Added a chain Box2D scripting example.

physics/box2d_chain_terrain/all.texture_profiles

@@ -0,0 +1,18 @@
+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_chain_terrain/box2D_V2.appmanifest

@@ -0,0 +1,95 @@
+platforms:
+  arm64-ios:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      frameworks: []
+      linkFlags: []
+  x86_64-ios:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      frameworks: []
+      linkFlags: []
+  armv7-android:
+    context:
+      excludeLibs: []
+      excludeJars: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []
+      jetifier: true
+  arm64-android:
+    context:
+      excludeLibs: []
+      excludeJars: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []
+      jetifier: true
+  arm64-osx:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      frameworks: []
+      linkFlags: []
+  x86_64-osx:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      frameworks: []
+      linkFlags: []
+  x86_64-linux:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []
+  arm64-linux:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []
+  x86-win32:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []
+  x86_64-win32:
+    context:
+      excludeLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []
+  wasm-web:
+    context:
+      excludeLibs: []
+      excludeJsLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []
+  wasm_pthread-web:
+    context:
+      excludeLibs: []
+      excludeJsLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: []
+      linkFlags: []

physics/box2d_chain_terrain/box2D_V3.appmanifest

@@ -0,0 +1,100 @@
+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:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      frameworks: []
+      linkFlags: []
+  armv7-android:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeJars: []
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      linkFlags: []
+      jetifier: true
+  arm64-android:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeJars: []
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      linkFlags: []
+      jetifier: true
+  arm64-osx:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      frameworks: []
+      linkFlags: []
+  x86_64-osx:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      frameworks: []
+      linkFlags: []
+  x86_64-linux:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      linkFlags: []
+  arm64-linux:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      linkFlags: []
+  x86-win32:
+    context:
+      excludeLibs: [libphysics, libbox2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [libphysics_2d.lib, libbox2d.lib, libscript_box2d.lib, libphysics_3d.lib]
+      linkFlags: []
+  x86_64-win32:
+    context:
+      excludeLibs: [libphysics, libbox2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [libphysics_2d.lib, libbox2d.lib, libscript_box2d.lib, libphysics_3d.lib]
+      linkFlags: []
+  wasm-web:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeJsLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      linkFlags: []
+  wasm_pthread-web:
+    context:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeJsLibs: []
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      linkFlags: []

physics/box2d_chain_terrain/example.md

@@ -0,0 +1,47 @@
+---
+tags: physics, box2d
+title: Box2D Chain Terrain
+brief: Create Box2D chain terrain from script using scripting with Box2D V2 (legacy) and V3.
+author: Defold Foundation
+scripts: box2d_chain_terrain_v3.script, box2d_chain_terrain_v2.script
+thumbnail: thumbnail.webp
+---
+
+This example creates connected Box2D chain terrain 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 reset the ball and watch it roll over the same chain again.
+
+## What You'll Learn
+
+- How to get a Box2D body from a Defold collision object
+- How to detect the active Box2D version with `b2d.get_version()`
+- How to create chain terrain with `b2d.body.create_fixture()` in Box2D V2 Legacy Defold version.
+- How to create chain terrain with `b2d.body.create_chain()` in Box2D V3.
+
+## Setup
+
+The collection contains a static `terrain` game object with one collision object. This is required because the runtime-created terrain is attached to an existing Box2D body. Defold creates that body from the collision object in the collection.
+
+The small box shape on `terrain` sits below the view. It is only a placeholder that gives the script a static body to attach the runtime chain to; the visible terrain is the chain itself, drawn with `@render:draw_line`.
+
+The `controller` game object has both backend scripts, a label, and a local factory component named `ball_factory`. The factory points at `/example/ball.go`, a shared prototype with one sprite and one dynamic circle collision object.
+
+![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_chain_terrain_v2.script` only continues when the major version is 2 (Defold legacy version), while `box2d_chain_terrain_v3.script` only continues when the major version is 3.
+
+`b2d.get_body()` returns the Box2D body owned by the hidden `terrain` collision object. The active script then builds the chain with the backend-specific chain API.
+
+In Box2D V2 Legacy Defold version., the script passes a chain shape definition to `b2d.body.create_fixture()`, which creates connected segments on the same static body.
+
+In Box2D V3, the script uses `b2d.body.create_chain()`, which creates a true chain with segment adjacency and ghost vertices.
+
+The shape definition includes `prev_vertex` and `next_vertex`. These are ghost vertices placed just outside the first and last terrain points. They do not add visible terrain segments; they tell Box2D how the open chain would continue past its endpoints so endpoint collision normals stay consistent.
+
+The script redraws the chain vertices each frame with `@render:draw_line`, because the chain itself is a physics shape and has no sprite. The ball is created from the factory, given an initial velocity with `b2d.body.set_linear_velocity()`, and then reset on a timer or when the user clicks or taps.

physics/box2d_chain_terrain/example/ball.go

@@ -0,0 +1,43 @@
+embedded_components {
+  id: "sprite"
+  type: "sprite"
+  data: "default_animation: \"ball\"\n"
+  "material: \"/builtins/materials/sprite.material\"\n"
+  "size {\n"
+  "  x: 254.0\n"
+  "  y: 254.0\n"
+  "}\n"
+  "textures {\n"
+  "  sampler: \"texture_sampler\"\n"
+  "  texture: \"/textures/textures.atlas\"\n"
+  "}\n"
+  ""
+  scale {
+    x: 0.5
+    y: 0.5
+  }
+}
+embedded_components {
+  id: "collisionobject"
+  type: "collisionobject"
+  data: "type: COLLISION_OBJECT_TYPE_DYNAMIC\n"
+  "mass: 0.5\n"
+  "friction: 0.4\n"
+  "restitution: 0.05\n"
+  "group: \"default\"\n"
+  "mask: \"default\"\n"
+  "embedded_collision_shape {\n"
+  "  shapes {\n"
+  "    shape_type: TYPE_SPHERE\n"
+  "    position {\n"
+  "    }\n"
+  "    rotation {\n"
+  "    }\n"
+  "    index: 0\n"
+  "    count: 1\n"
+  "  }\n"
+  "  data: 31.5\n"
+  "}\n"
+  "angular_damping: 0.02\n"
+  ""
+}

physics/box2d_chain_terrain/example/box2d_chain_terrain.collection

@@ -0,0 +1,70 @@
+name: "box2d_chain_terrain"
+scale_along_z: 0
+embedded_instances {
+  id: "terrain"
+  data: "embedded_components {\n"
+  "  id: \"collisionobject\"\n"
+  "  type: \"collisionobject\"\n"
+  "  data: \"type: COLLISION_OBJECT_TYPE_STATIC\\n"
+  "mass: 0.0\\n"
+  "friction: 0.65\\n"
+  "restitution: 0.0\\n"
+  "group: \\\"default\\\"\\n"
+  "mask: \\\"default\\\"\\n"
+  "embedded_collision_shape {\\n"
+  "  shapes {\\n"
+  "    shape_type: TYPE_BOX\\n"
+  "    position {\\n"
+  "      x: 360.0\\n"
+  "      y: -120.0\\n"
+  "    }\\n"
+  "    rotation {\\n"
+  "    }\\n"
+  "    index: 0\\n"
+  "    count: 3\\n"
+  "  }\\n"
+  "  data: 10.0\\n"
+  "  data: 10.0\\n"
+  "  data: 10.0\\n"
+  "}\\n"
+  "event_collision: false\\n"
+  "event_contact: false\\n"
+  "event_trigger: false\\n"
+  "\"\n"
+  "}\n"
+  ""
+}
+embedded_instances {
+  id: "controller"
+  data: "components {\n"
+  "  id: \"box2d_v2\"\n"
+  "  component: \"/example/box2d_chain_terrain_v2.script\"\n"
+  "}\n"
+  "components {\n"
+  "  id: \"box2d_v3\"\n"
+  "  component: \"/example/box2d_chain_terrain_v3.script\"\n"
+  "}\n"
+  "embedded_components {\n"
+  "  id: \"label\"\n"
+  "  type: \"label\"\n"
+  "  data: \"size {\\n"
+  "  x: 640.0\\n"
+  "  y: 100.0\\n"
+  "}\\n"
+  "text: \\\"Click or touch to reset\\\"\\n"
+  "font: \\\"/fonts/text28.font\\\"\\n"
+  "material: \\\"/builtins/fonts/label-df.material\\\"\\n"
+  "\"\n"
+  "  position {\n"
+  "    x: 360.0\n"
+  "    y: 660.0\n"
+  "  }\n"
+  "}\n"
+  "embedded_components {\n"
+  "  id: \"ball_factory\"\n"
+  "  type: \"factory\"\n"
+  "  data: \"prototype: \\\"/example/ball.go\\\"\\n"
+  "\"\n"
+  "}\n"
+  ""
+}