Beta: components are the MuJoCo model

.clang-format

@@ -5,6 +5,13 @@
 # CoreUObject/Public/VerseVM/.clang-format), with ONE deliberate deviation:
 #
 # SortIncludes: false
+# LineEnding: LF
+#
+# Epic's config leaves the line ending to whatever the file already has, which
+# on Windows means clang-format preserves the CRLF that core.autocrlf wrote.
+# Pinning it makes the formatter normalise, so a file formatted on Windows and
+# one formatted on Linux are the same bytes. `.gitattributes` pins the same
+# thing for the repository; this is the half that runs before a commit exists.
 #
 # Epic ships SortIncludes: true, but those engine subsystems have no
 # reflection/generated headers. URLab's UPROPERTY modules require the
@@ -62,6 +69,7 @@ IndentCaseLabels: true
 IndentPPDirectives: None
 IndentWidth: 4
 Language: Cpp
+LineEnding: LF
 NamespaceIndentation: None
 PackConstructorInitializers: CurrentLine
 PointerAlignment: Left

.git-blame-ignore-revs

@@ -6,3 +6,6 @@
 
 # style: adopt Epic clang-format + codegen format-step + repo reformat
 1a57be12debd08eb60a2db0a5503b0a64c8ad678
+
+# style: reformat hand-written sources and pin line endings to LF
+3381d8597bbb3106d826d6ffb369a82fce531ffb

.gitattributes

@@ -0,0 +1,35 @@
+# Line endings are LF in the repository and LF on checkout, on every platform.
+#
+# Without this, `core.autocrlf=true` (the Windows default) commits CRLF, and a
+# file touched on Windows shows up as changed in its entirety on Linux and in
+# review. Pinning it here rather than asking every contributor to configure
+# their client is what keeps that out of the history.
+* text=auto eol=lf
+
+# Binary, and never to be sniffed for it. Content sniffing gets these right
+# today; saying so outright means it cannot get them wrong after an edit that
+# happens to remove every NUL byte from a header.
+*.png binary
+*.uasset binary
+*.umap binary
+*.stl binary
+*.obj binary
+*.mjb binary
+
+# The emitted MuJoCo document profile.
+#
+# LF-pinned because the drift gate compares generated bytes: on Windows,
+# core.autocrlf would rewrite these on checkout and the next `--check` would
+# report a difference that is nothing but line endings. Marked generated so
+# review tools collapse them and language statistics ignore them.
+Source/URLab/Public/MuJoCo/Gen/** text eol=lf linguist-generated=true
+Source/URLab/Private/MuJoCo/Gen/** text eol=lf linguist-generated=true
+Source/URLabEditor/Private/Tests/MjGenCoverage.gen.cpp text eol=lf linguist-generated=true
+Scripts/regen_ue_profile.ps1 text eol=lf
+Scripts/regen_ue_profile.sh text eol=lf
+
+# Recorded models. These are compared field for field after being loaded back,
+# so any rewriting on checkout would surface as a corrupt golden rather than as
+# the line-ending change it actually was. Pinned rather than left to content
+# sniffing, because a golden is only worth what its bytes are.
+Content/TestData/goldens/*.mjb binary

.gitignore

@@ -34,6 +34,7 @@ ThirdParty
 *.lo
 *.o
 *.obj
+!Content/TestData/**/*.obj
 
 # Precompiled Headers
 *.gch
@@ -119,6 +120,9 @@ third_party/install/
 # submodule checkout itself is tracked via the submodule pointer; only the
 # per-build scratch directories inside each submodule are ignored.
 third_party/*/src/build/
+# Per-dep build scratch dirs that sit beside src/ rather than inside it
+# (e.g. third_party/MjShim/build/).
+third_party/*/build/
 
 # Python cache
 __pycache__/

.gitmodules

@@ -1,5 +1,7 @@
 [submodule "third_party/MuJoCo/src"]
 	path = third_party/MuJoCo/src
+	# Upstream MuJoCo. The engine is built from it, and the ProtoSpec generator
+	# reads src/xml/mjcf.schema and doc/generate/mjcf_schema.py from it.
 	url = https://github.com/google-deepmind/mujoco
 [submodule "third_party/CoACD/src"]
 	path = third_party/CoACD/src

Content/TestData/boundary/plugins.xml

@@ -0,0 +1,19 @@
+<mujoco model="plugins">
+<!-- a built-in engine plugin instance (cable elasticity) activated via extension and used by a composite -->
+ <extension>
+ <plugin plugin="mujoco.elasticity.cable">
+ <instance name="cable_inst">
+ <config key="twist" value="1e7"/>
+ <config key="bend" value="4e6"/>
+ </instance>
+ </plugin>
+ </extension>
+
+ <worldbody>
+ <composite type="cable" curve="s" count="5 1 1" size="0.5" offset="0 0 1" initial="none">
+ <plugin plugin="mujoco.elasticity.cable" instance="cable_inst"/>
+ <joint kind="main" damping="0.01"/>
+ <geom type="capsule" size="0.005"/>
+ </composite>
+ </worldbody>
+</mujoco>

Content/TestData/goldens/CAPTURE.json

@@ -0,0 +1,6 @@
+{
+ "mujoco_version": "3.11.1",
+ "mujoco_submodule": "b6683ac13dd353c8d66788a3beea6e84b2eb2dc2",
+ "captured_commit": "8028138e0e5f68fafd2b9b53ff958ad29cb27195",
+ "captured_utc": "2026-08-09"
+}

Content/TestData/goldens/actuators_all.roundtrip.xml

@@ -0,0 +1,33 @@
+<mujoco model="actuators_all">
+ <worldbody>
+ <site name="site_ref" pos="0 0 0"/>
+ <body name="link1" pos="0 0 1">
+ <joint name="j1" type="hinge" axis="0 0 1"/>
+ <geom name="geom_link1" type="capsule" size="0.05 0.25" pos="0.25 0 0" quat="0.7071067811865476 0 -0.7071067811865476 0"/>
+ <site name="site1" pos="0.5 0 0"/>
+ <body name="link2" pos="0.5 0 0">
+ <joint name="j2" type="hinge" axis="0 1 0"/>
+ <geom name="geom_link2" type="capsule" size="0.05 0.25" pos="0.25 0 0" quat="0.7071067811865476 0 -0.7071067811865476 0"/>
+ </body>
+ </body>
+ </worldbody>
+ <tendon>
+ <fixed name="ftendon">
+ <joint joint="j1" coef="1"/>
+ </fixed>
+ </tendon>
+ <actuator>
+ <general name="act_general" tendon="ftendon" gaintype="affine" biastype="affine" gainprm="2 0 0" biasprm="0 -10 -1"/>
+ <motor name="act_motor" joint="j1"/>
+ <position name="act_position" joint="j1" kp="10" dampratio="1"/>
+ <velocity name="act_velocity" joint="j1" kv="0.5"/>
+ <intvelocity name="act_intvelocity" actrange="-1 1" joint="j2" kp="10" kv="0.5"/>
+ <orientation name="act_orientation" site="site1" refsite="site_ref" kp="5" kv="0.5"/>
+ <pid name="act_pid" joint="j2" kp="10" kv="0.25" ki="0.5" imax="1"/>
+ <damper name="act_damper" ctrlrange="0 1" joint="j1" kv="0.5"/>
+ <cylinder name="act_cylinder" joint="j2" timeconst="0.5" area="0.04908738521234052" bias="0 -1 0"/>
+ <muscle name="act_muscle" lengthrange="0.2 0.6" joint="j1" timeconst="0.01 0.04" range="0.75 1.25" force="1"/>
+ <adhesion name="act_adhesion" ctrlrange="0 1" body="link2" gain="1"/>
+ <dcmotor name="act_dcmotor" joint="j2" motorconst="0.5 0.25" resistance="1"/>
+ </actuator>
+</mujoco>

Content/TestData/goldens/angle_degrees.roundtrip.xml

@@ -0,0 +1,13 @@
+<mujoco model="angle_degrees">
+ <compiler angle="degree" eulerseq="zyx"/>
+ <worldbody>
+ <body name="body_euler" pos="0 0 1" quat="0.8223631719059994 0.3604234056503559 0.43967973954090955 0.022260026714733816">
+ <joint name="j_euler" type="hinge" axis="0 0 1" stiffness="1" range="-90 90" ref="15" springref="30"/>
+ <geom name="geom_euler" type="box" size="0.1 0.1 0.1"/>
+ <body name="body_axisangle" pos="0.5 0 0" quat="0.7071067811865476 0 0 0.7071067811865476">
+ <joint name="j_axisangle" type="hinge" axis="1 0 0" stiffness="1" range="-45 45" ref="10" springref="20"/>
+ <geom name="geom_axisangle" type="box" size="0.05 0.05 0.05"/>
+ </body>
+ </body>
+ </worldbody>
+</mujoco>

Content/TestData/goldens/assets_meshes.roundtrip.xml

@@ -0,0 +1,22 @@
+<mujoco model="assets_meshes">
+ <asset>
+ <mesh name="mesh_a" file="meshA/base.obj"/>
+ <mesh name="mesh_b" file="meshB/base.obj"/>
+ <hfield name="hf_small" nrow="2" ncol="2" size="1 1 0.5 0.1" elevation="0 0.25 0.5 0.75"/>
+ <texture name="tex_checker" type="2d" file="checker.png"/>
+ <material name="mat_checker" texrepeat="1 1">
+ <layer texture="tex_checker" role="rgb"/>
+ </material>
+ </asset>
+ <worldbody>
+ <geom name="geom_hfield" type="hfield" pos="0 0 0" hfield="hf_small"/>
+ <body name="body_mesh_a" pos="2 0 0.5">
+ <freejoint name="jf_mesh_a"/>
+ <geom name="geom_mesh_a" type="mesh" material="mat_checker" mesh="mesh_a"/>
+ </body>
+ <body name="body_mesh_b" pos="4 0 0.5">
+ <freejoint name="jf_mesh_b"/>
+ <geom name="geom_mesh_b" type="mesh" material="mat_checker" mesh="mesh_b"/>
+ </body>
+ </worldbody>
+</mujoco>

Content/TestData/goldens/defaults_nested.roundtrip.xml

@@ -0,0 +1,38 @@
+<mujoco model="defaults_nested">
+ <default>
+ <default class="top">
+ <default class="mid">
+ <default class="leaf">
+ <joint damping="2"/>
+ <geom size="0.025 0.025 0.025" rgba="0.2 0.2 0.8 1"/>
+ <position kp="40"/>
+ </default>
+ <joint damping="1"/>
+ <geom size="0.05 0.05 0.05" rgba="0.2 0.8 0.2 1"/>
+ <position kp="20"/>
+ </default>
+ <joint type="hinge" damping="0.5"/>
+ <geom type="box" size="0.1 0.1 0.1" rgba="0.8 0.2 0.2 1"/>
+ <position kp="10"/>
+ </default>
+ </default>
+ <worldbody>
+ <body name="body_top" childclass="top" pos="0 0 1">
+ <geom name="geom_top"/>
+ <joint name="joint_top" axis="0 0 1"/>
+ <body name="body_mid" childclass="mid" pos="0.5 0 0">
+ <geom name="geom_mid"/>
+ <joint name="joint_mid" axis="0 1 0"/>
+ <body name="body_leaf" pos="0.25 0 0">
+ <geom name="geom_leaf" class="leaf"/>
+ <joint name="joint_leaf" class="leaf" axis="1 0 0"/>
+ </body>
+ </body>
+ </body>
+ </worldbody>
+ <actuator>
+ <position name="act_top" class="top" joint="joint_top"/>
+ <position name="act_mid" class="mid" joint="joint_mid"/>
+ <position name="act_leaf" class="leaf" joint="joint_leaf"/>
+ </actuator>
+</mujoco>

Content/TestData/goldens/keyframes_options.roundtrip.xml

@@ -0,0 +1,19 @@
+<mujoco model="keyframes_options">
+ <option timestep="0.005" gravity="0 0 -4.905" integrator="RK4" cone="elliptic" iterations="50">
+ <flag contact="disable" gravity="enable" energy="enable"/>
+ </option>
+ <size memory="1048576"/>
+ <worldbody>
+ <body name="body1" pos="0 0 1">
+ <joint name="j1" type="hinge" axis="0 0 1"/>
+ <geom name="geom1" type="box" size="0.1 0.1 0.1"/>
+ </body>
+ </worldbody>
+ <actuator>
+ <motor name="act1" joint="j1"/>
+ </actuator>
+ <keyframe>
+ <key name="key_home" qpos="0" ctrl="0"/>
+ <key name="key_quarter" time="0.5" qpos="0.25" ctrl="0.5"/>
+ </keyframe>
+</mujoco>

Content/TestData/goldens/macro_composite.roundtrip.xml

@@ -0,0 +1,16 @@
+<mujoco model="macro_composite">
+ <default>
+ <default class="cable_default">
+ <geom type="capsule" size="0.005" rgba="0.9 0.4 0.1 1"/>
+ </default>
+ </default>
+ <worldbody>
+ <body name="composite_root" childclass="cable_default" pos="0 0 1">
+ <geom name="composite_anchor" type="sphere" size="0.02"/>
+ <composite type="cable" count="8 1 1" initial="none" curve="s" size="0.5">
+ <joint kind="main" damping="0.015"/>
+ <geom type="capsule" size="0.005"/>
+ </composite>
+ </body>
+ </worldbody>
+</mujoco>

Content/TestData/goldens/macro_flexcomp.roundtrip.xml

@@ -0,0 +1,15 @@
+<mujoco model="macro_flexcomp">
+ <default>
+ <default class="flex_default">
+ <geom rgba="0.2 0.6 0.9 1"/>
+ </default>
+ </default>
+ <worldbody>
+ <body name="flex_root" childclass="flex_default" pos="0 0 2">
+ <geom name="flex_anchor" type="sphere" size="0.02"/>
+ <flexcomp name="cloth" type="grid" dim="2" count="4 4 1" spacing="0.1 0.1 0.1" radius="0.01" mass="1">
+ <edge equality="true"/>
+ </flexcomp>
+ </body>
+ </worldbody>
+</mujoco>

Content/TestData/goldens/macro_replicate.roundtrip.xml

@@ -0,0 +1,20 @@
+<mujoco model="macro_replicate">
+ <default>
+ <default class="rep_default">
+ <joint type="hinge" damping="0.1"/>
+ <geom type="capsule" size="0.02" rgba="0.1 0.7 0.3 1"/>
+ </default>
+ </default>
+ <worldbody>
+ <body name="anchor_body" pos="0 0 2">
+ <joint name="anchor_joint" type="hinge" axis="0 0 1"/>
+ <geom name="anchor_geom" type="capsule" size="0.02 0.1" pos="0.1 0 0" quat="0.7071067811865476 0 -0.7071067811865476 0"/>
+ </body>
+ <replicate count="3" offset="0.3 0 0" sep="_" childclass="rep_default">
+ <body name="rep_body" pos="0 0 1">
+ <joint name="rep_joint" axis="0 0 1"/>
+ <geom name="rep_geom" size="0.02 0.1" pos="0.1 0 0" quat="0.7071067811865476 0 -0.7071067811865476 0"/>
+ </body>
+ </replicate>
+ </worldbody>
+</mujoco>

Content/TestData/goldens/plugins.roundtrip.xml

@@ -0,0 +1,17 @@
+<mujoco model="plugins">
+ <extension>
+ <plugin plugin="mujoco.elasticity.cable">
+ <instance name="cable_inst">
+ <config key="twist" value="1e7"/>
+ <config key="bend" value="4e6"/>
+ </instance>
+ </plugin>
+ </extension>
+ <worldbody>
+ <composite type="cable" count="5 1 1" offset="0 0 1" initial="none" curve="s" size="0.5">
+ <joint kind="main" damping="0.01"/>
+ <geom type="capsule" size="0.005"/>
+ <plugin plugin="mujoco.elasticity.cable" instance="cable_inst"/>
+ </composite>
+ </worldbody>
+</mujoco>