object *ob, PBVHNode *node,
                                       SculptUndoType type)
 {
@@ -549,7 +753,18 @@ SculptUndoNode *sculpt_undo_push_node(Object *ob, PBVHNode *node,
 	/* list is manipulated by multiple threads, so we lock */
 	BLI_lock_thread(LOCK_CUSTOM1);
 
-	if ((unode = sculpt_undo_get_node(node))) {
+	if (ss->bm ||
+		ELEM(type,
+			 SCULPT_UNDO_DYNTOPO_BEGIN,
+			 SCULPT_UNDO_DYNTOPO_END))
+	{
+		/* Dynamic topology stores only one undo node per stroke,
+		 * regardless of the number of PBVH nodes modified */
+		unode = sculpt_undo_bmesh_push(ob, node, type);
+		BLI_unlock_thread(LOCK_CUSTOM1);
+		return unode;
+	}
+	else if ((unode = sculpt_undo_get_node(node))) {
 		BLI_unlock_thread(LOCK_CUSTOM1);
 		return unode;
 	}
@@ -583,6 +798,11 @@ SculptUndoNode *sculpt_undo_push_node(Object *ob, PBVHNode *node,
 		case SCULPT_UNDO_MASK:
 			sculpt_undo_store_mask(ob, unode);
 			break;
+		case SCULPT_UNDO_DYNTOPO_BEGIN:
+		case SCULPT_UNDO_DYNTOPO_END:
+		case SCULPT_UNDO_DYNTOPO_SYMMETRIZE:
+			BLI_assert(!"Dynamic topology should've already been handled");
+			break;
 	}
 
 	/* store active shape key */