Unity Version

[troytully]

Intro

Hi!

I am a Post-doc in one of the original Haptix labs that a lot of MuJoCo was developed for (we have some very old mujoco code!!).

My setup

I downloaded this version of MuJoCo on 11/15/25. There is no version in the downloaded folder from git and the changelog inside the unity plugin only mentions 2.1.2 changes....

My question

I've been trying to get my older files to run in Unity 6. I had it compiling and running off webGL about a year ago in 2022.3 but the model wouldn't react to gravity, so I was guessing it had some sort of issue calling the mj code. After coming back to the project a year later, I thought I should update everything (mujoco dll and unity). After updating it won't build anymore and when I press play the unity editor just completely crashes and it can't even pause on an error. I then tried the 22 humanoids scene and that one also crashed but at least Unity was able to catch the error and it offered to send a crash report.

LukeHand.xml
Scene_Fragile_Block_TD.xml
22_humanoids.xml

Is there a proper version? Nothing in the doc that I found suggested that unity 6 wouldn't work but I want to check with the community.

Is there anything in my older XML files that wouldn't work with the newer MuJoCo or the Unity Plug-In?

Minimal model and/or code that explain my question

<default>
    <position ctrllimited="true" forcelimited="true" gear="57.29577951"/>
    <geom solimp="0.95 0.99 0.001" solref="0.01 1" friction="1.0 0.01 0.001"/>

    <default class="robot">
        <geom material="robot" contype="1" conaffinity="2" condim="4"/>
        <site rgba=".3 .9 .3 .3" type="box" group="3"/>
        <joint limited="true" pos="0 0 0" axis="1 0 0" range="0 90" damping="0.1" armature="0.002"/>

        <default class="RP">
            <joint damping="0.05" armature="0.001"/>
        </default>
    </default>

    <default class="couple">
        <equality solref="0.05 0.5" solimp="0.0001 0.0001 0"/>
    </default>    

    <default class="free">
        <joint type="free" damping="0" armature="0" limited="false"/>
    </default>     
</default>

<statistic extent="0.4" center="0 -0.2 0.2"/>

<visual>
    <quality shadowsize="2048"/>
    <map fogstart="1" fogend="3" znear="0.05" force="0.002" stiffness="200"/>
    <headlight diffuse=".6 .6 .6" specular="0 0 0" active="1"/>
    <scale contactwidth="0.1" contactheight="0.03" forcewidth="0.05"/>
</visual>

<include file="assets.xml"/>

<asset>
    <mesh name="base"           file="Base.STL"/>
    <mesh name="forearm"        file="Forearm.STL"/>
    <mesh name="palm"           file="Palm.STL"/>
    <mesh name="thumbProximal"  file="Thumb_Proximal.STL"/>
    <mesh name="thumbDistal"    file="Thumb_Distal.STL"/>
    <mesh name="thumbNail"      file="Thumb_Nail.STL"/>
    <mesh name="indexProximal"  file="Index_Proximal.STL"/>
    <mesh name="indexDistal0"   file="Index_Distal0.STL"/>
    <mesh name="indexDistal1"   file="Index_Distal1.STL"/>
    <mesh name="indexNail"      file="Index_Nail.STL"/>
    <mesh name="middleProximal" file="Middle_Proximal.STL"/>
    <mesh name="middleMedian"   file="MiddleRing_Median.STL"/>
    <mesh name="middleDistal"   file="MiddleRing_Distal.STL"/>
    <mesh name="middleNail"     file="MiddleRing_Nail.STL"/>
    <mesh name="ringProximal"   file="Ring_Proximal.STL"/>
    <mesh name="littleProximal" file="Pinky_Proximal.STL"/>
    <mesh name="littleDistal0"  file="Pinky_Distal0.STL"/>
    <mesh name="littleDistal1"  file="Pinky_Distal1.STL"/>
    <mesh name="littleNail"     file="Pinky_Nail.STL"/>
</asset>

<contact>       
    <pair geom1="palm" geom2="thumbProximal"/>
</contact>

<worldbody>
    <light directional="false" cutoff="35" exponent="10" diffuse=".7 .7 .7" pos="0.4 -0.2 1.5" dir="-0.4 0.2 -1.5" specular=".3 .3 .3"/>

    <!-- ======= TABLE ======= -->
    <geom name="ground" type="plane" material="table2d" pos="0 0 0" size=".5 .5 .025" condim="1"/>
    <geom contype="0" conaffinity="0" type="box" material="tablecube" pos="0 0 -0.026" size=".5 .5 .025"/>
    <geom contype="0" conaffinity="0" type="cylinder" fromto=".4 .4 -1.001 .4 .4 -0.002" size="0.04"/>
    <geom contype="0" conaffinity="0" type="cylinder" fromto="-.4 .4 -1.001 -.4 .4 -0.002" size="0.04"/>
    <geom contype="0" conaffinity="0" type="cylinder" fromto=".4 -.4 -1.001 .4 -.4 -0.002" size="0.04"/>
    <geom contype="0" conaffinity="0" type="cylinder" fromto="-.4 -.4 -1.001 -.4 -.4 -0.002" size="0.04"/>
    <geom contype="0" conaffinity="0" type="plane" pos="0 0 -1" size="10 10 0.25" material="groundplane"/>

    <!-- ======= MOCAP ======= -->
    <body name="tracker" mocap="true" pos="0 -0.35 0.2" euler="90 0 0">
        <geom type="cylinder" group="1" size="0.04 0.01" contype="0" conaffinity="0" rgba=".9 .5 .5 1"/>
    </body>

    <!-- ======= ROBOT ======= -->
    <body name="base" childclass="robot" pos="0 -0.35 0.2" euler="90 180 30">
        <joint name="base" class="free"/>
        <geom type="mesh" mesh="base" group="2"/>
        
        <body name="forearm" pos="0 0 0">
            <joint name="wristRotation" axis="0 0 -1" armature="0.05" damping="2" range="-120 175" frictionloss="1"/>
            <geom type="mesh" mesh="forearm" group="2"/>

            <body name="wrist" pos="0 0 0.09255" euler="0 -13 0">
                <joint name="wristDeviation" axis="0 1 0" damping="0.2" limited="true" range="-20 20"/>
                <geom type="sphere" size="0.01" group="2"/>
            
                <body name="palm" pos="0 0 0" euler="0 0 30">
                    <joint name="wristFlexion" axis="1.7321 -1 0" armature="0.05" damping="2" range="-55 55" frictionloss="1"/>
                    <geom name="palm" type="mesh" mesh="palm"/>
                    <geom type="capsule" fromto="0.038 -0.007 0.045  0.028 -0.003 0.041" size="0.018"/>
                    <site name="palmProximal" pos="-0.005 -.018 .042" size=".025 .003 .013"/>
                    <site name="palmDistal" pos="-0.003 -.018 .075" size=".032 .003 .02"/>
                    <site name="handDorsal" pos="0 .018 .07" size=".035 .003 .025"/>
                    <site name="handEdge"  pos="-0.04 0 .07" size=".003 .015 .025"/>

                    <!--THUMB-->
                    <body name="thumbBase" pos="0.0425 -0.01408 0.045">
                        <joint name="thumbYaw" axis="-1 0 0" range="0 90" frictionloss="0.5"/>
                        <geom type="sphere" size="0.007"/>

                        <body name="thumb" pos="0 0 0" euler="0 0 -10">
                            <joint name="thumbPitch" axis="0 0 -1" range="0 100" frictionloss="0.5"/>
                            <geom type="capsule" fromto="0.005 0.007 0 0.025 0.007 0" size="0.013" />
                            <geom name="thumbProximal" type="mesh" mesh="thumbProximal" contype="3"/>
                            <geom name="thumbDistal" type="mesh" mesh="thumbDistal" contype="3"/>
                            <geom name="thumbNail" type="mesh" pos="0 0 0.0007" mesh="thumbNail" contype="3" condim="1"/>
                            <site name="thumbTip" pos="0.07 0.007 0.01" size=".032 .01 .003"/>
                            <site name="thumbRadial" pos="0.07 -0.002 0" size=".032 .003 .01"/>
                            <site name="thumbDorsal" pos="0.075 0.007 -0.01" size=".037 .01 .003"/>
                            <site name="thumbUlnar" pos="0.07 0.016 0" size=".032 .003 .01"/>
                        </body>
                    </body>

                    <!--INDEX-->
                    <body name="indexProximal" pos="0.0299 -0.00108 0.100">
                        <joint name="indexProximal"/>
                        <geom type="mesh" mesh="indexProximal"/>

                        <body name="indexDistal" pos="0 0 .040">
                            <joint name="indexDistal"/>
                            <geom type="mesh" mesh="indexDistal0"/>
                            <geom name="indexDistal" type="mesh" mesh="indexDistal1"/>
                            <geom name="indexNail" type="mesh" mesh="indexNail" condim="1"/>
                            <site name="indexTip" pos="0 -.008 .03" size=".008 .003 .018"/>
                            <site name="indexLateral" pos="0.008 0 0.028" size=".003 .006 .02"/>
                        </body>
                    </body>
                        
                    <!--MIDDLE-->
                    <body name="middleProximal" pos="0.0095 -0.00108 0.100">
                        <joint name="middleProximal"/>
                        <geom type="mesh" mesh="middleProximal"/>

                        <body name="middleDistal" pos="0 0 .0443">
                            <joint name="middleDistal"/>
                            <geom type="mesh" mesh="middleMedian"/>
                            <geom type="mesh" mesh="middleDistal" pos="0 0 .025" axisangle="1 0 0 15"/>
                            <geom name="middleNail" type="mesh" mesh="middleNail" pos="0 0 .025" axisangle="1 0 0 15" condim="1"/>
                            <site name="middleTip" pos="0 -.01 .03" size=".008 .003 .02"/>
                        </body>
                    </body>
                    
                    <!--RING-->
                    <body name="ringProximal" childclass="RP" pos="-0.0095 -0.00108 0.100">
                        <joint name="ringProximal"/>
                        <geom type="mesh" mesh="ringProximal"/>
                        
                        <body name="ringDistal" pos="0 0 .03807">
                            <joint name="ringDistal"/>
                            <geom type="mesh" mesh="middleMedian"/> 
                            <geom name="ringDistal" type="mesh" mesh="middleDistal" pos="0 0 .025" axisangle="1 0 0 15"/>
                            <geom name="ringNail" type="mesh" mesh="middleNail" pos="0 0 .025" axisangle="1 0 0 15" condim="1"/>
                            <site name="ringTip" pos="0 -.01 .03" size=".008 .003 .02"/>
                        </body>
                    </body>
                    
                    <!--LITTLE-->
                    <body name="littleProximal" childclass="RP" pos="-0.0285 -0.00108 0.09598">
                        <joint name="littleProximal"/>
                        <geom type="mesh" mesh="littleProximal"/>
                        
                        <body name="littleDistal" pos="0 0 .028">
                            <joint name="littleDistal"/>
                            <geom type="mesh" mesh="littleDistal0"/>
                            <geom type="mesh" mesh="littleDistal1"/>
                            <geom name="littleNail" type="mesh" pos="0 0.001 0" mesh="littleNail" condim="1"/>
                            <site name="littleTip" pos="0 -.01 .025" size=".008 .003 .015"/>
                        </body>
                    </body>
                </body>
            </body>         
        </body>
    </body>           
</worldbody>

<tendon>
    <fixed name="index" frictionloss="1">
        <joint joint="indexProximal"  coef="0.5"/>
        <joint joint="indexDistal"    coef="0.5"/>
    </fixed>

    <fixed name="MRP" frictionloss="2">
		<joint joint="middleProximal" coef="0.25"/>
		<joint joint="middleDistal"   coef="0.25"/>
		<joint joint="ringProximal"   coef="0.125"/>
		<joint joint="ringDistal"     coef="0.125"/>
		<joint joint="littleProximal" coef="0.125"/>
		<joint joint="littleDistal"   coef="0.125"/>
    </fixed>

    <fixed name="couple1">
		<joint joint="middleProximal" coef="1"/>
		<joint joint="middleDistal"   coef="-0.2"/>
		<joint joint="ringProximal"   coef="-0.2"/>
		<joint joint="ringDistal"     coef="-0.2"/>
		<joint joint="littleProximal" coef="-0.2"/>
		<joint joint="littleDistal"   coef="-0.2"/>
    </fixed>
    <fixed name="couple2">
		<joint joint="middleProximal" coef="-0.2"/>
		<joint joint="middleDistal"   coef="1"/>
		<joint joint="ringProximal"   coef="-0.2"/>
		<joint joint="ringDistal"     coef="-0.2"/>
		<joint joint="littleProximal" coef="-0.2"/>
		<joint joint="littleDistal"   coef="-0.2"/>
    </fixed>
    <fixed name="couple3">
		<joint joint="middleProximal" coef="-0.2"/>
		<joint joint="middleDistal"   coef="-0.2"/>
		<joint joint="ringProximal"   coef="1"/>
		<joint joint="ringDistal"     coef="-0.2"/>
		<joint joint="littleProximal" coef="-0.2"/>
		<joint joint="littleDistal"   coef="-0.2"/>
    </fixed>
    <fixed name="couple4">
		<joint joint="middleProximal" coef="-0.2"/>
		<joint joint="middleDistal"   coef="-0.2"/>
		<joint joint="ringProximal"   coef="-0.2"/>
		<joint joint="ringDistal"     coef="1"/>
		<joint joint="littleProximal" coef="-0.2"/>
		<joint joint="littleDistal"   coef="-0.2"/>
    </fixed>
    <fixed name="couple5">
		<joint joint="middleProximal" coef="-0.2"/>
		<joint joint="middleDistal"   coef="-0.2"/>
		<joint joint="ringProximal"   coef="-0.2"/>
		<joint joint="ringDistal"     coef="-0.2"/>
		<joint joint="littleProximal" coef="1"/>
		<joint joint="littleDistal"   coef="-0.2"/>
    </fixed>
    <fixed name="couple6">
		<joint joint="middleProximal" coef="-0.2"/>
		<joint joint="middleDistal"   coef="-0.2"/>
		<joint joint="ringProximal"   coef="-0.2"/>
		<joint joint="ringDistal"     coef="-0.2"/>
		<joint joint="littleProximal" coef="-0.2"/>
		<joint joint="littleDistal"   coef="1"/>
    </fixed>
</tendon>

<equality>
    <weld body1="tracker" body2="base" solimp="0.8 0.8 0.001" solref="0.01 1"/>

    <joint joint1="wristDeviation" joint2="wristFlexion" polycoef="-0.0057 0.0347 0.0352 -0.1023 0.0993"/>
    <joint joint1="indexProximal" joint2="indexDistal"/>

    <tendon class="couple" tendon1="couple1"/>
    <tendon class="couple" tendon1="couple2"/>
    <tendon class="couple" tendon1="couple3"/>
    <tendon class="couple" tendon1="couple4"/>
    <tendon class="couple" tendon1="couple5"/>
    <tendon class="couple" tendon1="couple6"/>
</equality>

<actuator>
    <position name="wristRotation" joint="wristRotation" ctrlrange="-175 120" forcerange="-0.3  0.3"  kp="0.02"/>
    <position name="wristFlexion"  joint="wristFlexion"  ctrlrange="-55 55"   forcerange="-0.3  0.3"  kp="0.02"/>
    <position name="thumbYaw"      joint="thumbYaw"      ctrlrange="0 90"     forcerange="-0.05 0.05" kp="0.01"/>
    <!-- <position name="thumbPitch"    joint="thumbPitch"    ctrlrange="89 100"    forcerange="-0.05 0.05" kp="0.01"/> -->
    <position name="thumbPitch"    joint="thumbPitch"    ctrlrange="0 100"    forcerange="-0.05 0.05" kp="0.01"/>

    <position name="index"         tendon="index"        ctrlrange="0 90"     forcerange="-0.1  0.1"  kp="0.02"/>
    <position name="MRP"           tendon="MRP"          ctrlrange="0 90"     forcerange="-0.2  0.2"  kp="0.04"/>
</actuator>

<sensor>
    <actuatorpos actuator="wristRotation" cutoff="175"/>
    <actuatorpos actuator="wristFlexion"  cutoff="55"/>
    <actuatorpos actuator="thumbYaw"      cutoff="90"/>
    <actuatorpos actuator="thumbPitch"    cutoff="100"/>
    <actuatorpos actuator="index"         cutoff="90"/>
    <actuatorpos actuator="MRP"           cutoff="90"/>

    <touch site="palmProximal" cutoff="25.5"/>
    <touch site="palmDistal"   cutoff="25.5"/>
    <touch site="handDorsal"   cutoff="25.5"/>
    <touch site="handEdge"     cutoff="25.5"/>
    <touch site="thumbTip"     cutoff="25.5"/>
    <touch site="thumbRadial"  cutoff="25.5"/>
    <!-- <touch site="thumbDorsal"  cutoff="25.5"/> -->
    <!-- <touch site="thumbUlnar"   cutoff="25.5"/> -->
    <touch site="indexTip"     cutoff="25.5"/>
    <touch site="indexLateral" cutoff="25.5"/>
    <touch site="middleTip"    cutoff="25.5"/>
    <touch site="ringTip"      cutoff="25.5"/>
    <touch site="littleTip"    cutoff="25.5"/>
</sensor>

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.