Add touch sensor to MJX.

PiperOrigin-RevId: 688056696
Change-Id: I50b0ebf3141aab0a5b07e5ae770101ff8b7737d4

mjx/mujoco/mjx/test_data/sensor/sensor.xml

@@ -27,6 +27,7 @@
 -subtreelinvel
 -subtreeangmom
 * acceleration/force-dependent sensors:
+-touch
 -accelerometer
 -force
 -torque
@@ -100,6 +101,17 @@
       <site name="site_torque"/>
       <geom size="0.1"/>
     </body>
+
+    <!-- plane and body for touch sensors -->
+    <geom type="plane" size="1 1 .1" pos="-20 -20 -20"/>
+    <body pos="-20 -20 -19.985">
+      <joint type="slide" axis="0 0 1"/>
+      <joint type="hinge" axis="0 1 0"/>
+      <geom type="capsule" fromto="-.5 0 0 .5 0 0" size="0.0125"/>
+      <site name="touch_sphere" type="sphere" pos="-0.5 0 0" size="0.025"/>
+      <site name="touch_capsule" type="capsule" fromto="-0.1 0 0.01 0.1 0 0.01" size="0.025"/>
+      <site name="touch_box" pos="0.5 0 0" type="box" size="0.025 0.025 0.025"/>
+    </body>
   </worldbody>
 
   <actuator>
@@ -121,6 +133,7 @@
   </tendon>
 
   <sensor>
+    <touch name="touch_sphere" site="touch_sphere"/>
     <torque site="site_torque"/>
     <tendonpos tendon="fixed"/>
     <tendonvel tendon="fixed"/>
@@ -128,6 +141,7 @@
     <velocimeter name="velocimeter0" site="site0"/>
     <velocimeter name="velocimeter0cutoff" site="site0" cutoff="3e-4"/>
     <gyro name="gyro0" site="site0"/>
+    <touch name="touch_box" site="touch_box"/>
     <gyro name="gyro0cutoff" site="site0" cutoff="2e-3"/>
     <rangefinder name="rangefinder0" site="site_rangefinder0"/>
     <accelerometer name="accelerometer1" site="site1"/>
@@ -138,6 +152,7 @@
     <jointpos name="jointpos0cutoff" joint="hinge0" cutoff="1e-4"/>
     <jointvel name="jointvel0" joint="hinge0"/>
     <jointvel name="jointvel0cutoff" joint="hinge0" cutoff="1e-3"/>
+    <touch name="touch_capsule" site="touch_capsule"/>
     <actuatorfrc name="actuatorfrc0" actuator="motor0"/>
     <framelinvel name="framelinvel3" objtype="site" objname="site3"/>
     <framelinvel name="framelinvel3ref" objtype="site" objname="site3" reftype="body" refname="body2"/>