Sculpt/2.5:

* Added toolbar UI for setting "anchored" mode
* Added a "persistent" mode for the layer brush; basically you can keep sculpting on the same layer between strokes when this is on. There's a button to reset the base so you can add another layer on top of that, and so on.
This feature was suggested by Blenderer on BA, thanks!

Note, I think these options could use better names in the UI, but I couldn't really think of anything very descriptive, suggestions welcome

release/ui/space_view3d_toolbar.py

@@ -369,8 +369,15 @@ class VIEW3D_PT_tools_brush(PaintPanel):
 			
 				col = layout.column()
 				col.itemR(brush, "airbrush")
+				if brush.sculpt_tool != 'LAYER':
+					col.itemR(brush, "anchored")
+
 				if brush.sculpt_tool in ('DRAW', 'PINCH', 'INFLATE', 'LAYER', 'CLAY'):
 					col.itemR(brush, "flip_direction")
+
+				if brush.sculpt_tool == 'LAYER':
+					col.itemR(brush, "persistent")
+					col.itemO("sculpt.set_persistent_base")
 				
 		# Texture Paint Mode #
 		

source/blender/blenkernel/BKE_sculpt.h

@@ -59,6 +59,10 @@ typedef struct SculptSession {
 	/* Used to cache the render of the active texture */
 	unsigned int texcache_side, *texcache, texcache_actual;
 
+	/* Layer brush persistence between strokes */
+ 	float (*mesh_co_orig)[3]; /* Copy of the mesh vertices' locations */
+	float *layer_disps; /* Displacements for each vertex */
+
 	void *cursor; /* wm handle */
 
 	struct SculptStroke *stroke;

source/blender/blenkernel/intern/scene.c

@@ -689,6 +689,13 @@ void sculptsession_free(Sculpt *sculpt)
 
 		if(ss->texcache)
 			MEM_freeN(ss->texcache);
+
+		if(ss->layer_disps)
+			MEM_freeN(ss->layer_disps);
+
+		if(ss->mesh_co_orig)
+			MEM_freeN(ss->mesh_co_orig);
+
 		MEM_freeN(ss);
 		sculpt->session= NULL;
 	}

source/blender/editors/sculpt_paint/sculpt.c

@@ -145,8 +145,6 @@ typedef struct StrokeCache {
 	ViewContext vc;
 	bglMats *mats;
 
-	float *layer_disps; /* Displacements for each vertex */
- 	float (*mesh_store)[3]; /* Copy of the mesh vertices' locations */
 	short (*orig_norms)[3]; /* Copy of the mesh vertices' normals */
 	float (*face_norms)[3]; /* Copy of the mesh faces' normals */
 	float rotation; /* Texture rotation (radians) for anchored and rake modes */
@@ -459,7 +457,7 @@ static void do_layer_brush(Sculpt *sd, SculptSession *ss, const ListBase *active
 	calc_area_normal(sd, area_normal, active_verts);
 
 	while(node){
-		float *disp= &ss->cache->layer_disps[node->Index];
+		float *disp= &ss->layer_disps[node->Index];
 		float *co= ss->mvert[node->Index].co;
 		float val[3];
 		
@@ -469,9 +467,9 @@ static void do_layer_brush(Sculpt *sd, SculptSession *ss, const ListBase *active
 		if((lim < 0 && *disp < lim) || (lim > 0 && *disp > lim))
 			*disp = lim;
 		
-		val[0] = ss->cache->mesh_store[node->Index][0]+area_normal[0] * *disp*ss->cache->scale[0];
-		val[1] = ss->cache->mesh_store[node->Index][1]+area_normal[1] * *disp*ss->cache->scale[1];
-		val[2] = ss->cache->mesh_store[node->Index][2]+area_normal[2] * *disp*ss->cache->scale[2];
+		val[0] = ss->mesh_co_orig[node->Index][0]+area_normal[0] * *disp*ss->cache->scale[0];
+		val[1] = ss->mesh_co_orig[node->Index][1]+area_normal[1] * *disp*ss->cache->scale[1];
+		val[2] = ss->mesh_co_orig[node->Index][2]+area_normal[2] * *disp*ss->cache->scale[2];
 
 		sculpt_clip(sd, co, val);
 
@@ -1170,10 +1168,6 @@ static float unproject_brush_radius(SculptSession *ss, float offset)
 
 static void sculpt_cache_free(StrokeCache *cache)
 {
-	if(cache->layer_disps)
-		MEM_freeN(cache->layer_disps);
-	if(cache->mesh_store)
-		MEM_freeN(cache->mesh_store);
 	if(cache->orig_norms)
 		MEM_freeN(cache->orig_norms);
 	if(cache->face_norms)
@@ -1209,14 +1203,24 @@ static void sculpt_update_cache_invariants(Sculpt *sd, bContext *C, wmOperator *
 
 	sculpt_update_mesh_elements(C);
 
-	if(sd->brush->sculpt_tool == SCULPT_TOOL_LAYER)
-		cache->layer_disps = MEM_callocN(sizeof(float) * sd->session->totvert, "layer brush displacements");
+	/* Initialize layer brush displacements */
+	if(sd->brush->sculpt_tool == SCULPT_TOOL_LAYER &&
+	   (!sd->session->layer_disps || !(sd->brush->flag & BRUSH_PERSISTENT))) {
+		if(sd->session->layer_disps)
+			MEM_freeN(sd->session->layer_disps);
+		sd->session->layer_disps = MEM_callocN(sizeof(float) * sd->session->totvert, "layer brush displacements");
+	}
 
 	/* Make copies of the mesh vertex locations and normals for some tools */
 	if(sd->brush->sculpt_tool == SCULPT_TOOL_LAYER || (sd->brush->flag & BRUSH_ANCHORED)) {
-		cache->mesh_store= MEM_mallocN(sizeof(float) * 3 * sd->session->totvert, "sculpt mesh vertices copy");
-		for(i = 0; i < sd->session->totvert; ++i)
-			VecCopyf(cache->mesh_store[i], sd->session->mvert[i].co);
+		if(sd->brush->sculpt_tool != SCULPT_TOOL_LAYER ||
+		   !sd->session->mesh_co_orig || !(sd->brush->flag & BRUSH_PERSISTENT)) {
+			if(!sd->session->mesh_co_orig)
+				sd->session->mesh_co_orig= MEM_mallocN(sizeof(float) * 3 * sd->session->totvert,
+								       "sculpt mesh vertices copy");
+			for(i = 0; i < sd->session->totvert; ++i)
+				VecCopyf(sd->session->mesh_co_orig[i], sd->session->mvert[i].co);
+		}
 
 		if(sd->brush->flag & BRUSH_ANCHORED) {
 			cache->orig_norms= MEM_mallocN(sizeof(short) * 3 * sd->session->totvert, "Sculpt orig norm");
@@ -1360,9 +1364,9 @@ static void sculpt_restore_mesh(Sculpt *sd)
 	int i;
 	
 	/* Restore the mesh before continuing with anchored stroke */
-	if((sd->brush->flag & BRUSH_ANCHORED) && cache->mesh_store) {
+	if((sd->brush->flag & BRUSH_ANCHORED) && ss->mesh_co_orig) {
 		for(i = 0; i < ss->totvert; ++i) {
-			VecCopyf(ss->mvert[i].co, cache->mesh_store[i]);
+			VecCopyf(ss->mvert[i].co, ss->mesh_co_orig[i]);
 			ss->mvert[i].no[0] = cache->orig_norms[i][0];
 			ss->mvert[i].no[1] = cache->orig_norms[i][1];
 			ss->mvert[i].no[2] = cache->orig_norms[i][2];
@@ -1375,7 +1379,7 @@ static void sculpt_restore_mesh(Sculpt *sd)
 		}
 
 		if(sd->brush->sculpt_tool == SCULPT_TOOL_LAYER)
-			memset(cache->layer_disps, 0, sizeof(float) * ss->totvert);
+			memset(ss->layer_disps, 0, sizeof(float) * ss->totvert);
 	}
 }
 
@@ -1610,6 +1614,38 @@ static void SCULPT_OT_brush_stroke(wmOperatorType *ot)
 	RNA_def_float(ot->srna, "depth", 0.0f, 0.0f, FLT_MAX, "depth", "", 0.0f, FLT_MAX);
 }
 
+/**** Reset the copy of the mesh that is being sculpted on (currently just for the layer brush) ****/
+
+static int sculpt_set_persistent_base(bContext *C, wmOperator *op)
+{
+	SculptSession *ss = CTX_data_tool_settings(C)->sculpt->session;
+
+	if(ss) {
+		if(ss->layer_disps)
+			MEM_freeN(ss->layer_disps);
+		ss->layer_disps = NULL;
+
+		if(ss->mesh_co_orig)
+			MEM_freeN(ss->mesh_co_orig);
+		ss->mesh_co_orig = NULL;
+	}
+
+	return OPERATOR_FINISHED;
+}
+
+static void SCULPT_OT_set_persistent_base(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name= "Set Persistent Base";
+	ot->idname= "SCULPT_OT_set_persistent_base";
+	
+	/* api callbacks */
+	ot->exec= sculpt_set_persistent_base;
+	ot->poll= sculpt_mode_poll;
+	
+	ot->flag= OPTYPE_REGISTER;
+}
+
 /**** Toggle operator for turning sculpt mode on or off ****/
 
 static int sculpt_toggle_mode(bContext *C, wmOperator *op)
@@ -1670,4 +1706,5 @@ void ED_operatortypes_sculpt()
 	WM_operatortype_append(SCULPT_OT_brush_stroke);
 	WM_operatortype_append(SCULPT_OT_sculptmode_toggle);
 	WM_operatortype_append(SCULPT_OT_brush_curve_preset);
+	WM_operatortype_append(SCULPT_OT_set_persistent_base);
 }

source/blender/makesdna/DNA_brush_types.h

@@ -85,6 +85,7 @@ typedef struct Brush {
 #define BRUSH_DIR_IN		512
 #define BRUSH_SPACE		1024
 #define BRUSH_SMOOTH_STROKE	2048
+#define BRUSH_PERSISTENT	4096
 
 /* Brush.blend */
 #define BRUSH_BLEND_MIX 		0

source/blender/makesrna/intern/rna_brush.c

@@ -220,6 +220,10 @@ void rna_def_brush(BlenderRNA *brna)
 	prop= RNA_def_property(srna, "smooth_stroke", PROP_BOOLEAN, PROP_NONE);
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", BRUSH_SMOOTH_STROKE);
 	RNA_def_property_ui_text(prop, "Smooth Stroke", "Brush lags behind mouse and follows a smoother path.");
+
+	prop= RNA_def_property(srna, "persistent", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", BRUSH_PERSISTENT);
+	RNA_def_property_ui_text(prop, "Persistent", "Sculpts on a persistent layer of the mesh.");
 	
 	/* not exposed in the interface yet
 	prop= RNA_def_property(srna, "fixed_tex", PROP_BOOLEAN, PROP_NONE);