Read normals and textures from OBJ, do not duplicate vertices.

PiperOrigin-RevId: 510461549
Change-Id: I19245d691e722a8371e61153383f275f599353d6

test/user/testdata/mesh.xml

@@ -0,0 +1,8 @@
+<mujoco>
+  <asset>
+    <mesh file="cube.msh"/>
+  </asset>
+  <worldbody>
+    <geom type="mesh" mesh="cube"/>
+  </worldbody>
+</mujoco>

test/user/user_mesh_test.cc

@@ -32,6 +32,8 @@ namespace {
 
 using MjCMeshTest = MujocoTest;
 
+static const char* const kMeshPath =
+    "user/testdata/mesh.xml";
 static const char* const kDuplicateVerticesPath =
     "user/testdata/duplicate_vertices.xml";
 static const char* const kCubePath =
@@ -100,6 +102,17 @@ TEST_F(MjCMeshTest, DeDuplicateSTLVertices) {
   mj_deleteModel(model);
 }
 
+// ------------- test Mesh loading (MSH) ------------------------------
+TEST_F(MjCMeshTest, LoadMSH) {
+  const std::string xml_path = GetTestDataFilePath(kMeshPath);
+  char error[1024];
+  size_t error_sz = 1024;
+  mjModel* model = mj_loadXML(xml_path.c_str(), 0, error, error_sz);
+  ASSERT_THAT(model, testing::NotNull()) << error;
+  ASSERT_EQ(model->nmeshvert, 36);
+  mj_deleteModel(model);
+}
+
 // ------------- test OBJ loading ----------------------------------------------
 
 using MjCMeshTest = MujocoTest;
@@ -109,6 +122,7 @@ TEST_F(MjCMeshTest, LoadCube) {
   mjModel* model = mj_loadXML(xml_path.c_str(), 0, nullptr, 0);
   ASSERT_GT(model->ngeom, 0);
   ASSERT_EQ(model->nmeshvert, 8);
+  ASSERT_EQ(model->nmeshface, 12);
   mj_deleteModel(model);
 }
 
@@ -146,7 +160,7 @@ TEST_F(MjCMeshTest, KeepDuplicateOBJVertices) {
   char error[1024];
   size_t error_sz = 1024;
   mjModel* model = mj_loadXML(xml_path.c_str(), 0, error, error_sz);
-  ASSERT_EQ(model->nmeshvert, 12);
+  ASSERT_EQ(model->nmeshvert, 16);
   mj_deleteModel(model);
 }
 
@@ -175,6 +189,26 @@ TEST_F(MjCMeshTest, TinyMeshLoads) {
   mj_deleteModel(model);
 }
 
+// ------------- test inline loading ------------------------------------------
+TEST_F(MjCMeshTest, FaceNormalAutogenerated) {
+  static constexpr char xml[] = R"(
+  <mujoco>
+    <asset>
+      <mesh name="example_mesh"
+        vertex="0 0 0  1 0 0  0 1 0  0 0 1"
+        normal="1 0 0  0 1 0  0 0 1  0.707 0 0.707"
+        face="0 2 1  0 3 2" />
+    </asset>
+    <worldbody>
+      <geom type="mesh" mesh="example_mesh"/>
+    </worldbody>
+  </mujoco>
+  )";
+  mjModel* model = LoadModelFromString(xml, 0, 0);
+  ASSERT_THAT(model, testing::NotNull());
+  mj_deleteModel(model);
+}
+
 // ------------- test inertia -------------------------------------------------
 
 TEST_F(MjCMeshTest, SmallInertiaLoads) {