Elliptic friction in MJX.

PiperOrigin-RevId: 641384367
Change-Id: I510c565940324fbbf392ce537ce27e0cb9af3eb1

mjx/mujoco/mjx/test_data/constraints.xml

@@ -58,7 +58,7 @@
       <geom class="box" condim="4"/>
     </body>
 
-    <body name="box_condim6" pos="6 0 0">
+    <body name="box_condim6" pos="7 0 0">
       <freejoint/>
       <geom class="box" condim="6"/>
     </body>
@@ -75,4 +75,13 @@
     <motor gear="50000" joint="joint3" name="act2"/>
     <motor gear="75000" joint="joint4" name="act3"/>
   </actuator>
+
+  <keyframe>
+    <!-- keyframe 0: default position with some motion, zero contacts -->
+    <key qpos='1 0 0 0 -1 0 0 1 0 0 0 0 0 1 0 0 0 4 0 0 1 0 0 0 5 0 0 1 0 0 0 6 0 0 1 0 0 0 7 0 0 1 0 0 0' qvel='1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1'/>
+    <!-- keyframe 1: some contacts but constraints are quadratic -->
+    <key qpos='1 0.0011 -8.2e-07 -0.0011 -0.82 1.9 -0.58 0.97 -0.14 0.17 -0.069 0.22 0.29 0.93 0.2 0.15 0.28 4.3 0.23 -0.26 0.97 0.12 0.11 0.18 5.4 0.25 -0.26 0.97 0.11 0.16 0.17 6.4 0.25 -0.26 0.97 0.11 0.16 0.17 7.4 0.25 -0.26 0.97 0.11 0.16 0.17' qvel='-0.14 3.3e-05 0.14 -0.14 -0.93 -3.6 -1.8 1 -0.57 -0.16 0.21 1.1 1 2.2 0.65 1.3 -4.2 -2.6 -5.6 0.54 1.6 2.8 -3.7 -2.3 0.7 -1.8 1.6 2.8 -3.7 -2.3 0.62 -1.8 1.6 2.8 -3.7 -2.3 0.61 -1.8'/>
+    <!-- keyframe 2: some contacts and some constraints are in cone state (for elliptic) -->
+    <key qpos='1 0.0087 2.4e-07 -0.0086 -0.89 1.8 -0.77 0.98 -0.2 -0.0022 -0.026 0.19 0.33 0.86 0.32 0.064 0.38 4.4 0.36 -0.81 0.97 -0.0013 -0.0011 0.25 5.6 0.52 -0.75 0.98 -0.018 0.17 0.094 6.6 0.52 -0.75 0.98 -0.017 0.16 0.094 7.6 0.52 -0.76 0.98 -0.017 0.16 0.094' qvel='0.2 -1.8e-05 -0.2 -0.72 0.072 0.025 0.015 -4.9 0.35 -0.22 0.26 0.99 -4.6 1.7 1.1 0.52 -0.73 0.16 7.9 1 0.043 -0.042 1.3 1.6 -1.6 0.98 0.027 -0.024 1.3 1.6 -1.8 0.96 0.025 -0.022 1.3 1.6 -1.8 0.96'/>
+  </keyframe>
 </mujoco>