Added motor joint example for Box2D v2 and v3.

physics/box2d_motor_joint/all.texture_profiles

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+path_settings {
+  path: "**"
+  profile: "Default"
+}
+profiles {
+  name: "Default"
+  platforms {
+    os: OS_ID_GENERIC
+    formats {
+      format: TEXTURE_FORMAT_RGBA
+      compression_level: BEST
+      compression_type: COMPRESSION_TYPE_DEFAULT
+    }
+    mipmaps: false
+    max_texture_size: 0
+    premultiply_alpha: true
+  }
+}

physics/box2d_motor_joint/box2D_V2.appmanifest

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+      jetifier: true
+  arm64-android:
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+      jetifier: true
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+  x86_64-win32:
+    context:
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+      symbols: []
+      libs: []
+      linkFlags: []
+  wasm-web:
+    context:
+      excludeLibs: []
+      excludeJsLibs: []
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+      linkFlags: []
+  wasm_pthread-web:
+    context:
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+      linkFlags: []

physics/box2d_motor_joint/box2D_V3.appmanifest

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+platforms:
+  armv7-ios:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+  arm64-ios:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      frameworks: []
+      linkFlags: []
+  x86_64-ios:
+    context:
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+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      frameworks: []
+      linkFlags: []
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+    context:
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+    context:
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+      libs: [libphysics_2d.lib, libbox2d.lib, libscript_box2d.lib, libphysics_3d.lib]
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+    context:
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+      libs: [libphysics_2d.lib, libbox2d.lib, libscript_box2d.lib, libphysics_3d.lib]
+      linkFlags: []
+  wasm-web:
+    context:
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+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
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+  wasm_pthread-web:
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physics/box2d_motor_joint/example.md

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+---
+tags: physics, box2d
+title: Box2D Motor Joint
+brief: Create and control a motorized Box2D joint from script using Box2D V2 and V3.
+author: Defold Foundation
+scripts: box2d_motor_joint_v3.script, box2d_motor_joint_v2.script
+thumbnail: thumbnail.webp
+---
+
+This example creates a motorized Box2D joint at runtime. It works with both Box2D V2 and V3 by attaching one script for each backend. Each script checks `b2d.get_version()` during `init()` and becomes a no-op when the other backend is active.
+
+Click or tap the window to reverse the motor direction.
+
+## What You'll Learn
+
+- How to get Box2D body handles from Defold collision objects
+- How to detect the active Box2D version with `b2d.get_version()`
+- How to create a pivoted motor joint with `b2d.joint.create_revolute()`
+- How to control joint motor speed with `b2d.joint.set_motor_speed()`
+- How to tune the Box2D V3 joint solver with `b2d.world.set_joint_tuning()`
+
+## Setup
+
+The collection contains a static `pivot` game object, one dynamic `arm` game object with a particle effect, and a controller game object.
+
+The `pivot` object marks the world point the arm should rotate around. The `arm` object is the dynamic body driven by the joint. The example uses a revolute joint with its motor enabled, because the revolute joint provides a stable hinge pivot while the motor drives the rotation.
+
+The controller has both backend scripts attached. Each script checks `b2d.get_version()` and only runs when the selected app manifest matches its Box2D backend.
+
+![setup](setup.png)
+
+The `game.project` of this example is configured to build with `/box2D_V3.appmanifest` by default. To test V2 locally after downloading the example, change `Native Extensions -> App Manifest` in `game.project` to `/box2D_V2.appmanifest`.
+
+![game_project](game_project.png)
+
+## How It Works
+
+Both scripts read `b2d.get_version()` once. `box2d_motor_joint_v2.script` only continues when the major version is 2, while `box2d_motor_joint_v3.script` only continues when the major version is 3.
+
+`b2d.get_body()` returns the Box2D bodies owned by the `pivot` and `arm` collision objects. The active script then creates a revolute joint between those bodies with `b2d.joint.create_revolute()`.
+
+The joint definition uses:
+
+- `local_anchor_a` on the pivot body
+- `local_anchor_b` on the arm body
+- `enable_motor` to turn on the joint motor
+- `max_motor_torque` to limit how strongly the motor can rotate the arm
+- `motor_speed` to set the current motor direction and speed
+
+The important part is the arm anchor. The pivot is placed in the collection as a visible reference point. The scripts convert that world position into the arm's local space, so the arm rotates around the same visible pivot instead of rotating around its center.
+
+Click or tap to reverse the motor with `b2d.joint.set_motor_speed()`. The V3 script also calls `b2d.world.set_joint_tuning()` to adjust the joint solver used by the Box2D V3 backend.

physics/box2d_motor_joint/example/arm.go

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+components {
+  id: "trail"
+  component: "/particlefx/trail.particlefx"
+  position {
+    x: 90.0
+    z: -0.1
+  }
+}
+components {
+  id: "play"
+  component: "/particlefx/play.script"
+}
+embedded_components {
+  id: "sprite"
+  type: "sprite"
+  data: "default_animation: \"pixel_blue\"\n"
+  "material: \"/builtins/materials/sprite.material\"\n"
+  "size {\n"
+  "  x: 200.0\n"
+  "  y: 40.0\n"
+  "}\n"
+  "size_mode: SIZE_MODE_MANUAL\n"
+  "textures {\n"
+  "  sampler: \"texture_sampler\"\n"
+  "  texture: \"/textures/textures.atlas\"\n"
+  "}\n"
+  ""
+}
+embedded_components {
+  id: "collisionobject"
+  type: "collisionobject"
+  data: "type: COLLISION_OBJECT_TYPE_DYNAMIC\n"
+  "mass: 3.0\n"
+  "friction: 0.4\n"
+  "restitution: 0.0\n"
+  "group: \"default\"\n"
+  "mask: \"default\"\n"
+  "embedded_collision_shape {\n"
+  "  shapes {\n"
+  "    shape_type: TYPE_BOX\n"
+  "    position {\n"
+  "    }\n"
+  "    rotation {\n"
+  "    }\n"
+  "    index: 0\n"
+  "    count: 3\n"
+  "  }\n"
+  "  data: 100.0\n"
+  "  data: 20.0\n"
+  "  data: 10.0\n"
+  "}\n"
+  "linear_damping: 0.05\n"
+  "angular_damping: 0.2\n"
+  ""
+}

physics/box2d_motor_joint/example/box2d_motor_joint.collection

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+name: "box2d_motor_joint"
+instances {
+  id: "pivot"
+  prototype: "/example/pivot.go"
+  position {
+    x: 360.0
+    y: 360.0
+    z: 0.5
+  }
+}
+instances {
+  id: "arm"
+  prototype: "/example/arm.go"
+  position {
+    x: 480.0
+    y: 360.0
+  }
+}
+scale_along_z: 0
+embedded_instances {
+  id: "controller"
+  data: "components {\n"
+  "  id: \"box2d_v2\"\n"
+  "  component: \"/example/box2d_motor_joint_v2.script\"\n"
+  "}\n"
+  "components {\n"
+  "  id: \"box2d_v3\"\n"
+  "  component: \"/example/box2d_motor_joint_v3.script\"\n"
+  "}\n"
+  "embedded_components {\n"
+  "  id: \"label\"\n"
+  "  type: \"label\"\n"
+  "  data: \"size {\\n"
+  "  x: 640.0\\n"
+  "  y: 96.0\\n"
+  "}\\n"
+  "text: \\\"Box2D motor joint\\\"\\n"
+  "font: \\\"/fonts/text28.font\\\"\\n"
+  "material: \\\"/builtins/fonts/label-df.material\\\"\\n"
+  "\"\n"
+  "  position {\n"
+  "    x: 360.0\n"
+  "    y: 60.0\n"
+  "  }\n"
+  "}\n"
+  ""
+}