Move flex damping to the engine and remove membrane and solid plugins.

PiperOrigin-RevId: 676434954
Change-Id: I24e8dbaa90afcffd613a9cf106ef8b7262195328

model/flex/floppy.xml

@@ -16,10 +16,6 @@
 <mujoco model="Floppy">
   <include file="scene.xml"/>
 
-  <extension>
-    <plugin plugin="mujoco.elasticity.solid"/>
-  </extension>
-
   <compiler autolimits="true"/>
 
   <option solver="CG" tolerance="1e-6" timestep=".001"/>
@@ -35,7 +31,6 @@
               radius=".0" rgba="0 .7 .7 1" name="softbody" dim="3" mass="25">
       <contact condim="3" solref="0.01 1" solimp=".95 .99 .0001" selfcollide="none"/>
       <elasticity young="5e4" damping="0.002" poisson="0.2"/>
-      <plugin plugin="mujoco.elasticity.solid"/>
     </flexcomp>
 
     <body>

model/flex/jelly.xml

@@ -16,10 +16,6 @@
 <mujoco model="Jelly">
   <include file="scene.xml"/>
 
-  <extension>
-    <plugin plugin="mujoco.elasticity.solid"/>
-  </extension>
-
   <option solver="CG" tolerance="1e-6" timestep=".001" integrator="implicitfast"/>
 
   <size memory="10M"/>
@@ -47,7 +43,6 @@
       <edge damping="1"/>
       <contact selfcollide="none"/>
       <elasticity young="5e4"/>
-      <plugin plugin="mujoco.elasticity.solid"/>
     </flexcomp>
   </worldbody>
 </mujoco>

model/flex/press.xml

@@ -16,10 +16,6 @@
 <mujoco model="Press">
   <include file="scene.xml"/>
 
-  <extension>
-    <plugin plugin="mujoco.elasticity.solid"/>
-  </extension>
-
   <compiler autolimits="true"/>
 
   <option solver="Newton" tolerance="1e-6" timestep=".001" integrator="implicitfast"/>
@@ -36,7 +32,6 @@
       <contact condim="3" solref="0.01 1" solimp=".95 .99 .0001" selfcollide="none"/>
       <edge damping="1"/>
       <elasticity young="1e4" poisson="0.4"/>
-      <plugin plugin="mujoco.elasticity.solid"/>
     </flexcomp>
 
     <flexcomp name="B" type="grid" count="4 4 4" spacing=".2 .2 .2" pos="1 0 .5"
@@ -44,7 +39,6 @@
       <contact condim="3" solref="0.01 1" solimp=".95 .99 .0001" selfcollide="none"/>
       <edge damping="1"/>
       <elasticity young="5e4" poisson="0"/>
-      <plugin plugin="mujoco.elasticity.solid"/>
     </flexcomp>
 
     <body>

model/flex/scene.xml

@@ -0,0 +1,41 @@
+<!-- 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>
+  <compiler meshdir="asset" texturedir="asset"/>
+
+  <statistic meansize=".05"/>
+
+  <visual>
+    <rgba haze="0.15 0.25 0.35 1"/>
+    <quality shadowsize="4096"/>
+    <map stiffness="700" shadowscale="0.5" fogstart="1" fogend="15" zfar="40" haze="1"/>
+  </visual>
+
+  <asset>
+    <texture type="skybox" builtin="gradient" rgb1="0.3 0.5 0.7" rgb2="0 0 0" width="512" height="512"/>
+    <texture name="texplane" type="2d" builtin="checker" rgb1=".2 .3 .4" rgb2=".1 0.15 0.2"
+      width="512" height="512" mark="cross" markrgb=".8 .8 .8"/>
+
+    <material name="matplane" reflectance="0.3" texture="texplane" texrepeat="10 10" texuniform="true"/>
+  </asset>
+
+  <worldbody>
+    <light diffuse=".4 .4 .4" specular="0.1 0.1 0.1" pos="0 0 2.0" dir="0 0 -1" castshadow="false"/>
+    <light directional="true" diffuse=".8 .8 .8" specular="0.2 0.2 0.2" pos="0 0 4" dir="0 0 -1"/>
+
+    <geom name="ground" type="plane" size="0 0 1" pos="0 0 0" quat="1 0 0 0" material="matplane" condim="1"/>
+  </worldbody>
+</mujoco>

model/flex/trampoline.xml

@@ -16,11 +16,6 @@
 <mujoco model="Trampoline">
   <include file="scene.xml"/>
 
-  <extension>
-    <plugin plugin="mujoco.elasticity.shell"/>
-    <plugin plugin="mujoco.elasticity.membrane"/>
-  </extension>
-
   <option timestep="0.001" solver="CG" tolerance="1e-6" integrator="implicitfast"/>
 
   <size memory="10M"/>
@@ -46,7 +41,6 @@
       <edge equality="false" damping="10"/>
       <elasticity young="3e5" poisson="0" thickness="1e-2"/>
       <pin id="0 15 240 255"/>
-      <plugin plugin="mujoco.elasticity.membrane"/>
     </flexcomp>
   </worldbody>
 </mujoco>