diff --git a/src/admesh/shared.cpp b/src/admesh/shared.cpp
index e9f075498..7da2841b0 100644
--- a/src/admesh/shared.cpp
+++ b/src/admesh/shared.cpp
@@ -29,19 +29,13 @@
 
 #include "stl.h"
 
-void stl_invalidate_shared_vertices(stl_file *stl)
-{
-  	stl->v_indices.clear();
-  	stl->v_shared.clear();
-}
-
-void stl_generate_shared_vertices(stl_file *stl)
+void stl_generate_shared_vertices(stl_file *stl, indexed_triangle_set &its)
 {
 	// 3 indices to vertex per face
-	stl->v_indices.assign(stl->stats.number_of_facets, v_indices_struct());
+	its.indices.assign(stl->stats.number_of_facets, v_indices_struct());
 	// Shared vertices (3D coordinates)
-	stl->v_shared.clear();
-	stl->v_shared.reserve(stl->stats.number_of_facets / 2);
+	its.vertices.clear();
+	its.vertices.reserve(stl->stats.number_of_facets / 2);
 
 	// A degenerate mesh may contain loops: Traversing a fan will end up in an endless loop
 	// while never reaching the starting face. To avoid these endless loops, traversed faces at each fan traversal
@@ -51,11 +45,11 @@ void stl_generate_shared_vertices(stl_file *stl)
 
 	for (uint32_t facet_idx = 0; facet_idx < stl->stats.number_of_facets; ++ facet_idx) {
 		for (int j = 0; j < 3; ++ j) {
-			if (stl->v_indices[facet_idx].vertex[j] != -1)
+			if (its.indices[facet_idx].vertex[j] != -1)
 				// Shared vertex was already assigned.
 				continue;
 			// Create a new shared vertex.
-			stl->v_shared.emplace_back(stl->facet_start[facet_idx].vertex[j]);
+			its.vertices.emplace_back(stl->facet_start[facet_idx].vertex[j]);
 			// Traverse the fan around the j-th vertex of the i-th face, assign the newly created shared vertex index to all the neighboring triangles in the triangle fan.
 			int  facet_in_fan_idx 	= facet_idx;
 			bool edge_direction 	= false;
@@ -89,7 +83,7 @@ void stl_generate_shared_vertices(stl_file *stl)
 			    		next_edge    = pivot_vertex;
 			  		}
 				}
-				stl->v_indices[facet_in_fan_idx].vertex[pivot_vertex] = stl->v_shared.size() - 1;
+				its.indices[facet_in_fan_idx].vertex[pivot_vertex] = its.vertices.size() - 1;
 				fan_traversal_facet_visited[facet_in_fan_idx] = fan_traversal_stamp;
 
 				// next_edge is an index of the starting vertex of the edge, not an index of the opposite vertex to the edge!
@@ -130,7 +124,7 @@ void stl_generate_shared_vertices(stl_file *stl)
 	}
 }
 
-bool stl_write_off(stl_file *stl, const char *file)
+bool its_write_off(const indexed_triangle_set &its, const char *file)
 {
 	/* Open the file */
 	FILE *fp = boost::nowide::fopen(file, "w");
@@ -143,16 +137,16 @@ bool stl_write_off(stl_file *stl, const char *file)
 	}
 
 	fprintf(fp, "OFF\n");
-	fprintf(fp, "%d %d 0\n", stl->v_shared.size(), stl->stats.number_of_facets);
-	for (int i = 0; i < stl->v_shared.size(); ++ i)
-		fprintf(fp, "\t%f %f %f\n", stl->v_shared[i](0), stl->v_shared[i](1), stl->v_shared[i](2));
-	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i)
-		fprintf(fp, "\t3 %d %d %d\n", stl->v_indices[i].vertex[0], stl->v_indices[i].vertex[1], stl->v_indices[i].vertex[2]);
+	fprintf(fp, "%d %d 0\n", (int)its.vertices.size(), (int)its.indices.size());
+	for (int i = 0; i < its.vertices.size(); ++ i)
+		fprintf(fp, "\t%f %f %f\n", its.vertices[i](0), its.vertices[i](1), its.vertices[i](2));
+	for (uint32_t i = 0; i < its.indices.size(); ++ i)
+		fprintf(fp, "\t3 %d %d %d\n", its.indices[i].vertex[0], its.indices[i].vertex[1], its.indices[i].vertex[2]);
 	fclose(fp);
 	return true;
 }
 
-bool stl_write_vrml(stl_file *stl, const char *file)
+bool its_write_vrml(const indexed_triangle_set &its, const char *file)
 {
 	/* Open the file */
   	FILE *fp = boost::nowide::fopen(file, "w");
@@ -180,16 +174,16 @@ bool stl_write_vrml(stl_file *stl, const char *file)
 	fprintf(fp, "\t\t\tpoint [\n");
 
 	int i = 0;
-	for (; i + 1 < stl->v_shared.size(); ++ i)
-		fprintf(fp, "\t\t\t\t%f %f %f,\n", stl->v_shared[i](0), stl->v_shared[i](1), stl->v_shared[i](2));
-	fprintf(fp, "\t\t\t\t%f %f %f]\n", stl->v_shared[i](0), stl->v_shared[i](1), stl->v_shared[i](2));
+	for (; i + 1 < its.vertices.size(); ++ i)
+		fprintf(fp, "\t\t\t\t%f %f %f,\n", its.vertices[i](0), its.vertices[i](1), its.vertices[i](2));
+	fprintf(fp, "\t\t\t\t%f %f %f]\n", its.vertices[i](0), its.vertices[i](1), its.vertices[i](2));
 	fprintf(fp, "\t\t}\n");
 	fprintf(fp, "\t\tDEF STLTriangles IndexedFaceSet {\n");
 	fprintf(fp, "\t\t\tcoordIndex [\n");
 
-	for (int i = 0; i + 1 < (int)stl->stats.number_of_facets; ++ i)
-		fprintf(fp, "\t\t\t\t%d, %d, %d, -1,\n", stl->v_indices[i].vertex[0], stl->v_indices[i].vertex[1], stl->v_indices[i].vertex[2]);
-	fprintf(fp, "\t\t\t\t%d, %d, %d, -1]\n", stl->v_indices[i].vertex[0], stl->v_indices[i].vertex[1], stl->v_indices[i].vertex[2]);
+	for (size_t i = 0; i + 1 < its.indices.size(); ++ i)
+		fprintf(fp, "\t\t\t\t%d, %d, %d, -1,\n", its.indices[i].vertex[0], its.indices[i].vertex[1], its.indices[i].vertex[2]);
+	fprintf(fp, "\t\t\t\t%d, %d, %d, -1]\n", its.indices[i].vertex[0], its.indices[i].vertex[1], its.indices[i].vertex[2]);
 	fprintf(fp, "\t\t}\n");
 	fprintf(fp, "\t}\n");
 	fprintf(fp, "}\n");
@@ -197,7 +191,7 @@ bool stl_write_vrml(stl_file *stl, const char *file)
 	return true;
 }
 
-bool stl_write_obj(stl_file *stl, const char *file)
+bool its_write_obj(const indexed_triangle_set &its, const char *file)
 {
 
   	FILE *fp = boost::nowide::fopen(file, "w");
@@ -209,10 +203,65 @@ bool stl_write_obj(stl_file *stl, const char *file)
     	return false;
   	}
 
-	for (size_t i = 0; i < stl->v_shared.size(); ++ i)
-    	fprintf(fp, "v %f %f %f\n", stl->v_shared[i](0), stl->v_shared[i](1), stl->v_shared[i](2));
-  	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i)
-    	fprintf(fp, "f %d %d %d\n", stl->v_indices[i].vertex[0]+1, stl->v_indices[i].vertex[1]+1, stl->v_indices[i].vertex[2]+1);
+	for (size_t i = 0; i < its.vertices.size(); ++ i)
+    	fprintf(fp, "v %f %f %f\n", its.vertices[i](0), its.vertices[i](1), its.vertices[i](2));
+  	for (size_t i = 0; i < its.indices.size(); ++ i)
+    	fprintf(fp, "f %d %d %d\n", its.indices[i].vertex[0]+1, its.indices[i].vertex[1]+1, its.indices[i].vertex[2]+1);
   	fclose(fp);
   	return true;
 }
+
+
+// Check validity of the mesh, assert on error.
+bool stl_validate(const stl_file *stl, const indexed_triangle_set &its)
+{
+	assert(! stl->facet_start.empty());
+	assert(stl->facet_start.size() == stl->stats.number_of_facets);
+	assert(stl->neighbors_start.size() == stl->stats.number_of_facets);
+	assert(stl->facet_start.size() == stl->neighbors_start.size());
+	assert(! stl->neighbors_start.empty());
+	assert((its.indices.empty()) == (its.vertices.empty()));
+	assert(stl->stats.number_of_facets > 0);
+	assert(its.vertices.empty() || its.indices.size() == stl->stats.number_of_facets);
+
+#ifdef _DEBUG
+    // Verify validity of neighborship data.
+    for (int facet_idx = 0; facet_idx < (int)stl->stats.number_of_facets; ++ facet_idx) {
+        const stl_neighbors &nbr 		= stl->neighbors_start[facet_idx];
+        const int 			*vertices 	= (its.indices.empty()) ? nullptr : its.indices[facet_idx].vertex;
+        for (int nbr_idx = 0; nbr_idx < 3; ++ nbr_idx) {
+            int nbr_face = stl->neighbors_start[facet_idx].neighbor[nbr_idx];
+            assert(nbr_face < (int)stl->stats.number_of_facets);
+            if (nbr_face != -1) {
+            	int nbr_vnot = nbr.which_vertex_not[nbr_idx];
+				assert(nbr_vnot >= 0 && nbr_vnot < 6);
+				// Neighbor of the neighbor is the original face.
+				assert(stl->neighbors_start[nbr_face].neighbor[(nbr_vnot + 1) % 3] == facet_idx);
+				int vnot_back = stl->neighbors_start[nbr_face].which_vertex_not[(nbr_vnot + 1) % 3];
+				assert(vnot_back >= 0 && vnot_back < 6);
+				assert((nbr_vnot < 3) == (vnot_back < 3));
+				assert(vnot_back % 3 == (nbr_idx + 2) % 3);
+				if (vertices != nullptr) {
+					// Has shared vertices.
+	            	if (nbr_vnot < 3) {
+	            		// Faces facet_idx and nbr_face share two vertices accross the common edge. Faces are correctly oriented.
+						assert((its.indices[nbr_face].vertex[(nbr_vnot + 1) % 3] == vertices[(nbr_idx + 1) % 3] && its.indices[nbr_face].vertex[(nbr_vnot + 2) % 3] == vertices[nbr_idx]));
+					} else {
+	            		// Faces facet_idx and nbr_face share two vertices accross the common edge. Faces are incorrectly oriented, one of them is flipped.
+						assert((its.indices[nbr_face].vertex[(nbr_vnot + 2) % 3] == vertices[(nbr_idx + 1) % 3] && its.indices[nbr_face].vertex[(nbr_vnot + 1) % 3] == vertices[nbr_idx]));
+					}
+				}
+            }
+        }
+    }
+#endif /* _DEBUG */
+
+	return true;
+}
+
+// Check validity of the mesh, assert on error.
+bool stl_validate(const stl_file *stl)
+{
+	indexed_triangle_set its;
+	return stl_validate(stl, its);
+}
diff --git a/src/admesh/stl.h b/src/admesh/stl.h
index 4aee6048f..bb5d25296 100644
--- a/src/admesh/stl.h
+++ b/src/admesh/stl.h
@@ -130,21 +130,22 @@ struct stl_stats {
 struct stl_file {
 	std::vector<stl_facet>     		facet_start;
 	std::vector<stl_neighbors> 		neighbors_start;
-	// Indexed face set
-	std::vector<v_indices_struct> 	v_indices;
-	std::vector<stl_vertex>       	v_shared;
 	// Statistics
 	stl_stats     					stats;
 };
 
+struct indexed_triangle_set
+{
+	void clear() { indices.clear(); vertices.clear(); }
+	std::vector<v_indices_struct> 	indices;
+	std::vector<stl_vertex>       	vertices;
+};
+
 extern bool stl_open(stl_file *stl, const char *file);
 extern void stl_stats_out(stl_file *stl, FILE *file, char *input_file);
 extern bool stl_print_neighbors(stl_file *stl, char *file);
-extern void stl_put_little_int(FILE *fp, int value_in);
-extern void stl_put_little_float(FILE *fp, float value_in);
 extern bool stl_write_ascii(stl_file *stl, const char *file, const char *label);
 extern bool stl_write_binary(stl_file *stl, const char *file, const char *label);
-extern void stl_write_binary_block(stl_file *stl, FILE *fp);
 extern void stl_check_facets_exact(stl_file *stl);
 extern void stl_check_facets_nearby(stl_file *stl, float tolerance);
 extern void stl_remove_unconnected_facets(stl_file *stl);
@@ -219,12 +220,12 @@ inline void stl_transform(stl_file *stl, const Eigen::Matrix<T, 3, 3, Eigen::Don
 	stl_get_size(stl);
 }
 
-extern void stl_invalidate_shared_vertices(stl_file *stl);
-extern void stl_generate_shared_vertices(stl_file *stl);
-extern bool stl_write_obj(stl_file *stl, const char *file);
-extern bool stl_write_off(stl_file *stl, const char *file);
+extern void stl_generate_shared_vertices(stl_file *stl, indexed_triangle_set &its);
+extern bool its_write_obj(const indexed_triangle_set &its, const char *file);
+extern bool its_write_off(const indexed_triangle_set &its, const char *file);
+extern bool its_write_vrml(const indexed_triangle_set &its, const char *file);
+
 extern bool stl_write_dxf(stl_file *stl, const char *file, char *label);
-extern bool stl_write_vrml(stl_file *stl, const char *file);
 inline void stl_calculate_normal(stl_normal &normal, stl_facet *facet) {
   normal = (facet->vertex[1] - facet->vertex[0]).cross(facet->vertex[2] - facet->vertex[0]);
 }
@@ -251,6 +252,7 @@ extern void stl_reallocate(stl_file *stl);
 extern void stl_add_facet(stl_file *stl, const stl_facet *new_facet);
 
 // Validate the mesh, assert on error.
-extern bool stl_validate(stl_file *stl);
+extern bool stl_validate(const stl_file *stl);
+extern bool stl_validate(const stl_file *stl, const indexed_triangle_set &its);
 
 #endif
diff --git a/src/admesh/stlinit.cpp b/src/admesh/stlinit.cpp
index 088842d51..44477511f 100644
--- a/src/admesh/stlinit.cpp
+++ b/src/admesh/stlinit.cpp
@@ -253,8 +253,6 @@ void stl_reset(stl_file *stl)
 {
 	stl->facet_start.clear();
 	stl->neighbors_start.clear();
-	stl->v_indices.clear();
-	stl->v_shared.clear();
   	memset(&stl->stats, 0, sizeof(stl_stats));
   	stl->stats.volume = -1.0;
 }
diff --git a/src/admesh/util.cpp b/src/admesh/util.cpp
index 685b641b4..f4e4dbf0a 100644
--- a/src/admesh/util.cpp
+++ b/src/admesh/util.cpp
@@ -73,7 +73,6 @@ void stl_translate(stl_file *stl, float x, float y, float z)
       stl->facet_start[i].vertex[j] += shift;
   stl->stats.min = new_min;
   stl->stats.max += shift;
-  stl_invalidate_shared_vertices(stl);
 }
 
 /* Translates the stl by x,y,z, relatively from wherever it is currently */
@@ -85,7 +84,6 @@ void stl_translate_relative(stl_file *stl, float x, float y, float z)
       stl->facet_start[i].vertex[j] += shift;
   stl->stats.min += shift;
   stl->stats.max += shift;
-  stl_invalidate_shared_vertices(stl);
 }
 
 void stl_scale_versor(stl_file *stl, const stl_vertex &versor)
@@ -103,7 +101,6 @@ void stl_scale_versor(stl_file *stl, const stl_vertex &versor)
   for (int i = 0; i < stl->stats.number_of_facets; ++ i)
     for (int j = 0; j < 3; ++ j)
       stl->facet_start[i].vertex[j].array() *= s;
-  stl_invalidate_shared_vertices(stl);
 }
 
 static void calculate_normals(stl_file *stl) 
@@ -414,50 +411,3 @@ All facets connected.  No further nearby check necessary.\n");
     stl_verify_neighbors(stl);
   }
 }
-
-// Check validity of the mesh, assert on error.
-bool stl_validate(stl_file *stl)
-{
-	assert(! stl->facet_start.empty());
-	assert(stl->facet_start.size() == stl->stats.number_of_facets);
-	assert(stl->neighbors_start.size() == stl->stats.number_of_facets);
-	assert(stl->facet_start.size() == stl->neighbors_start.size());
-	assert(! stl->neighbors_start.empty());
-	assert((stl->v_indices.empty()) == (stl->v_shared.empty()));
-	assert(stl->stats.number_of_facets > 0);
-	assert(stl->v_shared.empty() || stl->v_indices.size() == stl->stats.number_of_facets);
-
-#ifdef _DEBUG
-    // Verify validity of neighborship data.
-    for (int facet_idx = 0; facet_idx < (int)stl->stats.number_of_facets; ++ facet_idx) {
-        const stl_neighbors &nbr 		= stl->neighbors_start[facet_idx];
-        const int 			*vertices 	= (stl->v_indices.empty()) ? nullptr : stl->v_indices[facet_idx].vertex;
-        for (int nbr_idx = 0; nbr_idx < 3; ++ nbr_idx) {
-            int nbr_face = stl->neighbors_start[facet_idx].neighbor[nbr_idx];
-            assert(nbr_face < (int)stl->stats.number_of_facets);
-            if (nbr_face != -1) {
-            	int nbr_vnot = nbr.which_vertex_not[nbr_idx];
-				assert(nbr_vnot >= 0 && nbr_vnot < 6);
-				// Neighbor of the neighbor is the original face.
-				assert(stl->neighbors_start[nbr_face].neighbor[(nbr_vnot + 1) % 3] == facet_idx);
-				int vnot_back = stl->neighbors_start[nbr_face].which_vertex_not[(nbr_vnot + 1) % 3];
-				assert(vnot_back >= 0 && vnot_back < 6);
-				assert((nbr_vnot < 3) == (vnot_back < 3));
-				assert(vnot_back % 3 == (nbr_idx + 2) % 3);
-				if (vertices != nullptr) {
-					// Has shared vertices.
-	            	if (nbr_vnot < 3) {
-	            		// Faces facet_idx and nbr_face share two vertices accross the common edge. Faces are correctly oriented.
-						assert((stl->v_indices[nbr_face].vertex[(nbr_vnot + 1) % 3] == vertices[(nbr_idx + 1) % 3] && stl->v_indices[nbr_face].vertex[(nbr_vnot + 2) % 3] == vertices[nbr_idx]));
-					} else {
-	            		// Faces facet_idx and nbr_face share two vertices accross the common edge. Faces are incorrectly oriented, one of them is flipped.
-						assert((stl->v_indices[nbr_face].vertex[(nbr_vnot + 2) % 3] == vertices[(nbr_idx + 1) % 3] && stl->v_indices[nbr_face].vertex[(nbr_vnot + 1) % 3] == vertices[nbr_idx]));
-					}
-				}
-            }
-        }
-    }
-#endif /* _DEBUG */
-
-	return true;
-}
diff --git a/src/libslic3r/Format/3mf.cpp b/src/libslic3r/Format/3mf.cpp
index d67106656..8298fe222 100644
--- a/src/libslic3r/Format/3mf.cpp
+++ b/src/libslic3r/Format/3mf.cpp
@@ -1881,27 +1881,23 @@ namespace Slic3r {
 
             volumes_offsets.insert(VolumeToOffsetsMap::value_type(volume, Offsets(vertices_count))).first;
 
-            if (!volume->mesh.repaired)
-                volume->mesh.repair();
+			volume->mesh.require_shared_vertices();
 
-            stl_file& stl = volume->mesh.stl;
-            if (stl.v_shared.empty())
-                stl_generate_shared_vertices(&stl);
-
-            if (stl.v_shared.empty())
+            const indexed_triangle_set &its = volume->mesh.its;
+            if (its.vertices.empty())
             {
                 add_error("Found invalid mesh");
                 return false;
             }
 
-            vertices_count += stl.v_shared.size();
+            vertices_count += its.vertices.size();
 
             const Transform3d& matrix = volume->get_matrix();
 
-            for (size_t i = 0; i < stl.v_shared.size(); ++i)
+            for (size_t i = 0; i < its.vertices.size(); ++i)
             {
                 stream << "     <" << VERTEX_TAG << " ";
-                Vec3f v = (matrix * stl.v_shared[i].cast<double>()).cast<float>();
+                Vec3f v = (matrix * its.vertices[i].cast<double>()).cast<float>();
                 stream << "x=\"" << v(0) << "\" ";
                 stream << "y=\"" << v(1) << "\" ";
                 stream << "z=\"" << v(2) << "\" />\n";
@@ -1920,19 +1916,19 @@ namespace Slic3r {
             VolumeToOffsetsMap::iterator volume_it = volumes_offsets.find(volume);
             assert(volume_it != volumes_offsets.end());
 
-            stl_file& stl = volume->mesh.stl;
+            const indexed_triangle_set &its = volume->mesh.its;
 
             // updates triangle offsets
             volume_it->second.first_triangle_id = triangles_count;
-            triangles_count += stl.stats.number_of_facets;
+            triangles_count += its.indices.size();
             volume_it->second.last_triangle_id = triangles_count - 1;
 
-            for (uint32_t i = 0; i < stl.stats.number_of_facets; ++i)
+            for (size_t i = 0; i < its.indices.size(); ++ i)
             {
                 stream << "     <" << TRIANGLE_TAG << " ";
                 for (int j = 0; j < 3; ++j)
                 {
-                    stream << "v" << j + 1 << "=\"" << stl.v_indices[i].vertex[j] + volume_it->second.first_vertex_id << "\" ";
+                    stream << "v" << j + 1 << "=\"" << its.indices[i].vertex[j] + volume_it->second.first_vertex_id << "\" ";
                 }
                 stream << "/>\n";
             }
diff --git a/src/libslic3r/Format/AMF.cpp b/src/libslic3r/Format/AMF.cpp
index e81ced3ad..dcd913864 100644
--- a/src/libslic3r/Format/AMF.cpp
+++ b/src/libslic3r/Format/AMF.cpp
@@ -923,23 +923,22 @@ bool store_amf(const char *path, Model *model, const DynamicPrintConfig *config)
         int              num_vertices = 0;
         for (ModelVolume *volume : object->volumes) {
             vertices_offsets.push_back(num_vertices);
-            if (! volume->mesh.repaired) 
+            if (! volume->mesh.repaired)
                 throw std::runtime_error("store_amf() requires repair()");
-            auto &stl = volume->mesh.stl;
-            if (stl.v_shared.empty())
-                stl_generate_shared_vertices(&stl);
+			volume->mesh.require_shared_vertices();
+            const indexed_triangle_set &its = volume->mesh.its;
             const Transform3d& matrix = volume->get_matrix();
-            for (size_t i = 0; i < stl.v_shared.size(); ++i) {
+            for (size_t i = 0; i < its.vertices.size(); ++i) {
                 stream << "         <vertex>\n";
                 stream << "           <coordinates>\n";
-                Vec3f v = (matrix * stl.v_shared[i].cast<double>()).cast<float>();
+                Vec3f v = (matrix * its.vertices[i].cast<double>()).cast<float>();
                 stream << "             <x>" << v(0) << "</x>\n";
                 stream << "             <y>" << v(1) << "</y>\n";
                 stream << "             <z>" << v(2) << "</z>\n";
                 stream << "           </coordinates>\n";
                 stream << "         </vertex>\n";
             }
-            num_vertices += stl.v_shared.size();
+            num_vertices += its.vertices.size();
         }
         stream << "      </vertices>\n";
         for (size_t i_volume = 0; i_volume < object->volumes.size(); ++i_volume) {
@@ -956,10 +955,10 @@ bool store_amf(const char *path, Model *model, const DynamicPrintConfig *config)
             if (volume->is_modifier())
                 stream << "        <metadata type=\"slic3r.modifier\">1</metadata>\n";
             stream << "        <metadata type=\"slic3r.volume_type\">" << ModelVolume::type_to_string(volume->type()) << "</metadata>\n";
-            for (int i = 0; i < (int)volume->mesh.stl.stats.number_of_facets; ++i) {
+            for (size_t i = 0; i < (int)volume->mesh.its.indices.size(); ++i) {
                 stream << "        <triangle>\n";
                 for (int j = 0; j < 3; ++j)
-                stream << "          <v" << j + 1 << ">" << volume->mesh.stl.v_indices[i].vertex[j] + vertices_offset << "</v" << j + 1 << ">\n";
+                stream << "          <v" << j + 1 << ">" << volume->mesh.its.indices[i].vertex[j] + vertices_offset << "</v" << j + 1 << ">\n";
                 stream << "        </triangle>\n";
             }
             stream << "      </volume>\n";
diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index 6da7fc0c3..770581c03 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -908,10 +908,11 @@ Polygon ModelObject::convex_hull_2d(const Transform3d &trafo_instance) const
     Points pts;
     for (const ModelVolume *v : this->volumes)
         if (v->is_model_part()) {
-            const stl_file &stl = v->mesh.stl;
             Transform3d trafo = trafo_instance * v->get_matrix();
-            if (stl.v_shared.empty()) {
+			const indexed_triangle_set &its = v->mesh.its;
+			if (its.vertices.empty()) {
                 // Using the STL faces.
+				const stl_file& stl = v->mesh.stl;
 				for (const stl_facet &facet : stl.facet_start)
                     for (size_t j = 0; j < 3; ++ j) {
                         Vec3d p = trafo * facet.vertex[j].cast<double>();
@@ -919,8 +920,8 @@ Polygon ModelObject::convex_hull_2d(const Transform3d &trafo_instance) const
                     }
             } else {
                 // Using the shared vertices should be a bit quicker than using the STL faces.
-                for (size_t i = 0; i < stl.v_shared.size(); ++ i) {
-                    Vec3d p = trafo * stl.v_shared[i].cast<double>();
+                for (size_t i = 0; i < its.vertices.size(); ++ i) {
+                    Vec3d p = trafo * its.vertices[i].cast<double>();
                     pts.emplace_back(coord_t(scale_(p.x())), coord_t(scale_(p.y())));
                 }
             }
diff --git a/src/libslic3r/TriangleMesh.cpp b/src/libslic3r/TriangleMesh.cpp
index 003affc27..ae35c8a5b 100644
--- a/src/libslic3r/TriangleMesh.cpp
+++ b/src/libslic3r/TriangleMesh.cpp
@@ -238,20 +238,20 @@ bool TriangleMesh::needed_repair() const
 
 void TriangleMesh::WriteOBJFile(const char* output_file)
 {
-    stl_generate_shared_vertices(&stl);
-    stl_write_obj(&stl, output_file);
+    stl_generate_shared_vertices(&stl, its);
+    its_write_obj(its, output_file);
 }
 
 void TriangleMesh::scale(float factor)
 {
     stl_scale(&(this->stl), factor);
-    stl_invalidate_shared_vertices(&this->stl);
+    this->its.clear();
 }
 
 void TriangleMesh::scale(const Vec3d &versor)
 {
     stl_scale_versor(&this->stl, versor.cast<float>());
-    stl_invalidate_shared_vertices(&this->stl);
+    this->its.clear();
 }
 
 void TriangleMesh::translate(float x, float y, float z)
@@ -259,7 +259,7 @@ void TriangleMesh::translate(float x, float y, float z)
     if (x == 0.f && y == 0.f && z == 0.f)
         return;
     stl_translate_relative(&(this->stl), x, y, z);
-    stl_invalidate_shared_vertices(&this->stl);
+    this->its.clear();
 }
 
 void TriangleMesh::translate(const Vec3f &displacement)
@@ -282,7 +282,7 @@ void TriangleMesh::rotate(float angle, const Axis &axis)
     } else if (axis == Z) {
         stl_rotate_z(&(this->stl), angle);
     }
-    stl_invalidate_shared_vertices(&this->stl);
+    this->its.clear();
 }
 
 void TriangleMesh::rotate(float angle, const Vec3d& axis)
@@ -305,13 +305,13 @@ void TriangleMesh::mirror(const Axis &axis)
     } else if (axis == Z) {
         stl_mirror_xy(&this->stl);
     }
-    stl_invalidate_shared_vertices(&this->stl);
+    this->its.clear();
 }
 
 void TriangleMesh::transform(const Transform3d& t, bool fix_left_handed)
 {
     stl_transform(&stl, t);
-    stl_invalidate_shared_vertices(&stl);
+    this->its.clear();
 	if (fix_left_handed && t.matrix().block(0, 0, 3, 3).determinant() < 0.) {
 		// Left handed transformation is being applied. It is a good idea to flip the faces and their normals.
 		this->repair();
@@ -322,7 +322,7 @@ void TriangleMesh::transform(const Transform3d& t, bool fix_left_handed)
 void TriangleMesh::transform(const Matrix3d& m, bool fix_left_handed)
 {
     stl_transform(&stl, m);
-    stl_invalidate_shared_vertices(&stl);
+    this->its.clear();
     if (fix_left_handed && m.determinant() < 0.) {
         // Left handed transformation is being applied. It is a good idea to flip the faces and their normals.
         this->repair();
@@ -443,7 +443,7 @@ void TriangleMesh::merge(const TriangleMesh &mesh)
 {
     // reset stats and metadata
     int number_of_facets = this->stl.stats.number_of_facets;
-    stl_invalidate_shared_vertices(&this->stl);
+    this->its.clear();
     this->repaired = false;
     
     // update facet count and allocate more memory
@@ -484,9 +484,9 @@ Polygon TriangleMesh::convex_hull()
 {
     this->require_shared_vertices();
     Points pp;
-    pp.reserve(this->stl.v_shared.size());
-    for (size_t i = 0; i < this->stl.v_shared.size(); ++ i) {
-        const stl_vertex &v = this->stl.v_shared[i];
+    pp.reserve(this->its.vertices.size());
+    for (size_t i = 0; i < this->its.vertices.size(); ++ i) {
+        const stl_vertex &v = this->its.vertices[i];
         pp.emplace_back(Point::new_scale(v(0), v(1)));
     }
     return Slic3r::Geometry::convex_hull(pp);
@@ -504,14 +504,14 @@ BoundingBoxf3 TriangleMesh::bounding_box() const
 BoundingBoxf3 TriangleMesh::transformed_bounding_box(const Transform3d &trafo) const
 {
     BoundingBoxf3 bbox;
-    if (stl.v_shared.empty()) {
+    if (this->its.vertices.empty()) {
         // Using the STL faces.
 		for (const stl_facet &facet : this->stl.facet_start)
             for (size_t j = 0; j < 3; ++ j)
                 bbox.merge(trafo * facet.vertex[j].cast<double>());
     } else {
         // Using the shared vertices should be a bit quicker than using the STL faces.
-		for (const stl_vertex &v : this->stl.v_shared)
+		for (const stl_vertex &v : this->its.vertices)
             bbox.merge(trafo * v.cast<double>());
     }
     return bbox;
@@ -576,11 +576,11 @@ void TriangleMesh::require_shared_vertices()
     assert(stl_validate(&this->stl));
     if (! this->repaired) 
         this->repair();
-    if (this->stl.v_shared.empty()) {
+    if (this->its.vertices.empty()) {
         BOOST_LOG_TRIVIAL(trace) << "TriangleMeshSlicer::require_shared_vertices - stl_generate_shared_vertices";
-        stl_generate_shared_vertices(&(this->stl));
+        stl_generate_shared_vertices(&this->stl, this->its);
     }
-    assert(stl_validate(&this->stl));
+    assert(stl_validate(&this->stl, this->its));
     BOOST_LOG_TRIVIAL(trace) << "TriangleMeshSlicer::require_shared_vertices - end";
 }
 
@@ -592,9 +592,9 @@ void TriangleMeshSlicer::init(const TriangleMesh *_mesh, throw_on_cancel_callbac
 
     throw_on_cancel();
     facets_edges.assign(_mesh->stl.stats.number_of_facets * 3, -1);
-	v_scaled_shared.assign(_mesh->stl.v_shared.size(), stl_vertex());
+	v_scaled_shared.assign(_mesh->its.vertices.size(), stl_vertex());
 	for (size_t i = 0; i < v_scaled_shared.size(); ++ i)
-        this->v_scaled_shared[i] = _mesh->stl.v_shared[i] / float(SCALING_FACTOR);
+        this->v_scaled_shared[i] = _mesh->its.vertices[i] / float(SCALING_FACTOR);
 
     // Create a mapping from triangle edge into face.
     struct EdgeToFace {
@@ -614,8 +614,8 @@ void TriangleMeshSlicer::init(const TriangleMesh *_mesh, throw_on_cancel_callbac
     for (uint32_t facet_idx = 0; facet_idx < this->mesh->stl.stats.number_of_facets; ++ facet_idx)
         for (int i = 0; i < 3; ++ i) {
             EdgeToFace &e2f = edges_map[facet_idx*3+i];
-            e2f.vertex_low  = this->mesh->stl.v_indices[facet_idx].vertex[i];
-            e2f.vertex_high = this->mesh->stl.v_indices[facet_idx].vertex[(i + 1) % 3];
+            e2f.vertex_low  = this->mesh->its.indices[facet_idx].vertex[i];
+            e2f.vertex_high = this->mesh->its.indices[facet_idx].vertex[(i + 1) % 3];
             e2f.face        = facet_idx;
             // 1 based indexing, to be always strictly positive.
             e2f.face_edge   = i + 1;
@@ -852,7 +852,7 @@ TriangleMeshSlicer::FacetSliceType TriangleMeshSlicer::slice_facet(
     // Reorder vertices so that the first one is the one with lowest Z.
     // This is needed to get all intersection lines in a consistent order
     // (external on the right of the line)
-    const int *vertices = this->mesh->stl.v_indices[facet_idx].vertex;
+    const int *vertices = this->mesh->its.indices[facet_idx].vertex;
     int i = (facet.vertex[1].z() == min_z) ? 1 : ((facet.vertex[2].z() == min_z) ? 2 : 0);
 
     // These are used only if the cut plane is tilted:
diff --git a/src/libslic3r/TriangleMesh.hpp b/src/libslic3r/TriangleMesh.hpp
index c16f4a664..75082cfdb 100644
--- a/src/libslic3r/TriangleMesh.hpp
+++ b/src/libslic3r/TriangleMesh.hpp
@@ -69,12 +69,13 @@ public:
     void reset_repair_stats();
     bool needed_repair() const;
     void require_shared_vertices();
-    bool   has_shared_vertices() const { return ! stl.v_shared.empty(); }
+    bool   has_shared_vertices() const { return ! this->its.vertices.empty(); }
     size_t facets_count() const { return this->stl.stats.number_of_facets; }
     bool   empty() const { return this->facets_count() == 0; }
     bool is_splittable() const;
 
     stl_file stl;
+    indexed_triangle_set its;
     bool repaired;
 
 private:
diff --git a/src/slic3r/GUI/PresetBundle.cpp b/src/slic3r/GUI/PresetBundle.cpp
index fb3b6f7a4..45092f257 100644
--- a/src/slic3r/GUI/PresetBundle.cpp
+++ b/src/slic3r/GUI/PresetBundle.cpp
@@ -781,7 +781,7 @@ void PresetBundle::load_config_file_config(const std::string &name_or_path, bool
                     if (i == 0)
                         suffix[0] = 0;
                     else
-                        sprintf(suffix, "%d", i);
+                        sprintf(suffix, "%d", (int)i);
                     std::string new_name = name + suffix;
                     loaded = &this->filaments.load_preset(this->filaments.path_from_name(new_name),
                         new_name, std::move(cfg), i == 0);
@@ -1379,7 +1379,7 @@ void PresetBundle::export_configbundle(const std::string &path, bool export_syst
     for (size_t i = 0; i < this->filament_presets.size(); ++ i) {
         char suffix[64];
         if (i > 0)
-            sprintf(suffix, "_%d", i);
+            sprintf(suffix, "_%d", (int)i);
         else
             suffix[0] = 0;
         c << "filament" << suffix << " = " << this->filament_presets[i] << std::endl;
diff --git a/xs/xsp/TriangleMesh.xsp b/xs/xsp/TriangleMesh.xsp
index 53b052027..3e90bfefd 100644
--- a/xs/xsp/TriangleMesh.xsp
+++ b/xs/xsp/TriangleMesh.xsp
@@ -98,20 +98,18 @@ SV*
 TriangleMesh::vertices()
     CODE:
         if (!THIS->repaired) CONFESS("vertices() requires repair()");
-        
-        if (THIS->stl.v_shared.empty())
-            stl_generate_shared_vertices(&(THIS->stl));
+        THIS->require_shared_vertices();
         
         // vertices
         AV* vertices = newAV();
-        av_extend(vertices, THIS->stl.v_shared.size());
-        for (size_t i = 0; i < THIS->stl.v_shared.size(); i++) {
+        av_extend(vertices, THIS->its.vertices.size());
+        for (size_t i = 0; i < THIS->its.vertices.size(); i++) {
             AV* vertex = newAV();
             av_store(vertices, i, newRV_noinc((SV*)vertex));
             av_extend(vertex, 2);
-            av_store(vertex, 0, newSVnv(THIS->stl.v_shared[i](0)));
-            av_store(vertex, 1, newSVnv(THIS->stl.v_shared[i](1)));
-            av_store(vertex, 2, newSVnv(THIS->stl.v_shared[i](2)));
+            av_store(vertex, 0, newSVnv(THIS->its.vertices[i](0)));
+            av_store(vertex, 1, newSVnv(THIS->its.vertices[i](1)));
+            av_store(vertex, 2, newSVnv(THIS->its.vertices[i](2)));
         }
         
         RETVAL = newRV_noinc((SV*)vertices);
@@ -122,9 +120,7 @@ SV*
 TriangleMesh::facets()
     CODE:
         if (!THIS->repaired) CONFESS("facets() requires repair()");
-        
-        if (THIS->stl.v_shared.empty())
-            stl_generate_shared_vertices(&(THIS->stl));
+        THIS->require_shared_vertices();
         
         // facets
         AV* facets = newAV();
@@ -133,9 +129,9 @@ TriangleMesh::facets()
             AV* facet = newAV();
             av_store(facets, i, newRV_noinc((SV*)facet));
             av_extend(facet, 2);
-            av_store(facet, 0, newSVnv(THIS->stl.v_indices[i].vertex[0]));
-            av_store(facet, 1, newSVnv(THIS->stl.v_indices[i].vertex[1]));
-            av_store(facet, 2, newSVnv(THIS->stl.v_indices[i].vertex[2]));
+            av_store(facet, 0, newSVnv(THIS->its.indices[i].vertex[0]));
+            av_store(facet, 1, newSVnv(THIS->its.indices[i].vertex[1]));
+            av_store(facet, 2, newSVnv(THIS->its.indices[i].vertex[2]));
         }
         
         RETVAL = newRV_noinc((SV*)facets);