diff --git a/Extras/obj2sdf/obj2sdf.cpp b/Extras/obj2sdf/obj2sdf.cpp
index 488b24d54..6bd3cf948 100644
--- a/Extras/obj2sdf/obj2sdf.cpp
+++ b/Extras/obj2sdf/obj2sdf.cpp
@@ -13,6 +13,22 @@
 #include "Bullet3Common/b3FileUtils.h"
 #include "../Utils/b3ResourcePath.h"
 #include "Bullet3Common/b3CommandLineArgs.h"
+#include "Bullet3Common/b3HashMap.h"
+
+struct ShapeContainer
+{
+	std::string m_matName;
+	std::string m_shapeName;
+	tinyobj::material_t material;
+	std::vector<float>          positions;
+	std::vector<float>          normals;
+	std::vector<float>          texcoords;
+	std::vector<unsigned int>   indices;
+
+	b3AlignedObjectArray<int> m_shapeIndices;
+};
+
+b3HashMap<b3HashString, ShapeContainer> gMaterialNames;
 
 #define MAX_PATH_LEN 1024
 
@@ -53,6 +69,8 @@ int main(int argc, char* argv[])
 		printf("Please use --fileName=\"pathToObj\".");
 		exit(0);
 	}
+	bool mergeMaterials = args.CheckCmdLineFlag("mergeMaterials");
+	
 	char fileNameWithPath[MAX_PATH_LEN];
 	bool fileFound = (b3ResourcePath::findResourcePath(fileName,fileNameWithPath,MAX_PATH_LEN))>0;
 	char materialPrefixPath[MAX_PATH_LEN];
@@ -72,141 +90,359 @@ int main(int argc, char* argv[])
 
 	fprintf(sdfFile, "<sdf version='1.6'>\n\t<world name='default'>\n\t<gravity>0 0 -9.8</gravity>\n");
 
-	for (int s=0;s<(int)shapes.size();s++)
+	for (int s = 0; s < (int)shapes.size(); s++)
 	{
 		tinyobj::shape_t& shape = shapes[s];
-
-		if (shape.name.length())
-		{
-			printf("object name = %s\n", shape.name.c_str());
-		}
-
-		char objFileName[MAX_PATH_LEN];
-		if (strlen(materialPrefixPath)>0)
-		{
-			sprintf(objFileName,"%s/part%d.obj",materialPrefixPath,s);
-		} else
-		{
-			sprintf(objFileName,"part%d.obj",s);
-		}
-		FILE* f = fopen(objFileName,"w");
-		if (f==0)
-		{
-			printf("Fatal error: cannot create part obj file %s\n",objFileName);
-			exit(0);
-		}
-		fprintf(f,"# Exported using automatic converter by Erwin Coumans\n");
-		if (matLibName.length())
-		{
-			fprintf(f,"mtllib %s.mtl\n", matLibName.c_str());
-		} else
-		{
-			fprintf(f,"mtllib bedroom.mtl\n");
-
-		}
-
-
-		int faceCount = shape.mesh.indices.size();
-		int vertexCount = shape.mesh.positions.size();
 		tinyobj::material_t mat = shape.material;
-		if (shape.name.length())
-		{
-			const char* objName = shape.name.c_str();
-			printf("mat.name = %s\n", objName);
-			fprintf(f,"#object %s\n\n",objName);
-		}
-		for (int v=0;v<vertexCount/3;v++)
-		{
-			fprintf(f,"v %f %f %f\n",shape.mesh.positions[v*3+0],shape.mesh.positions[v*3+1],shape.mesh.positions[v*3+2]);
-		}
 		
-		if (mat.name.length())
+		b3HashString key = mat.name.length() ? mat.name.c_str() : "";
+		if (!gMaterialNames.find(key))
 		{
-			fprintf(f,"usemtl %s\n",mat.name.c_str());
-		} else
-		{
-			fprintf(f,"usemtl wire_028089177\n");
+			ShapeContainer container;
+			container.m_matName = mat.name;
+			container.m_shapeName = shape.name;
+			container.material = mat;
+			gMaterialNames.insert(key, container);
 		}
 
-		fprintf(f,"\n");
-		int numNormals = int(shape.mesh.normals.size());
-
-		for (int vn = 0;vn<numNormals/3;vn++)
+		ShapeContainer* shapeC = gMaterialNames.find(key);
+		if (shapeC)
 		{
-			fprintf(f,"vn %f %f %f\n",shape.mesh.normals[vn*3+0],shape.mesh.normals[vn*3+1],shape.mesh.normals[vn*3+2]);
-		}
+			shapeC->m_shapeIndices.push_back(s);
+		
+			int curPositions = shapeC->positions.size()/3;
+			int curNormals = shapeC->normals.size()/3;
+			int curTexcoords = shapeC->texcoords.size()/2;
 
-		fprintf(f,"\n");
-		int numTexCoords = int(shape.mesh.texcoords.size());
-		for (int vt = 0;vt<numTexCoords/2;vt++)
-		{
-			fprintf(f,"vt %f %f\n",shape.mesh.texcoords[vt*2+0],shape.mesh.texcoords[vt*2+1]);
-		}
-
-		fprintf(f,"s off\n");
-
-		for (int face=0;face<faceCount;face+=3)
-		{
-			if (face<0 && face>=int(shape.mesh.indices.size()))
+			int faceCount = shape.mesh.indices.size();
+			int vertexCount = shape.mesh.positions.size();
+			for (int v = 0; v < vertexCount; v++)
 			{
-				continue;
+				shapeC->positions.push_back(shape.mesh.positions[v]);
+			}
+			int numNormals = int(shape.mesh.normals.size());
+			for (int vn = 0; vn < numNormals; vn++)
+			{
+				shapeC->normals.push_back(shape.mesh.normals[vn]);
+			}
+			int numTexCoords = int(shape.mesh.texcoords.size());
+			for (int vt = 0; vt < numTexCoords; vt++)
+			{
+				shapeC->texcoords.push_back(shape.mesh.texcoords[vt]);
+			}
+
+			for (int face = 0; face < faceCount; face += 3)
+			{
+				if (face < 0 && face >= int(shape.mesh.indices.size()))
+				{
+					continue;
+				}
+
+				shapeC->indices.push_back(shape.mesh.indices[face] + curPositions);
+				shapeC->indices.push_back(shape.mesh.indices[face+1] + curPositions);
+				shapeC->indices.push_back(shape.mesh.indices[face + 2] + curPositions);
 			}
-			fprintf(f,"f %d/%d/%d %d/%d/%d %d/%d/%d\n", 
-				shape.mesh.indices[face]+1,shape.mesh.indices[face]+1,shape.mesh.indices[face]+1,
-				shape.mesh.indices[face+1]+1,shape.mesh.indices[face+1]+1,shape.mesh.indices[face+1]+1,
-				shape.mesh.indices[face+2]+1,shape.mesh.indices[face+2]+1,shape.mesh.indices[face+2]+1);
 		}
-		fclose(f);
+	}
+	
+	printf("unique materials=%d\n", gMaterialNames.size());
 
-		float kdRed=mat.diffuse[0];
-		float kdGreen=mat.diffuse[1];
-		float kdBlue=mat.diffuse[2];
+	
+	if (mergeMaterials)
+	{
+		for (int m = 0; m < gMaterialNames.size();m++)
+		{
+			if (gMaterialNames.getAtIndex(m)->m_shapeIndices.size() == 0)
+				continue;
 
-		char objSdfPartFileName[MAX_PATH_LEN];
-		sprintf(objSdfPartFileName,"part%d.obj",s);
-		fprintf(sdfFile,"\t\t<model name='%s'>\n"
-     "\t\t\t<static>1</static>\n"
-      "\t\t\t<pose frame=''>0 0 0 0 0 0</pose>\n"
-      "\t\t\t<link name='link_d%d'>\n"
-        "\t\t\t<inertial>\n"
-          "\t\t\t<mass>0</mass>\n"
-          "\t\t\t<inertia>\n"
-            "\t\t\t<ixx>0.166667</ixx>\n"
-            "\t\t\t<ixy>0</ixy>\n"
-            "\t\t\t<ixz>0</ixz>\n"
-            "\t\t\t<iyy>0.166667</iyy>\n"
-            "\t\t\t<iyz>0</iyz>\n"
-            "\t\t\t<izz>0.166667</izz>\n"
-          "\t\t\t</inertia>\n"
-       "\t\t\t</inertial>\n"
-        "\t\t\t<collision name='collision_%d'>\n"
-         "\t\t\t<geometry>\n"
-            "\t\t\t<mesh>\n"
-           "\t\t\t<scale>1 1 1</scale>\n"
-           "\t\t\t\t<uri>%s</uri>\n"
-         "\t\t\t</mesh>\n"
-          "\t\t\t</geometry>\n"
-      "\t\t\t  </collision>\n"
-       "\t\t\t<visual name='visual'>\n"
-         "\t\t\t\t<geometry>\n"
-         "\t\t\t\t<mesh>\n"
-           "\t\t\t\t\t<scale>1 1 1</scale>\n"
-           "\t\t\t\t\t<uri>%s</uri>\n"
-         "\t\t\t\t</mesh>\n"
-       "\t\t\t\t</geometry>\n"
-			"\t\t\t<material>\n"
-          "\t\t\t\t<ambient>1 0 0 1</ambient>\n"
-          "\t\t\t\t<diffuse>%f %f %f 1</diffuse>\n"
-          "\t\t\t\t<specular>0.1 0.1 0.1 1</specular>\n"
-          "\t\t\t\t<emissive>0 0 0 0</emissive>\n"
-        "\t\t\t </material>\n"
-       "\t\t\t </visual>\n"
-     "\t\t\t </link>\n"
-    "\t\t\t</model>\n",objSdfPartFileName,s,s,
-			objSdfPartFileName,objSdfPartFileName, 
-			kdRed, kdGreen, kdBlue);
+			ShapeContainer* shapeCon =gMaterialNames.getAtIndex(m);
+			
+			printf("object name = %s\n", shapeCon->m_shapeName.c_str());
+			
+			char objSdfPartFileName[MAX_PATH_LEN];
+			sprintf(objSdfPartFileName, "part%d.obj", m);
+
+			char objFileName[MAX_PATH_LEN];
+			if (strlen(materialPrefixPath) > 0)
+			{
+				sprintf(objFileName, "%s/part%d.obj", materialPrefixPath, m);
+			}
+			else
+			{
+				sprintf(objFileName, "part%d.obj", m);
+			}
 
 
+			FILE* f = fopen(objFileName, "w");
+			if (f == 0)
+			{
+				printf("Fatal error: cannot create part obj file %s\n", objFileName);
+				exit(0);
+			}
+			fprintf(f, "# Exported using automatic converter by Erwin Coumans\n");
+			if (matLibName.length())
+			{
+				fprintf(f, "mtllib %s.mtl\n", matLibName.c_str());
+			}
+			else
+			{
+				fprintf(f, "mtllib bedroom.mtl\n");
+
+			}
+
+			int faceCount = shapeCon->indices.size();
+			int vertexCount = shapeCon->positions.size();
+			tinyobj::material_t mat = shapeCon->material;
+			if (shapeCon->m_matName.length())
+			{
+				const char* objName = shapeCon->m_matName.c_str();
+				printf("mat.name = %s\n", objName);
+				fprintf(f, "#object %s\n\n", objName);
+			}
+			for (int v = 0; v < vertexCount / 3; v++)
+			{
+				fprintf(f, "v %f %f %f\n", shapeCon->positions[v * 3 + 0], shapeCon->positions[v * 3 + 1], shapeCon->positions[v * 3 + 2]);
+			}
+
+			if (mat.name.length())
+			{
+				fprintf(f, "usemtl %s\n", mat.name.c_str());
+			}
+			else
+			{
+				fprintf(f, "usemtl wire_028089177\n");
+			}
+
+			fprintf(f, "\n");
+			int numNormals = int(shapeCon->normals.size());
+
+			for (int vn = 0; vn < numNormals / 3; vn++)
+			{
+				fprintf(f, "vn %f %f %f\n", shapeCon->normals[vn * 3 + 0], shapeCon->normals[vn * 3 + 1], shapeCon->normals[vn * 3 + 2]);
+			}
+
+			fprintf(f, "\n");
+			int numTexCoords = int(shapeCon->texcoords.size());
+			for (int vt = 0; vt < numTexCoords / 2; vt++)
+			{
+				fprintf(f, "vt %f %f\n", shapeCon->texcoords[vt * 2 + 0], shapeCon->texcoords[vt * 2 + 1]);
+			}
+
+			fprintf(f, "s off\n");
+
+			for (int face = 0; face < faceCount; face += 3)
+			{
+				if (face < 0 && face >= int(shapeCon->indices.size()))
+				{
+					continue;
+				}
+				fprintf(f, "f %d/%d/%d %d/%d/%d %d/%d/%d\n",
+					shapeCon->indices[face] + 1, shapeCon->indices[face] + 1, shapeCon->indices[face] + 1,
+					shapeCon->indices[face + 1] + 1, shapeCon->indices[face + 1] + 1, shapeCon->indices[face + 1] + 1,
+					shapeCon->indices[face + 2] + 1, shapeCon->indices[face + 2] + 1, shapeCon->indices[face + 2] + 1);
+			}
+			fclose(f);
+
+			float kdRed = mat.diffuse[0];
+			float kdGreen = mat.diffuse[1];
+			float kdBlue = mat.diffuse[2];
+			float transparency = mat.transparency;
+			
+			fprintf(sdfFile, "\t\t<model name='%s'>\n"
+				"\t\t\t<static>1</static>\n"
+				"\t\t\t<pose frame=''>0 0 0 0 0 0</pose>\n"
+				"\t\t\t<link name='link_d%d'>\n"
+				"\t\t\t<inertial>\n"
+				"\t\t\t<mass>0</mass>\n"
+				"\t\t\t<inertia>\n"
+				"\t\t\t<ixx>0.166667</ixx>\n"
+				"\t\t\t<ixy>0</ixy>\n"
+				"\t\t\t<ixz>0</ixz>\n"
+				"\t\t\t<iyy>0.166667</iyy>\n"
+				"\t\t\t<iyz>0</iyz>\n"
+				"\t\t\t<izz>0.166667</izz>\n"
+				"\t\t\t</inertia>\n"
+				"\t\t\t</inertial>\n"
+				"\t\t\t<collision concave='yes' name='collision_%d'>\n"
+				"\t\t\t<geometry>\n"
+				"\t\t\t<mesh>\n"
+				"\t\t\t<scale>1 1 1</scale>\n"
+				"\t\t\t\t<uri>%s</uri>\n"
+				"\t\t\t</mesh>\n"
+				"\t\t\t</geometry>\n"
+				"\t\t\t  </collision>\n"
+				"\t\t\t<visual name='visual'>\n"
+				"\t\t\t\t<geometry>\n"
+				"\t\t\t\t<mesh>\n"
+				"\t\t\t\t\t<scale>1 1 1</scale>\n"
+				"\t\t\t\t\t<uri>%s</uri>\n"
+				"\t\t\t\t</mesh>\n"
+				"\t\t\t\t</geometry>\n"
+				"\t\t\t<material>\n"
+				"\t\t\t\t<ambient>1 0 0 1</ambient>\n"
+				"\t\t\t\t<diffuse>%f %f %f %f</diffuse>\n"
+				"\t\t\t\t<specular>0.1 0.1 0.1 1</specular>\n"
+				"\t\t\t\t<emissive>0 0 0 0</emissive>\n"
+				"\t\t\t </material>\n"
+				"\t\t\t </visual>\n"
+				"\t\t\t </link>\n"
+				"\t\t\t</model>\n", objSdfPartFileName, m, m,
+				objSdfPartFileName, objSdfPartFileName,
+				kdRed, kdGreen, kdBlue, transparency);
+
+
+		}
+
+
+
+
+
+
+
+
+	}
+	else
+	{
+
+		for (int s = 0; s < (int)shapes.size(); s++)
+		{
+			tinyobj::shape_t& shape = shapes[s];
+
+			if (shape.name.length())
+			{
+				printf("object name = %s\n", shape.name.c_str());
+			}
+
+			char objFileName[MAX_PATH_LEN];
+			if (strlen(materialPrefixPath) > 0)
+			{
+				sprintf(objFileName, "%s/part%d.obj", materialPrefixPath, s);
+			}
+			else
+			{
+				sprintf(objFileName, "part%d.obj", s);
+			}
+			FILE* f = fopen(objFileName, "w");
+			if (f == 0)
+			{
+				printf("Fatal error: cannot create part obj file %s\n", objFileName);
+				exit(0);
+			}
+			fprintf(f, "# Exported using automatic converter by Erwin Coumans\n");
+			if (matLibName.length())
+			{
+				fprintf(f, "mtllib %s.mtl\n", matLibName.c_str());
+			}
+			else
+			{
+				fprintf(f, "mtllib bedroom.mtl\n");
+
+			}
+
+
+			int faceCount = shape.mesh.indices.size();
+			int vertexCount = shape.mesh.positions.size();
+			tinyobj::material_t mat = shape.material;
+			if (shape.name.length())
+			{
+				const char* objName = shape.name.c_str();
+				printf("mat.name = %s\n", objName);
+				fprintf(f, "#object %s\n\n", objName);
+			}
+			for (int v = 0; v < vertexCount / 3; v++)
+			{
+				fprintf(f, "v %f %f %f\n", shape.mesh.positions[v * 3 + 0], shape.mesh.positions[v * 3 + 1], shape.mesh.positions[v * 3 + 2]);
+			}
+
+			if (mat.name.length())
+			{
+				fprintf(f, "usemtl %s\n", mat.name.c_str());
+			}
+			else
+			{
+				fprintf(f, "usemtl wire_028089177\n");
+			}
+
+			fprintf(f, "\n");
+			int numNormals = int(shape.mesh.normals.size());
+
+			for (int vn = 0; vn < numNormals / 3; vn++)
+			{
+				fprintf(f, "vn %f %f %f\n", shape.mesh.normals[vn * 3 + 0], shape.mesh.normals[vn * 3 + 1], shape.mesh.normals[vn * 3 + 2]);
+			}
+
+			fprintf(f, "\n");
+			int numTexCoords = int(shape.mesh.texcoords.size());
+			for (int vt = 0; vt < numTexCoords / 2; vt++)
+			{
+				fprintf(f, "vt %f %f\n", shape.mesh.texcoords[vt * 2 + 0], shape.mesh.texcoords[vt * 2 + 1]);
+			}
+
+			fprintf(f, "s off\n");
+
+			for (int face = 0; face < faceCount; face += 3)
+			{
+				if (face < 0 && face >= int(shape.mesh.indices.size()))
+				{
+					continue;
+				}
+				fprintf(f, "f %d/%d/%d %d/%d/%d %d/%d/%d\n",
+					shape.mesh.indices[face] + 1, shape.mesh.indices[face] + 1, shape.mesh.indices[face] + 1,
+					shape.mesh.indices[face + 1] + 1, shape.mesh.indices[face + 1] + 1, shape.mesh.indices[face + 1] + 1,
+					shape.mesh.indices[face + 2] + 1, shape.mesh.indices[face + 2] + 1, shape.mesh.indices[face + 2] + 1);
+			}
+			fclose(f);
+
+			float kdRed = mat.diffuse[0];
+			float kdGreen = mat.diffuse[1];
+			float kdBlue = mat.diffuse[2];
+			float transparency = mat.transparency;
+			char objSdfPartFileName[MAX_PATH_LEN];
+			sprintf(objSdfPartFileName, "part%d.obj", s);
+			fprintf(sdfFile, "\t\t<model name='%s'>\n"
+				"\t\t\t<static>1</static>\n"
+				"\t\t\t<pose frame=''>0 0 0 0 0 0</pose>\n"
+				"\t\t\t<link name='link_d%d'>\n"
+				"\t\t\t<inertial>\n"
+				"\t\t\t<mass>0</mass>\n"
+				"\t\t\t<inertia>\n"
+				"\t\t\t<ixx>0.166667</ixx>\n"
+				"\t\t\t<ixy>0</ixy>\n"
+				"\t\t\t<ixz>0</ixz>\n"
+				"\t\t\t<iyy>0.166667</iyy>\n"
+				"\t\t\t<iyz>0</iyz>\n"
+				"\t\t\t<izz>0.166667</izz>\n"
+				"\t\t\t</inertia>\n"
+				"\t\t\t</inertial>\n"
+				"\t\t\t<collision name='collision_%d'>\n"
+				"\t\t\t<geometry>\n"
+				"\t\t\t<mesh>\n"
+				"\t\t\t<scale>1 1 1</scale>\n"
+				"\t\t\t\t<uri>%s</uri>\n"
+				"\t\t\t</mesh>\n"
+				"\t\t\t</geometry>\n"
+				"\t\t\t  </collision>\n"
+				"\t\t\t<visual name='visual'>\n"
+				"\t\t\t\t<geometry>\n"
+				"\t\t\t\t<mesh>\n"
+				"\t\t\t\t\t<scale>1 1 1</scale>\n"
+				"\t\t\t\t\t<uri>%s</uri>\n"
+				"\t\t\t\t</mesh>\n"
+				"\t\t\t\t</geometry>\n"
+				"\t\t\t<material>\n"
+				"\t\t\t\t<ambient>1 0 0 1</ambient>\n"
+				"\t\t\t\t<diffuse>%f %f %f %f</diffuse>\n"
+				"\t\t\t\t<specular>0.1 0.1 0.1 1</specular>\n"
+				"\t\t\t\t<emissive>0 0 0 0</emissive>\n"
+				"\t\t\t </material>\n"
+				"\t\t\t </visual>\n"
+				"\t\t\t </link>\n"
+				"\t\t\t</model>\n", objSdfPartFileName, s, s,
+				objSdfPartFileName, objSdfPartFileName,
+				kdRed, kdGreen, kdBlue, transparency);
+
+
+		}
 	}
 	fprintf(sdfFile,"\t</world>\n</sdf>\n");
 
diff --git a/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.cpp b/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.cpp
index d8e3102a8..129f5683a 100644
--- a/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.cpp
+++ b/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.cpp
@@ -328,6 +328,7 @@ void InitMaterial(material_t& material) {
     material.emission[i] = 0.f;
   }
   material.shininess = 1.f;
+  material.transparency = 1.f;
 }
 
 std::string LoadMtl (
@@ -465,6 +466,20 @@ std::string LoadMtl (
       continue;
     }
 
+	// transparency
+	if (token[0] == 'T' && token[1] == 'r' && isSpace(token[2])) {
+		token += 2;
+		material.transparency = parseFloat(token);
+		continue;
+	}
+
+	// transparency
+	if (token[0] == 'd' && isSpace(token[1])) {
+		token += 1;
+		material.transparency = parseFloat(token);
+		continue;
+	}
+
     // ambient texture
     if ((0 == strncmp(token, "map_Ka", 6)) && isSpace(token[6])) {
       token += 7;
diff --git a/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.h b/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.h
index bc3ad2eb7..16f918c46 100644
--- a/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.h
+++ b/examples/ThirdPartyLibs/Wavefront/tiny_obj_loader.h
@@ -22,6 +22,7 @@ typedef struct
     float transmittance[3];
     float emission[3];
     float shininess;
+	float transparency;
 
     std::string ambient_texname;
     std::string diffuse_texname;