Remove cloth and rope composites and deprecate loop.

PiperOrigin-RevId: 568168329
Change-Id: Ida4a5236bef74828c7bf59affdc28adea3db53b1

doc/changelog.rst

@@ -84,35 +84,39 @@ General
          :ref:`conaffinity<body-geom-conaffinity>` attributes in the model and then setting them globally to ``0`` using
          |br| ``<default> <geom contype="0" conaffinity="0"/> </default>``.
 
-11. Added a new :ref:`dyntype<actuator-general-dyntype>`, ``filterexact``, which updates first-order filter states with
+   11. Removed the :at:`rope` and :at:`cloth` composite objects.
+
+       **Migration:** Users should use the :at:`cable` and :at:`shell` elasticity plugins.
+
+12. Added a new :ref:`dyntype<actuator-general-dyntype>`, ``filterexact``, which updates first-order filter states with
     the exact formula rather than with Euler integration.
-12. Added an actuator attribute, :ref:`actearly<actuator-general-actearly>`, which uses semi-implicit integration for
+13. Added an actuator attribute, :ref:`actearly<actuator-general-actearly>`, which uses semi-implicit integration for
     actuator forces: using the next step's actuator state to compute the current actuator forces at the current timestep.
-13. Renamed ``actuatorforcerange`` and ``actuatorforcelimited``, introduced in the previous version to
+14. Renamed ``actuatorforcerange`` and ``actuatorforcelimited``, introduced in the previous version to
     :ref:`actuatorfrcrange<body-joint-actuatorfrcrange>` and
     :ref:`actuatorfrclimited<body-joint-actuatorfrclimited>`, respectively.
-14. Added the flag :ref:`eulerdamp<option-flag-eulerdamp>`, which disables implicit integration of joint damping in the
+15. Added the flag :ref:`eulerdamp<option-flag-eulerdamp>`, which disables implicit integration of joint damping in the
     Euler integrator. See the :ref:`Numerical Integration<geIntegration>` section for more details.
-15. Added the flag :ref:`invdiscrete<option-flag-invdiscrete>`, which enables discrete-time inverse dynamics for all
+16. Added the flag :ref:`invdiscrete<option-flag-invdiscrete>`, which enables discrete-time inverse dynamics for all
     :ref:`integrators<option-integrator>` other than ``RK4``. See the flag documentation for more details.
-16. Added :ref:`ls_iterations<option-ls_iterations>` and :ref:`ls_tolerance<option-ls_tolerance>` options for adjusting
+17. Added :ref:`ls_iterations<option-ls_iterations>` and :ref:`ls_tolerance<option-ls_tolerance>` options for adjusting
     linesearch stopping criteria in CG and Newton solvers. These can be useful for performance tuning.
-17. Added ``mesh_pos`` and ``mesh_quat`` fields to :ref:`mjModel` to store the normalizing transformation applied to
+18. Added ``mesh_pos`` and ``mesh_quat`` fields to :ref:`mjModel` to store the normalizing transformation applied to
     mesh assets. Fixes `#409 <https://github.com/google-deepmind/mujoco/issues/409>`__ .
-18. Added camera :ref:`resolution<body-camera-resolution>` attribute and :ref:`camprojection<sensor-camprojection>`
+19. Added camera :ref:`resolution<body-camera-resolution>` attribute and :ref:`camprojection<sensor-camprojection>`
     sensor. If camera resolution is set to positive values, the camera projection sensor will report the location of a
     target site, projected onto the camera image, in pixel coordinates.
 
 Python bindings
 ^^^^^^^^^^^^^^^
 
-19. Fixed `#870 <https://github.com/google-deepmind/mujoco/issues/870>`__ where calling ``update_scene`` with an invalid
+20. Fixed `#870 <https://github.com/google-deepmind/mujoco/issues/870>`__ where calling ``update_scene`` with an invalid
     camera name used the default camera.
 
 Bug fixes
 ^^^^^^^^^
 
-20. Fixed a bug that was causing :ref:`geom margin<body-geom-margin>` to be ignored during the construction of
+21. Fixed a bug that was causing :ref:`geom margin<body-geom-margin>` to be ignored during the construction of
     midphase collision trees.
 
 

model/composite/cloth.xml

@@ -1,35 +0,0 @@
-<!-- Copyright 2021 DeepMind Technologies Limited
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-         http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
-<mujoco model="Cloth">
-  <include file="scene.xml"/>
-
-  <option timestep="0.002" solver="CG" tolerance="1e-6"/>
-
-  <size memory="10M"/>
-
-  <worldbody>
-
-    <body name="B3_5" pos="0 0 1">
-      <freejoint/>
-      <composite type="cloth" count="9 9 1" spacing="0.05" flatinertia="0.01">
-        <joint kind="main" damping="0.001"/>
-        <skin material="matcarpet" texcoord="true" inflate="0.005" subgrid="2"/>
-        <geom type="capsule" size="0.015 0.01" rgba=".8 .2 .1 1"/>
-      </composite>
-    </body>
-
-  </worldbody>
-</mujoco>

model/composite/loop.xml

@@ -1,32 +0,0 @@
-<!-- Copyright 2021 DeepMind Technologies Limited
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-         http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
-<mujoco model="Loop">
-  <include file="scene.xml"/>
-
-  <option timestep="0.002" jacobian="dense"/>
-
-  <size memory="2M"/>
-
-  <worldbody>
-    <body name="B0" pos="0 0 1">
-      <freejoint/>
-      <composite type="loop" count="20 1 1" spacing="0.04" offset="0 0 2">
-        <joint kind="main" damping="0.005"/>
-        <geom type="capsule" size=".01 .015" rgba=".8 .2 .1 1"/>
-      </composite>
-    </body>
-  </worldbody>
-</mujoco>

model/plugin/elasticity/flag.xml

@@ -23,22 +23,33 @@
 -->
   <statistic center=".4 0 .8" extent="1.3"/>
 
-  <option wind="5 5 0" density="10">
+  <option wind="5 5 0" density="10" solver="CG" tolerance="1e-6">
-    <flag constraint="disable"/>
   </option>
 
+  <extension>
+    <plugin plugin="mujoco.elasticity.shell"/>
+  </extension>
+
   <worldbody>
     <geom name="floor" type="plane" size="0 0 .1"/>
     <light diffuse=".6 .6 .6" specular="0.2 0.2 0.2" pos="0 0 4" dir="0 0 -1"/>
-    <body name="B0_0" pos="0 0 1">
+    <body pos="0 0 1">
-      <composite type="cloth" count="9 19 1" spacing="0.05" flatinertia="0.01">
+      <composite type="particle" count="9 19 1" spacing="0.05" flatinertia="0.01">
-        <joint kind="main" damping="0.001" stiffness=".1"/>
         <skin texcoord="true" inflate="0.005" subgrid="4"/>
-        <geom type="ellipsoid" size="0.025 0.01 0.025" rgba=".8 .2 .1 1"/>
+        <geom type="ellipsoid" size="0.025 0.01 0.025" rgba=".8 .2 .1 1" group="4"/>
-        <tendon kind="main" stiffness="100" damping=".001"/>
+        <plugin plugin="mujoco.elasticity.shell">
-        <tendon kind="shear" stiffness="100" damping=".001"/>
+          <config key="poisson" value="0"/>
+          <config key="damping" value="0.001"/>
+          <config key="thickness" value="1e-2"/>
+          <!--Units are in Pa (SI)-->
+          <config key="young" value="3e6"/>
+        </plugin>
       </composite>
     </body>
   </worldbody>
+
+  <equality>
+    <connect body1="B0_0_0" anchor="0 0 0" solref="0.0002 1"/>
+  </equality>
 </mujoco>
 

model/plugin/elasticity/plate.xml

@@ -41,7 +41,7 @@
     <composite type="particle" count="16 16 1" spacing="0.05" offset="0 0 1">
       <geom size=".02" rgba=".8 .2 .1 1" group="4" density="1000"
             condim="3" solref="0.01 1" solimp=".95 .99 .0001"/>
-      <skin inflate="0.01" rgba=".4 0 .3 1" subgrid="4"/>
+      <skin inflate="0.0001" rgba=".4 0 .3 1" subgrid="1"/>
       <plugin plugin="mujoco.elasticity.shell">
         <config key="poisson" value="0"/>
         <config key="damping" value="0.001"/>

src/user/user_composite.cc

@@ -293,16 +293,25 @@ bool mjCComposite::Make(mjCModel* model, mjCBody* body, char* error, int error_s
     return MakeGrid(model, body, error, error_sz);
 
   case mjCOMPTYPE_ROPE:
-    mju_warning("The \"rope\" composite type is deprecated. Please use \"cable\" instead.");
+    return comperr(error,
-    [[fallthrough]];
+                "The \"rope\" composite type is deprecated. Please use "
+                "\"cable\" instead.",
+                error_sz);
+
   case mjCOMPTYPE_LOOP:
+    mju_warning(
+        "The \"loop\" composite type is deprecated. Please use \"cable\" "
+        "instead.");
     return MakeRope(model, body, error, error_sz);
 
   case mjCOMPTYPE_CABLE:
     return MakeCable(model, body, error, error_sz);
 
   case mjCOMPTYPE_CLOTH:
-    return MakeCloth(model, body, error, error_sz);
+    return comperr(error,
+                   "The \"cloth\" composite type is deprecated. Please use "
+                   "\"shell\" instead.",
+                   error_sz);
 
   case mjCOMPTYPE_BOX:
   case mjCOMPTYPE_CYLINDER:
@@ -531,10 +540,18 @@ bool mjCComposite::MakeParticle(mjCModel* model, mjCBody* body, char* error, int
     }
   }
 
-  if (skin) {
+  if (skin && dim==3) {
     MakeSkin3(model);
   }
 
+  if (skin && dim==2) {
+    if (skinsubgrid>0) {
+      MakeSkin2Subgrid(model, skininflate);
+    } else {
+      MakeSkin2(model, skininflate);
+    }
+  }
+
   return true;
 }
 
@@ -1019,273 +1036,6 @@ mjCBody* mjCComposite::AddRopeBody(mjCModel* model, mjCBody* body, int ix, int i
 
 
 
-// make 2d cloth
-bool mjCComposite::MakeCloth(mjCModel* model, mjCBody* body, char* error, int error_sz) {
-  // check dim
-  if (dim!=2) {
-    return comperr(error, "Cloth must be two-dimensional", error_sz);
-  }
-
-  // check root body name prefix
-  char txt[200];
-  mju::sprintf_arr(txt, "%sB", prefix.c_str());
-  if (std::strncmp(txt, body->name.substr(0, strlen(txt)).c_str(), mju::sizeof_arr(txt))) {
-    mju::strcat_arr(txt, " must be the beginning of root body name");
-    return comperr(error, txt, error_sz);
-  }
-
-  // read origin coordinate from root body
-  mju::strcpy_arr(txt, body->name.substr(strlen(txt)).c_str());
-  int ox = -1, oy = -1;
-  char c;
-  if (sscanf(txt, "%d%c%d", &ox, &c, &oy)!=3 || c!='_') {
-    return comperr(error, "Root body name must contain X_Y coordinates", error_sz);
-  }
-  if (ox<0 || ox>=count[0] || oy<0 || oy>=count[1]) {
-    return comperr(error, "Root body coordinates out of range", error_sz);
-  }
-
-  // add origin
-  AddClothBody(model, body, ox, oy, ox, oy);
-
-  // add row: both directions
-  for (int i=-2; i<=2; i+=2) {
-    // init at origin
-    int ix = ox;
-
-    // process row to end
-    mjCBody* pbodyx = body;
-    while (1) {
-      // candidate neighbor
-      int ix1 = ix;
-      if (i==0) {
-        ix1 = mjMIN(count[0]-1, ix+1);
-      } else if (i==2) {
-        ix1 = mjMAX(0, ix-1);
-      }
-
-      // regular column
-      if (i!=-2) {
-        // stop if same
-        if (ix1==ix) {
-          break;
-        }
-
-        // add body, assign counter
-        pbodyx = AddClothBody(model, pbodyx, ix, oy, ix1, oy);
-        ix = ix1;
-      }
-
-      // add column: regular or center
-      for (int j=1; j<=3; j+=2) {
-        // init at row
-        int iy = oy;
-
-        // process column to end
-        mjCBody* pbodyy = pbodyx;
-        while (1) {
-          // candidate neighbor
-          int iy1;
-          if (j==1) {
-            iy1 = mjMIN(count[1]-1, iy+1);
-          } else {
-            iy1 = mjMAX(0, iy-1);
-          }
-
-          // stop if same
-          if (iy1==iy) {
-            break;
-          }
-
-          // add body, assign counter
-          pbodyy = AddClothBody(model, pbodyy, ix, iy, ix, iy1);
-          iy = iy1;
-        }
-      }
-
-      // center column added
-      if (i==-2) {
-        break;
-      }
-    }
-  }
-
-  // add main tendons
-  for (int iy=0; iy<count[1]; iy++) {
-    if (iy!=oy) {
-      for (int ix=0; ix<count[0]-1; ix++) {
-        char txt1[100], txt2[100];
-
-        // recover site names
-        mju::sprintf_arr(txt1, "%sS%d_%d", prefix.c_str(), ix, iy);
-        mju::sprintf_arr(txt2, "%sS%d_%d", prefix.c_str(), ix+1, iy);
-
-        // create tendon
-        mjCTendon* ten = model->AddTendon(def + mjCOMPKIND_TENDON);
-        ten->def = model->defaults[0];
-        mju::sprintf_arr(txt, "%sT%d_%d", prefix.c_str(), ix, iy);
-        ten->name = txt;
-        ten->WrapSite(txt1);
-        ten->WrapSite(txt2);
-
-        // add equality constraint
-        mjCEquality* eq = model->AddEquality(def + mjCOMPKIND_TENDON);
-        eq->def = model->defaults[0];
-        eq->type = mjEQ_TENDON;
-        eq->name1 = ten->name;
-      }
-    }
-  }
-
-  // shear for 2D
-  if (add[mjCOMPKIND_SHEAR]) {
-    MakeShear(model);
-  }
-
-  // skin
-  if (skin) {
-    if (skinsubgrid>0) {
-      MakeSkin2Subgrid(model, skininflate);
-    } else {
-      MakeSkin2(model, skininflate);
-    }
-  }
-
-  return true;
-}
-
-
-
-// add child body for cloth
-mjCBody* mjCComposite::AddClothBody(mjCModel* model, mjCBody* body,
-                                    int ix, int iy, int ix1, int iy1) {
-  char txt[100];
-  bool isroot = (ix==ix1 && iy==iy1);
-  double dx = spacing*(ix1-ix);
-  double dy = spacing*(iy1-iy);
-
-  // add child if not root
-  if (!isroot) {
-    body = body->AddBody();
-    mju::sprintf_arr(txt, "%sB%d_%d", prefix.c_str(), ix1, iy1);
-    body->name = txt;
-    mjuu_setvec(body->pos, dx, dy, 0);
-  }
-
-  // add geom, alternating rotations
-  mjCGeom* geom = body->AddGeom(def);
-  geom->def = body->def;
-  mju::sprintf_arr(txt, "%sG%d_%d", prefix.c_str(), ix1, iy1);
-  geom->name = txt;
-  mjuu_setvec(geom->pos, 0, 0, 0);
-  if ((ix1+iy1)%2) {
-    mjuu_setvec(geom->quat, sqrt(0.5), sqrt(0.5), 0, 0);
-  } else {
-    mjuu_setvec(geom->quat, 0.5, 0.5, 0.5, 0.5);
-  }
-
-  // make inertia flat
-  if (flatinertia>0) {
-    // set body mass = geom mass
-    body->mass = mjuu_defined(geom->_mass) ? geom->_mass :
-                 geom->density * geom->GetVolume();
-
-    // set body i-frame
-    mjuu_setvec(body->ipos, 0, 0, 0);
-    mjuu_setvec(body->iquat, 1, 0, 0, 0);
-
-    // desired equivalent inertia box
-    double size[3] = {0.5*spacing, 0.5*spacing, 0.5*spacing*flatinertia};
-
-    // convert to inertia
-    body->inertia[0] = body->mass*(size[1]*size[1]+size[2]*size[2])/3;
-    body->inertia[1] = body->mass*(size[0]*size[0]+size[2]*size[2])/3;
-    body->inertia[2] = body->mass*(size[0]*size[0]+size[1]*size[1])/3;
-
-    body->MakeInertialExplicit();
-  }
-
-  // add site
-  mjCSite* site = body->AddSite(def);
-  site->def = body->def;
-  site->type = mjGEOM_SPHERE;
-  mju::sprintf_arr(txt, "%sS%d_%d", prefix.c_str(), ix1, iy1);
-  site->name = txt;
-  mjuu_setvec(site->pos, 0, 0, 0);
-  mjuu_setvec(site->quat, 1, 0, 0, 0);
-
-  // root: no joints
-  if (isroot) {
-    return body;
-  }
-
-  // add main joint
-  for (int i=0; i<2; i++) {
-    // add joint
-    mjCJoint* jnt = body->AddJoint(&defjoint[mjCOMPKIND_JOINT][0]);
-    jnt->def = body->def;
-    mju::sprintf_arr(txt, "%sJ%d_%d_%d", prefix.c_str(), i, ix1, iy1);
-    jnt->name = txt;
-    jnt->type = mjJNT_HINGE;
-    mjuu_setvec(jnt->pos, -dx, -dy, 0);
-
-    // set universal axis depending on parent direction
-    mjuu_setvec(jnt->axis, 0, 0, 0);
-    if (ix!=ix1) {
-      jnt->axis[i+1] = 1;
-    } else {
-      jnt->axis[2*i] = 1;
-    }
-  }
-
-  // add twist joint
-  if (add[mjCOMPKIND_TWIST]) {
-    mjCJoint* jnt = body->AddJoint(&defjoint[mjCOMPKIND_TWIST][0]);
-    jnt->def = body->def;
-    mju::sprintf_arr(txt, "%sJT%d_%d", prefix.c_str(), ix1, iy1);
-    jnt->name = txt;
-    jnt->type = mjJNT_HINGE;
-    mjuu_setvec(jnt->pos, -dx, -dy, 0);
-    if (ix!=ix1) {
-      mjuu_setvec(jnt->axis, 1, 0, 0);
-    } else {
-      mjuu_setvec(jnt->axis, 0, 1, 0);
-    }
-
-    // add constraint
-    mjCEquality* eq = model->AddEquality(def + mjCOMPKIND_TWIST);
-    eq->def = model->defaults[0];
-    eq->type = mjEQ_JOINT;
-    eq->name1 = jnt->name;
-  }
-
-  // add stretch joint
-  if (add[mjCOMPKIND_STRETCH]) {
-    // add joint
-    mjCJoint* jnt = body->AddJoint(&defjoint[mjCOMPKIND_STRETCH][0]);
-    jnt->def = body->def;
-    mju::sprintf_arr(txt, "%sJS%d_%d", prefix.c_str(), ix1, iy1);
-    jnt->name = txt;
-    jnt->type = mjJNT_SLIDE;
-    mjuu_setvec(jnt->pos, -dx, -dy, 0);
-    if (ix!=ix1) {
-      mjuu_setvec(jnt->axis, 1, 0, 0);
-    } else {
-      mjuu_setvec(jnt->axis, 0, 1, 0);
-    }
-
-    // add constraint
-    mjCEquality* eq = model->AddEquality(def + mjCOMPKIND_STRETCH);
-    eq->def = model->defaults[0];
-    eq->type = mjEQ_JOINT;
-    eq->name1 = jnt->name;
-  }
-
-  return body;
-}
-
-
-
 // project from box to other shape
 void mjCComposite::BoxProject(double* pos) {
   // determine sizes
@@ -1490,6 +1240,46 @@ void mjCComposite::MakeSkin2(mjCModel* model, mjtNum inflate) {
   skin->inflate = inflate;
   skin->group = skingroup;
 
+  // copy skin from existing mesh
+  if (type==mjCOMPTYPE_PARTICLE && username.empty()) {
+    std::vector<int> face;
+    mjXUtil::String2Vector(userface, face);
+    int nvert = uservert.size()/3;
+
+    for (int j=0; j<2; j++) {
+      for (int i=0; i<nvert; i++) {
+        skin->vert.push_back(0);
+        skin->vert.push_back(0);
+        skin->vert.push_back(0);
+
+        mju::sprintf_arr(txt, "%sB%d", prefix.c_str(), i);
+        skin->bodyname.push_back(txt);
+        skin->bindpos.push_back(0);
+        skin->bindpos.push_back(0);
+        skin->bindpos.push_back(0);
+        skin->bindquat.push_back(1);
+        skin->bindquat.push_back(0);
+        skin->bindquat.push_back(0);
+        skin->bindquat.push_back(0);
+
+        vector<int> vertid;
+        vector<float> vertweight;
+        vertid.push_back(j*nvert+i);
+        vertweight.push_back(1);
+        skin->vertid.push_back(vertid);
+        skin->vertweight.push_back(vertweight);
+      }
+
+      for (int i=0; i<face.size()/3; i++) {
+        skin->face.push_back(j*nvert+face[3*i]-1);
+        skin->face.push_back(j*nvert+face[3*i+(j==0 ? 1 : 2)]-1);
+        skin->face.push_back(j*nvert+face[3*i+(j==0 ? 2 : 1)]-1);
+      }
+    }
+
+    return;
+  }
+
   // populate mesh: two sides
   for (int i=0; i<2; i++) {
     for (int ix=0; ix<count[0]; ix++) {
@@ -1564,7 +1354,7 @@ void mjCComposite::MakeSkin2(mjCModel* model, mjtNum inflate) {
   }
 
   // couple with bones
-  if (type==mjCOMPTYPE_CLOTH || type==mjCOMPTYPE_GRID) {
+  if (type==mjCOMPTYPE_PARTICLE || type==mjCOMPTYPE_GRID) {
     MakeClothBones(model, skin);
   } else if (type==mjCOMPTYPE_CABLE) {
     MakeCableBones(model, skin);
@@ -1582,7 +1372,11 @@ void mjCComposite::MakeClothBones(mjCModel* model, mjCSkin* skin) {
   for (int ix=0; ix<count[0]; ix++) {
     for (int iy=0; iy<count[1]; iy++) {
       // body name
-      mju::sprintf_arr(txt, "%sB%d_%d", prefix.c_str(), ix, iy);
+      if (type==mjCOMPTYPE_GRID) {
+        mju::sprintf_arr(txt, "%sB%d_%d", prefix.c_str(), ix, iy);
+      } else {
+        mju::sprintf_arr(txt, "%sB%d_%d_0", prefix.c_str(), ix, iy);
+      }
 
       // bind pose
       skin->bodyname.push_back(txt);
@@ -1616,7 +1410,11 @@ void mjCComposite::MakeClothBonesSubgrid(mjCModel* model, mjCSkin* skin) {
   for (int ix=0; ix<count[0]; ix++) {
     for (int iy=0; iy<count[1]; iy++) {
       // body name
-      mju::sprintf_arr(txt, "%sB%d_%d", prefix.c_str(), ix, iy);
+      if (type==mjCOMPTYPE_GRID) {
+        mju::sprintf_arr(txt, "%sB%d_%d", prefix.c_str(), ix, iy);
+      } else {
+        mju::sprintf_arr(txt, "%sB%d_%d_0", prefix.c_str(), ix, iy);
+      }
 
       // bind pose
       skin->bodyname.push_back(txt);
@@ -2121,7 +1919,7 @@ void mjCComposite::MakeSkin2Subgrid(mjCModel* model, mjtNum inflate) {
     skin->face.push_back(NN + iy+1 + (C0-1)*C1);
   }
 
-  if (type==mjCOMPTYPE_CLOTH || type==mjCOMPTYPE_GRID) {
+  if (type==mjCOMPTYPE_PARTICLE || type==mjCOMPTYPE_GRID) {
     MakeClothBonesSubgrid(model, skin);
   } else if (type==mjCOMPTYPE_CABLE) {
     MakeCableBonesSubgrid(model, skin);
@@ -2197,46 +1995,8 @@ void mjCComposite::MakeSkin3(mjCModel* model) {
   skin->inflate = skininflate;
   skin->group = skingroup;
 
-  // copy skin from existing mesh
-  if (type==mjCOMPTYPE_PARTICLE && username.empty()) {
-    std::vector<int> face;
-    mjXUtil::String2Vector(userface, face);
-    int nvert = uservert.size()/3;
-
-    for (int j=0; j<2; j++) {
-      for (int i=0; i<nvert; i++) {
-        skin->vert.push_back(0);
-        skin->vert.push_back(0);
-        skin->vert.push_back(0);
-
-        mju::sprintf_arr(txt, "%sB%d", prefix.c_str(), i);
-        skin->bodyname.push_back(txt);
-        skin->bindpos.push_back(0);
-        skin->bindpos.push_back(0);
-        skin->bindpos.push_back(0);
-        skin->bindquat.push_back(1);
-        skin->bindquat.push_back(0);
-        skin->bindquat.push_back(0);
-        skin->bindquat.push_back(0);
-
-        vector<int> vertid;
-        vector<float> vertweight;
-        vertid.push_back(j*nvert+i);
-        vertweight.push_back(1);
-        skin->vertid.push_back(vertid);
-        skin->vertweight.push_back(vertweight);
-      }
-
-      for (int i=0; i<face.size()/3; i++) {
-        skin->face.push_back(j*nvert+face[3*i]-1);
-        skin->face.push_back(j*nvert+face[3*i+(j==0 ? 1 : 2)]-1);
-        skin->face.push_back(j*nvert+face[3*i+(j==0 ? 2 : 1)]-1);
-      }
-    }
-  }
-
   // box
-  else if (type==mjCOMPTYPE_BOX || type==mjCOMPTYPE_PARTICLE) {
+  if (type==mjCOMPTYPE_BOX || type==mjCOMPTYPE_PARTICLE) {
     // z-faces
     MakeSkin3Box(skin, count[0], count[1], 1, vcnt, "%sB%d_%d_0");
     fmt = "%sB%d_%d_" + string(cnt2);

src/user/user_composite.h

@@ -74,7 +74,6 @@ class mjCComposite {
   bool MakeGrid(mjCModel* model, mjCBody* body, char* error, int error_sz);
   bool MakeRope(mjCModel* model, mjCBody* body, char* error, int error_sz);
   bool MakeCable(mjCModel* model, mjCBody* body, char* error, int error_sz);
-  bool MakeCloth(mjCModel* model, mjCBody* body, char* error, int error_sz);
   bool MakeBox(mjCModel* model, mjCBody* body, char* error, int error_sz);
   void MakeShear(mjCModel* model);
 
@@ -138,7 +137,6 @@ class mjCComposite {
 
  private:
   mjCBody* AddRopeBody(mjCModel* model, mjCBody* body, int ix, int ix1);
-  mjCBody* AddClothBody(mjCModel* model, mjCBody* body, int ix, int iy, int ix1, int iy1);
   mjCBody* AddCableBody(mjCModel* model, mjCBody* body, int ix, mjtNum normal[3], mjtNum prev_quat[4]);
 };
 

test/benchmark/engine_core_smooth_benchmark_test.cc

@@ -25,7 +25,7 @@ namespace mujoco {
 namespace {
 
 // number of steps to roll out before benhmarking
-static const int kNumWarmupSteps = 500;
+static const int kNumWarmupSteps = 200;
 
 // number of steps to benchmark
 static const int kNumBenchmarkSteps = 50;
@@ -102,7 +102,7 @@ void solveM_baseline(const mjModel* m, mjData* d, mjtNum* x, const mjtNum* y) {
 // ----------------------------- benchmark ------------------------------------
 
 static void BM_solveLD(benchmark::State& state, bool new_function) {
-  static mjModel* m = LoadModelFromPath("composite/cloth.xml");
+  static mjModel* m = LoadModelFromPath("plugin/elasticity/coil.xml");
   mjData* d = mj_makeData(m);
 
   // warm-up rollout to get a typical state

test/benchmark/engine_util_sparse_benchmark_test.cc

@@ -348,7 +348,7 @@ void ABSL_ATTRIBUTE_NOINLINE mulMatVecSparse_8(mjtNum* res,
 // ----------------------------- benchmark ------------------------------------
 
 static void BM_MatVecSparse(benchmark::State& state, int unroll) {
-  static mjModel* m = LoadModelFromPath("composite/cloth.xml");
+  static mjModel* m = LoadModelFromPath("plugin/elasticity/flag.xml");
   mjData* d = mj_makeData(m);
 
   // warm-up rollout to get a typical state

test/benchmark/parse_benchmark_test.cc

@@ -48,13 +48,14 @@ static void run_parse_benchmark(const std::string xml_path, benchmark::State& st
 // separately in CPU profiles (and don't get replaced with raw calls to
 // run_parse_benchmark).
 
-void ABSL_ATTRIBUTE_NO_TAIL_CALL BM_ParseCloth(benchmark::State& state) {
+void ABSL_ATTRIBUTE_NO_TAIL_CALL BM_ParseCable(benchmark::State& state) {
-  run_parse_benchmark(GetModelPath("composite/cloth.xml"), state);
+  run_parse_benchmark(GetModelPath("plugin/elasticity/flag.xml"), state);
 }
-BENCHMARK(BM_ParseCloth);
+BENCHMARK(BM_ParseCable);
 
 void ABSL_ATTRIBUTE_NO_TAIL_CALL BM_ParseFlag(benchmark::State& state) {
-  run_parse_benchmark(GetModelPath("flag/flag.xml"), state);
+  run_parse_benchmark(GetModelPath("../test/benchmark/testdata/flag.xml"),
+                      state);
 }
 BENCHMARK(BM_ParseFlag);
 

test/benchmark/step_benchmark_test.cc

@@ -79,12 +79,12 @@ static void run_step_benchmark(const mjModel* model, benchmark::State& state) {
 // separately in CPU profiles (and don't get replaced with raw calls to
 // run_step_benchmark).
 
-void ABSL_ATTRIBUTE_NO_TAIL_CALL BM_StepCloth(benchmark::State& state) {
+void ABSL_ATTRIBUTE_NO_TAIL_CALL BM_StepCable(benchmark::State& state) {
   MujocoErrorTestGuard guard;
-  static mjModel* model = LoadModelFromPath("composite/cloth.xml");
+  static mjModel* model = LoadModelFromPath("plugin/elasticity/flag.xml");
   run_step_benchmark(model, state);
 }
-BENCHMARK(BM_StepCloth);
+BENCHMARK(BM_StepCable);
 
 void ABSL_ATTRIBUTE_NO_TAIL_CALL BM_StepParticle(benchmark::State& state) {
   MujocoErrorTestGuard guard;
@@ -95,7 +95,8 @@ BENCHMARK(BM_StepParticle);
 
 void ABSL_ATTRIBUTE_NO_TAIL_CALL BM_StepFlag(benchmark::State& state) {
   MujocoErrorTestGuard guard;
-  static mjModel* model = LoadModelFromPath("flag/flag.xml");
+  static mjModel* model =
+      LoadModelFromPath("../test/benchmark/testdata/flag.xml");
   run_step_benchmark(model, state);
 }
 BENCHMARK(BM_StepFlag);

test/user/user_composite_test.cc

@@ -57,34 +57,6 @@ TEST_F(UserCompositeTest, MultipleJointsNotAllowedUnlessParticle) {
               HasSubstr("Only particles are allowed to have multiple joints"));
 }
 
-TEST_F(UserCompositeTest, StretchAndTwistAllowed) {
-  static constexpr char xml[] = R"(
-  <mujoco>
-  <worldbody>
-    <body name="B10">
-      <freejoint/>
-      <composite type="rope" count="21 1 1" spacing="0.04">
-        <joint kind="main" damping="0.005"/>
-        <joint kind="stretch" damping="0.005"/>
-        <joint kind="twist" damping="0.005"/>
-        <geom type="capsule" size=".01 .015"/>
-      </composite>
-    </body>
-  </worldbody>
-  </mujoco>
-  )";
-  static char warning[1024];
-  warning[0] = '\0';
-  mju_user_warning = [](const char* msg) {
-    util::strcpy_arr(warning, msg);
-  };
-  std::array<char, 1024> error;
-  mjModel* m = LoadModelFromString(xml, error.data(), error.size());
-  EXPECT_THAT(m, NotNull());
-  EXPECT_THAT(warning, HasSubstr("deprecated"));
-  mj_deleteModel(m);
-}
-
 TEST_F(UserCompositeTest, SpacingGreaterThanGeometry) {
   static constexpr char xml[] = R"(
   <mujoco>

test/xml/xml_native_writer_test.cc

@@ -795,12 +795,10 @@ TEST_F(XMLWriterTest, WritesSkin) {
   static constexpr char xml[] = R"(
   <mujoco>
     <worldbody>
-      <body name="B0_0" pos="0 0 0">
+      <composite type="grid" count="2 2 1" spacing="0.05">
-        <composite type="cloth" count="2 2 1" spacing="0.05">
+        <skin texcoord="true"/>
-          <skin texcoord="true"/>
+        <geom size=".01"/>
-          <geom type="ellipsoid" size="1 1 1"/>
+      </composite>
-        </composite>
-      </body>
     </worldbody>
   </mujoco>
   )";
@@ -1085,7 +1083,8 @@ TEST_F(PluginTest, WriteReadCompare) {
 
         if (!mtemp) {
           // if failing because assets are missing, accept the test
-          ASSERT_THAT(error.data(), HasSubstr("file")) << error.data();
+          ASSERT_THAT(error.data(), HasSubstr("file"))
+              << error.data() << " from " << xml.c_str();
         } else {
           // for a particularly difficult example, relax the tolerance
           mjtNum tol =