examples/mujoco_xr: pick the gripper ghost with --robot

.gitignore

@@ -69,13 +69,14 @@ deps/v2d/wheels/
 # Runtime device files injected by MCP server infrastructure
 .mcp.json
 
-# SO-101 leader-gripper assets, fetched by
-# examples/mujoco_xr/scripts/fetch-so-arm.sh into the package's own assets
-# directory (which is what makes them package data), so only the authored
-# wrapper XML beside them is tracked.
+# Gripper-ghost assets, fetched by examples/mujoco_xr/scripts/fetch-*.sh into the
+# package's own assets directory (which is what makes them package data), so only
+# the authored wrapper XML beside them is tracked.
 #
-# Keep this rule here, not in examples/mujoco_xr/.gitignore: scikit-build-core
+# Keep these rules here, not in examples/mujoco_xr/.gitignore: scikit-build-core
 # resolves .gitignore against the project root, so a rule there would strip the
 # meshes out of the wheel too.
 /examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/leader/*
 !/examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/leader/leader_gripper.xml
+/examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/rebot/*
+!/examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/rebot/rebot_gripper.xml

examples/mujoco_xr/cpp/mesh_buffers.hpp

@@ -9,7 +9,7 @@
 // Normals are computed here, not taken from mjModel: MuJoCo welds an STL's
 // vertices and stores one averaged normal per welded vertex (mesh_normalnum ==
 // mesh_vertnum, mesh_facenormal == mesh_face), so on a CAD part every crease
-// gets a normal smeared across it. Measured on the shipped scene under
+// gets a normal smeared across it. Measured on the SO-101 scene under
 // test_ghost.py's own predicate (dot(corner normal, own face normal) <= 0):
 // 2138 of Wrist_Roll_SO101's 18474 face corners point away from their own
 // face, and 9489 of the STS3215's 57240. Lit one-sided those corners drop to

examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/leader/leader_gripper.xml

@@ -4,7 +4,7 @@ SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All
 SPDX-License-Identifier: Apache-2.0
 
 The leader gripper ghost: an SO-101 leader gripper locked to the operator's
-controller grip pose, and the whole of the shipped scene. It shows the grip
+controller grip pose, and the whole of `--robot=so101`. It shows the grip
 calibration in app.py -- whether the tool sits in the hand the way a hand holds
 one. It cannot show cpp/frames.hpp: those constants place it and are undone when
 the renderer folds it back into the XR reference space.

examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/rebot/rebot_gripper.xml

@@ -0,0 +1,91 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+
+The reBot DevArm gripper ghost, locked to the operator's controller grip pose.
+The counterpart of leader/leader_gripper.xml, and the same three rules apply:
+opaque (so draw order is free), collision-free, mocap-only. Read that file's
+header for why.
+
+What differs is what the ghost IS. The SO-101 one is the leader device the
+operator's fist is closed around; the reBot leader is a back-driven arm on a
+table, so this is the FOLLOWER's parallel jaw -- the thing the controller
+commands. Its placement on the hand is therefore a convention rather than a
+measurement (robots.py:REBOT_EULER_GRIP_FROM_GHOST_DEG).
+
+Provenance: all seven meshes are Seeed-Projects/reBotArm_control_py at commit
+e56b035e335b2e8b8b333ed94860ac9e936b67ba, urdf/00-arm-rs_asm-v3/. Upstream
+declares MIT in its README.md and ships no LICENSE file; the hardware itself is
+Seeed-Projects/reBot-DevArm, CERN-OHL-W-2.0. Fetched, not vendored --
+scripts/fetch-rebot-arm.sh pulls them beside this file, checksum-verified, with
+the URDF and that README. Only this wrapper is tracked; the payload is
+gitignored at the repository root.
+
+No `scale`: these STLs are in METRES, unlike the SO-101 print parts beside them
+(a jaw measures 38 x 79 x 35 mm as authored). The whole assembly is 115k
+triangles, dominated by motor_7.
+
+Two mocap bodies for the jaws rather than one, even though a single rack drives
+both: they translate in opposite directions, so one rigid body cannot carry
+them.
+-->
+<mujoco model="rebot devarm gripper ghost">
+  <asset>
+    <!-- Paths are relative to THIS file's directory; see leader_gripper.xml. -->
+    <mesh name="rebot_cover" file="pla7_green.STL"/>
+    <mesh name="rebot_rail" file="cnc7.STL"/>
+    <mesh name="rebot_motor" file="motor_7.STL"/>
+    <mesh name="rebot_jaw_left" file="pla_left.STL"/>
+    <mesh name="rebot_finger_left" file="cnc_left.STL"/>
+    <mesh name="rebot_jaw_right" file="pla_right.STL"/>
+    <mesh name="rebot_finger_right" file="cnc_right.STL"/>
+    <material name="rebot_ghost" rgba="0.55 0.80 1.00 1"/>
+  </asset>
+
+  <worldbody>
+    <!-- The gripper_end link. Its three visuals are at the URDF's identity
+         origin, so they carry no pos/quat here.
+
+         `pos` is where the ghost sits until the first valid controller sample,
+         and is shared by all three bodies below: app.py rotates and slides them
+         about the root's frame rather than placing their origins, so the joint
+         offsets live in exactly one place (the geoms). -->
+    <body name="rebot_ghost" mocap="true" pos="0.12 0.16 0.22">
+      <geom name="rebot_ghost_cover" type="mesh" mesh="rebot_cover"
+            material="rebot_ghost" contype="0" conaffinity="0" mass="0" group="2"/>
+      <geom name="rebot_ghost_rail" type="mesh" mesh="rebot_rail"
+            material="rebot_ghost" contype="0" conaffinity="0" mass="0" group="2"/>
+      <!-- The drive motor, and the part the operator's fist is placed on. -->
+      <geom name="rebot_ghost_motor" type="mesh" mesh="rebot_motor"
+            material="rebot_ghost" contype="0" conaffinity="0" mass="0" group="2"/>
+    </body>
+
+    <!-- The two jaws. `quat` is joint_left's / joint_right's URDF rpy converted,
+         NOT copied: URDF rpy is fixed-axis Rz*Ry*Rx while MuJoCo `euler=` is
+         intrinsic Rx*Ry*Rz, and these origins have two non-zero angles, so the
+         same three numbers in `euler=` are a different rotation. Written exact
+         (+-0.5) where upstream's 1.5708 is pi/2 rounded; tests/test_ghost.py
+         checks these against the fetched URDF to 4 microradians.
+
+         app.py slides them along -+y of the root frame, which is where
+         joint_left's / joint_right's "0 0 1" axis lands. -->
+    <body name="rebot_ghost_left" mocap="true" pos="0.12 0.16 0.22">
+      <geom name="rebot_ghost_jaw_left" type="mesh" mesh="rebot_jaw_left"
+            material="rebot_ghost" pos="-0.041939 -0.000073385 0"
+            quat="0.5 0.5 -0.5 0.5" contype="0" conaffinity="0" mass="0" group="2"/>
+      <geom name="rebot_ghost_finger_left" type="mesh" mesh="rebot_finger_left"
+            material="rebot_ghost" pos="-0.041939 -0.000073385 0"
+            quat="0.5 0.5 -0.5 0.5" contype="0" conaffinity="0" mass="0" group="2"/>
+    </body>
+
+    <body name="rebot_ghost_right" mocap="true" pos="0.12 0.16 0.22">
+      <geom name="rebot_ghost_jaw_right" type="mesh" mesh="rebot_jaw_right"
+            material="rebot_ghost" pos="-0.041939 0.000073385 0"
+            quat="-0.5 0.5 0.5 0.5" contype="0" conaffinity="0" mass="0" group="2"/>
+      <geom name="rebot_ghost_finger_right" type="mesh" mesh="rebot_finger_right"
+            material="rebot_ghost" pos="-0.041939 0.000073385 0"
+            quat="-0.5 0.5 0.5 0.5" contype="0" conaffinity="0" mass="0" group="2"/>
+    </body>
+  </worldbody>
+</mujoco>

examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/rebot_scene.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+
+`--robot=rebot`: the reBot DevArm gripper ghost, and nothing else. Same shape as
+so101_scene.xml -- see that file for what a ghost-only scene can and cannot show,
+and for why the renderer draws mjGEOM_MESH only.
+-->
+<mujoco model="mujoco_xr_rebot_scene">
+  <!-- timestep only. No <visual><headlight>: this scene is not lit by MuJoCo.
+       cpp/shaders/scene.frag has one hardcoded directional light and
+       mjvGLCamera is bypassed, so lighting declared here is silently inert. -->
+  <option timestep="0.002"/>
+
+  <include file="rebot/rebot_gripper.xml"/>
+</mujoco>

examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/scene.xml → examples/mujoco_xr/python/isaacteleop_examples/mujoco_xr/assets/so101_scene.xml

@@ -3,9 +3,9 @@
 SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 SPDX-License-Identifier: Apache-2.0
 
-The shipped scene: the SO-101 leader gripper ghost, and nothing else. No ground
-plane and no static furniture -- this is an AR scene and passthrough is the
-background.
+`--robot=so101`, the default: the SO-101 leader gripper ghost, and nothing else.
+No ground plane and no static furniture -- this is an AR scene and passthrough is
+the background.
 
 What a ghost-only scene cannot show: the ghost is placed from the controller
 pose through mj_from_xr and rendered back through xr_from_mj, so both