Add mjs_attachFrame to user_api.

PiperOrigin-RevId: 625648309
Change-Id: I4d6dfc4d38ad6ce688df83eb7cc2c34676076193

src/user/user_api.cc

@@ -91,6 +91,17 @@ int mjs_attachBody(mjsFrame* parent, const mjsBody* child,
 
 
 
+// attach frame to a parent body
+int mjs_attachFrame(mjsBody* parent, const mjsFrame* child,
+                    const char* prefix, const char* suffix) {
+  mjCBody* body_parent = static_cast<mjCBody*>(parent->element);
+  mjCFrame* child_frame = static_cast<mjCFrame*>(child->element);
+  *body_parent += std::string(prefix) + *child_frame + std::string(suffix);
+  return 0;
+}
+
+
+
 // get error message from model
 const char* mjs_getError(mjSpec* s) {
   mjCModel* modelC = static_cast<mjCModel*>(s->element);

src/user/user_api.h

@@ -750,6 +750,10 @@ MJAPI mjModel* mjs_compile(mjSpec* s, const mjVFS* vfs);
 MJAPI int mjs_attachBody(mjsFrame* parent, const mjsBody* child,
                          const char* prefix, const char* suffix);
 
+// Attach child frame to a parent body, return 0 if success
+MJAPI int mjs_attachFrame(mjsBody* parent, const mjsFrame* child,
+                          const char* prefix, const char* suffix);
+
 // Get error message from model.
 MJAPI const char* mjs_getError(mjSpec* s);
 

src/user/user_objects.cc

@@ -729,6 +729,49 @@ mjCBody& mjCBody::operator+=(const mjCBody& other) {
 
 
 
+// attach frame to body
+mjCBody& mjCBody::operator+=(const mjCFrame& other) {
+  mjCBody* subtree = other.body;
+  other.model->prefix = other.prefix;
+  other.model->suffix = other.suffix;
+
+  // map old frames to indices
+  std::map<mjCFrame*, int> fmap;
+  for (int i=0; i<subtree->frames.size(); i++) {
+    fmap[subtree->frames[i]] = i;
+  }
+
+  // copy children that are inside the input frame
+  CopyList(frames, subtree->frames, fmap, &other);  // needs to be done first
+  CopyList(geoms, subtree->geoms, fmap, &other);
+  CopyList(joints, subtree->joints, fmap, &other);
+  CopyList(sites, subtree->sites, fmap, &other);
+  CopyList(cameras, subtree->cameras, fmap, &other);
+  CopyList(lights, subtree->lights, fmap, &other);
+
+  for (int i=0; i<subtree->bodies.size(); i++) {
+    if (subtree->bodies[i]->frame != &other) {
+      continue;
+    }
+    bodies.push_back(new mjCBody(*subtree->bodies[i], model));  // triggers recursive call
+    bodies.back()->frame =
+        subtree->bodies[i]->frame ? frames[fmap[subtree->bodies[i]->frame]] : nullptr;
+  }
+
+  // name space
+  this->NameSpace(other.model);
+
+  // attach referencing elements
+  *model += *other.model;
+
+  // clear namespace and return body
+  other.model->prefix.clear();
+  other.model->suffix.clear();
+  return *this;
+}
+
+
+
 // copy src list of elements into dst; set body, model and frame
 template <typename T>
 void mjCBody::CopyList(std::vector<T*>& dst, const std::vector<T*>& src,

src/user/user_objects.h

@@ -275,6 +275,7 @@ class mjCBody : public mjCBody_, private mjsBody {
 
   // API for adding existing objects to body
   mjCBody& operator+=(const mjCBody& other);
+  mjCBody& operator+=(const mjCFrame& other);
 
   // API for accessing objects
   int NumObjects(mjtObj type);
@@ -360,7 +361,6 @@ class mjCFrame : public mjCFrame_, private mjsFrame {
   void SetParent(mjCBody* _body);
 
   mjCFrame& operator+=(const mjCBody& other);
-  mjCFrame& operator+=(const mjCFrame& other);
 
  private:
   mjCFrame(mjCModel* = 0, mjCFrame* = 0);      // constructor

test/user/user_api_test.cc

@@ -196,20 +196,18 @@ TEST_F(PluginTest, RecompileCompareCache) {
 }
 
 // -------------------------------- test attach -------------------------------
-TEST_F(MujocoTest, AttachSame) {
+static constexpr char xml_child[] = R"(
-  std::array<char, 1000> er;
-  mjtNum tol = 0;
-  std::string field = "";
-
-  static constexpr char xml[] = R"(
   <mujoco>
     <worldbody>
-      <body name="body">
+      <frame name="pframe">
-        <joint type="hinge" name="hinge"/>
+        <body name="body">
-        <geom type="cylinder" size=".1 1 0"/>
+          <joint type="hinge" name="hinge"/>
-        <light mode="targetbody" target="child"/>
+          <geom type="cylinder" size=".1 1 0"/>
-        <body name="child"/>
+          <light mode="targetbody" target="targetbody"/>
-      </body>
+          <body name="targetbody"/>
+          <body/>
+        </body>
+      </frame>
       <body name="ignore"/>
       <frame name="frame" pos=".1 0 0" euler="0 90 0"/>
     </worldbody>
@@ -227,26 +225,33 @@ TEST_F(MujocoTest, AttachSame) {
       <position name="fixed" tendon="fixed"/>
     </actuator>
     <contact>
-      <exclude body1="body" body2="child"/>
+      <exclude body1="body" body2="targetbody"/>
     </contact>
   </mujoco>)";
 
+TEST_F(MujocoTest, AttachSame) {
+  std::array<char, 1000> er;
+  mjtNum tol = 0;
+  std::string field = "";
+
   static constexpr char xml_result[] = R"(
   <mujoco>
     <worldbody>
       <body name="body">
         <joint type="hinge" name="hinge"/>
         <geom type="cylinder" size=".1 1 0"/>
-        <light mode="targetbody" target="child"/>
+        <light mode="targetbody" target="targetbody"/>
-        <body name="child"/>
+        <body name="targetbody"/>
+        <body/>
       </body>
       <body name="ignore"/>
       <frame name="frame" pos=".1 0 0" euler="0 90 0">
         <body name="attached-body-1">
           <joint type="hinge" name="attached-hinge-1"/>
           <geom type="cylinder" size=".1 1 0"/>
-          <light mode="targetbody" target="attached-child-1"/>
+          <light mode="targetbody" target="attached-targetbody-1"/>
-          <body name="attached-child-1"/>
+          <body name="attached-targetbody-1"/>
+          <body/>
         </body>
       </frame>
     </worldbody>
@@ -270,13 +275,13 @@ TEST_F(MujocoTest, AttachSame) {
       <position name="attached-fixed-1" tendon="attached-fixed-1"/>
     </actuator>
     <contact>
-      <exclude body1="body" body2="child"/>
+      <exclude body1="body" body2="targetbody"/>
-      <exclude body1="attached-body-1" body2="attached-child-1"/>
+      <exclude body1="attached-body-1" body2="attached-targetbody-1"/>
     </contact>
   </mujoco>)";
 
   // create parent
-  mjSpec* parent = ParseSpecFromString(xml, er.data(), er.size());
+  mjSpec* parent = ParseSpecFromString(xml_child, er.data(), er.size());
   EXPECT_THAT(parent, NotNull()) << er.data();
 
   // get frame
@@ -296,10 +301,10 @@ TEST_F(MujocoTest, AttachSame) {
   EXPECT_THAT(m_attached, NotNull());
 
   // check full name stored in mjModel
-  EXPECT_STREQ(mj_id2name(m_attached, mjOBJ_BODY, 4), "attached-body-1");
+  EXPECT_STREQ(mj_id2name(m_attached, mjOBJ_BODY, 5), "attached-body-1");
 
   // check body 3 is attached to the world
-  EXPECT_THAT(m_attached->body_parentid[3], 0);
+  EXPECT_THAT(m_attached->body_parentid[4], 0);
 
   // compare with expected XML
   mjModel* m_expected = LoadModelFromString(xml_result, er.data(), er.size());
@@ -330,32 +335,6 @@ TEST_F(MujocoTest, AttachDifferent) {
     </worldbody>
   </mujoco>)";
 
-  static constexpr char xml_child[] = R"(
-  <mujoco>
-    <worldbody>
-      <body name="body">
-        <joint type="hinge" name="hinge"/>
-        <geom type="cylinder" size=".1 1 0"/>
-          <body name="named"/>
-          <body/>
-      </body>
-      <body name="discard"/>
-    </worldbody>
-    <sensor>
-      <framepos name="keep" objtype="body" objname="body"/>
-      <framepos name="discard" objtype="body" objname="discard"/>
-    </sensor>
-    <tendon>
-      <fixed name="fixed">
-        <joint joint="hinge" coef="2"/>
-      </fixed>
-    </tendon>
-    <actuator>
-      <position joint="hinge"/>
-      <position tendon="fixed"/>
-    </actuator>
-  </mujoco>)";
-
   static constexpr char xml_result[] = R"(
   <mujoco>
     <worldbody>
@@ -366,14 +345,15 @@ TEST_F(MujocoTest, AttachDifferent) {
           <body name="attached-body-1">
             <joint type="hinge" name="attached-hinge-1"/>
             <geom type="cylinder" size=".1 1 0"/>
-              <body name="attached-named-1"/>
+            <light mode="targetbody" target="attached-targetbody-1"/>
+              <body name="attached-targetbody-1"/>
               <body/>
           </body>
         </frame>
       </body>
     </worldbody>
     <sensor>
-      <framepos name="attached-keep-1" objtype="body" objname="attached-body-1"/>
+      <framepos name="attached-sensor-1" objtype="body" objname="attached-body-1"/>
     </sensor>
     <tendon>
       <fixed name="attached-fixed-1">
@@ -381,9 +361,12 @@ TEST_F(MujocoTest, AttachDifferent) {
       </fixed>
     </tendon>
     <actuator>
-      <position joint="attached-hinge-1"/>
+      <position name="attached-hinge-1" joint="attached-hinge-1"/>
-      <position tendon="attached-fixed-1"/>
+      <position name="attached-fixed-1" tendon="attached-fixed-1"/>
     </actuator>
+    <contact>
+      <exclude body1="attached-body-1" body2="attached-targetbody-1"/>
+    </contact>
   </mujoco>)";
 
   // model with one free sphere and a frame
@@ -403,7 +386,7 @@ TEST_F(MujocoTest, AttachDifferent) {
   EXPECT_THAT(body, NotNull());
 
   // attach child to parent frame
-  EXPECT_THAT(
+  EXPECT_EQ(
       mjs_attachBody(frame, body, /*prefix=*/"attached-", /*suffix=*/"-1"), 0);
 
   // compile new model
@@ -430,5 +413,100 @@ TEST_F(MujocoTest, AttachDifferent) {
   mj_deleteModel(m_expected);
 }
 
+TEST_F(MujocoTest, AttachFrame) {
+  std::array<char, 1000> er;
+  mjtNum tol = 0;
+  std::string field = "";
+
+  static constexpr char xml_parent[] = R"(
+  <mujoco>
+    <worldbody>
+      <body name="sphere">
+        <freejoint/>
+        <geom size=".1"/>
+        <frame name="frame" pos=".1 0 0" euler="0 90 0"/>
+      </body>
+    </worldbody>
+  </mujoco>)";
+
+  static constexpr char xml_result[] = R"(
+  <mujoco>
+    <worldbody>
+      <body name="sphere">
+        <freejoint/>
+        <geom size=".1"/>
+        <frame name="frame" pos=".1 0 0" euler="0 90 0"/>
+        <frame name="pframe">
+          <body name="attached-body-1">
+            <joint type="hinge" name="attached-hinge-1"/>
+            <geom type="cylinder" size=".1 1 0"/>
+            <light mode="targetbody" target="attached-targetbody-1"/>
+              <body name="attached-targetbody-1"/>
+              <body/>
+          </body>
+        </frame>
+      </body>
+    </worldbody>
+    <sensor>
+      <framepos name="attached-sensor-1" objtype="body" objname="attached-body-1"/>
+    </sensor>
+    <tendon>
+      <fixed name="attached-fixed-1">
+        <joint joint="attached-hinge-1" coef="2"/>
+      </fixed>
+    </tendon>
+    <actuator>
+      <position name="attached-hinge-1" joint="attached-hinge-1"/>
+      <position name="attached-fixed-1" tendon="attached-fixed-1"/>
+    </actuator>
+    <contact>
+      <exclude body1="attached-body-1" body2="attached-targetbody-1"/>
+    </contact>
+  </mujoco>)";
+
+  // model with one free sphere and a frame
+  mjSpec* parent = ParseSpecFromString(xml_parent, er.data(), er.size());
+  EXPECT_THAT(parent, NotNull()) << er.data();
+
+  // get frame
+  mjsBody* body = mjs_findBody(parent, "sphere");
+  EXPECT_THAT(body, NotNull());
+
+  // model with one cylinder and a hinge
+  mjSpec* child = ParseSpecFromString(xml_child, er.data(), er.size());
+  EXPECT_THAT(child, NotNull()) << er.data();
+
+  // get subtree
+  mjsFrame* frame = mjs_findFrame(child, "pframe");
+  EXPECT_THAT(frame, NotNull());
+
+  // attach child to parent frame
+  EXPECT_THAT(
+      mjs_attachFrame(body, frame, /*prefix=*/"attached-", /*suffix=*/"-1"), 0);
+
+  // compile new model
+  mjModel* m_attached = mjs_compile(parent, 0);
+  EXPECT_THAT(m_attached, NotNull());
+
+  // check full name stored in mjModel
+  EXPECT_STREQ(mj_id2name(m_attached, mjOBJ_BODY, 2), "attached-body-1");
+
+  // check body 2 is attached to body 1
+  EXPECT_THAT(m_attached->body_parentid[2], 1);
+
+  // compare with expected XML
+  mjModel* m_expected = LoadModelFromString(xml_result, er.data(), er.size());
+  EXPECT_THAT(m_expected, NotNull()) << er.data();
+  EXPECT_LE(CompareModel(m_attached, m_expected, field), tol)
+            << "Expected and attached models are different!\n"
+            << "Different field: " << field << '\n';;
+
+  // destroy everything
+  mjs_deleteSpec(parent);
+  mjs_deleteSpec(child);
+  mj_deleteModel(m_attached);
+  mj_deleteModel(m_expected);
+}
+
 }  // namespace
 }  // namespace mujoco