Added Box2D scripting sensors example

physics/box2d_sensor_toggle/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_sensor_toggle/box2d_v2.appmanifest

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+      jetifier: true
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+  x86_64-win32:
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+  wasm-web:
+    context:
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+  wasm_pthread-web:
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physics/box2d_sensor_toggle/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:
+      excludeLibs: [physics, box2d_defold, script_box2d_defold]
+      excludeSymbols: []
+      symbols: []
+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      frameworks: []
+      linkFlags: []
+  armv7-android:
+    context:
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+    context:
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+  wasm-web:
+    context:
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+      libs: [physics_2d, box2d, script_box2d, physics_3d]
+      linkFlags: []
+  wasm_pthread-web:
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physics/box2d_sensor_toggle/example.md

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+---
+tags: physics, box2d
+title: Box2D Sensors
+brief: Create Box2D sensors from static collision shapes.
+author: Defold Foundation
+scripts: sensor_box2d_v3.script, sensor_box2d_v2.script, spawn.script
+thumbnail: thumbnail.webp
+---
+
+This example shows how to utilize the Box2D scripting API to operate with sensors (triggers).
+It spawns dynamic physics balls from slightly different random positions near the top of the scene,
+and gravity pulls each ball down, and these pass through two collision objects.
+
+## What You'll Learn
+
+- How to get a Box2D body from a collision object with `b2d.get_body()`.
+- How to turn a Box2D V2 fixture into a sensor with `b2d.fixture.set_sensor()`.
+- How to recreate a Box2D V3 shape as a sensor with `b2d.body.create_shape()`.
+- How to count V2 sensor overlaps from `trigger_response` enter/exit messages.
+- How to poll V3 sensor overlaps with `b2d.shape.get_sensor_overlaps()`.
+
+## Setup
+
+The collection contains one `controller` game object with `spawn.script` and a `ball_factory`.
+The factory creates `ball.go` - a small prototype with one sprite and one dynamic circle collision object.
+
+The two sensor game objects both contain:
+
+- `sensor_box2d_v3.script` - for Box2D V3 example handling
+- `sensor_box2d_v2.script` - for Box2D V2 example handling
+- A sprite, label, and static collision object with component id `collisionobject`.
+
+The collision objects are of type `Static` in the editor.
+
+All sensors use the `sensor` collision group and mask the `ball` group.
+The spawned ball belongs to the `ball` collision group and masks the `sensor` group,
+so the sensor overlaps only include spawned balls.
+
+![setup](setup.png)
+
+The `game.project` currently uses `/box2d_v3.appmanifest`.
+To test V2 locally, change `Native Extensions -> App Manifest` to `/box2d_v2.appmanifest`.
+Gravity set in `game.project` causes the falling motion.
+
+## How It Works
+
+The controller spawns a ball repeateadly with `factory.create()`.
+Each ball is spawned at a random X position near the center, and is deleted after a short delay.
+The spawned balls pass through the sensor's collision object shapes.
+
+Each sensor has two backend scripts (V2 and V3), but only one runs processing depending on a choosen Box2D version.
+Each script checks `b2d.get_version().major` in `init()` and returns immediately when the active backend does not match.
+
+At startup, the active Box2D script changes the static collision geometry into a sensor (trigger) through the `b2d` API.
+Box2D V2 and V3 expose this through different scripting APIs:
+
+- V2 uses fixtures and Defold trigger messages.
+- V3 uses shapes and can poll a sensor shape's current overlaps directly.
+
+In Box2D V2, `sensor_box2d_v2.script` gets the body with `b2d.get_body("#collisionobject")`,
+reads the first fixture with `b2d.body.get_fixtures()`, and calls `b2d.fixture.set_sensor()`,
+so the fixture no longer blocks the balls. V2 fixture sensors do not expose a `get_sensor_overlaps()` polling API.
+But Defold still sends `trigger_response` messages when another collision object enters or exits the sensor,
+and the script maintains a Lua table of current overlapping ball ids.
+
+In Box2D V3, `sensor_box2d_v3.script` uses the shape API.
+It reads the first editor-authored shape with `b2d.body.get_shapes()` and `b2d.shape.get_shape()`,
+destroys that solid shape, and creates a replacement with `b2d.body.create_shape()` using the same geometry and `sensor = true`.
+The V3 script then calls `b2d.shape.enable_sensor_events()` for the new sensor shape.
+In `update()`, it polls the current overlaps with `b2d.shape.get_sensor_overlaps()`.
+This returns shape info tables for the shapes currently overlapping the sensor.
+
+Both scripts gives us the same result: each sensor sprite scales up while at least one ball overlaps it,
+and the label shows the current overlap count reported by the active backend path.

physics/box2d_sensor_toggle/example/ball.go

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+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: 1.0\n"
+  "friction: 0.2\n"
+  "restitution: 0.0\n"
+  "group: \"ball\"\n"
+  "mask: \"sensor\"\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: 32.0\n"
+  "}\n"
+  ""
+}