feat: add look-at 3D example

movement/look_at_3d/.gitattributes

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+# Defold Protocol Buffer Text Files (https://github.com/github/linguist/issues/5091)
+*.animationset linguist-language=JSON5
+*.atlas linguist-language=JSON5
+*.camera linguist-language=JSON5
+*.collection linguist-language=JSON5
+*.collectionfactory linguist-language=JSON5
+*.collectionproxy linguist-language=JSON5
+*.collisionobject linguist-language=JSON5
+*.cubemap linguist-language=JSON5
+*.display_profiles linguist-language=JSON5
+*.factory linguist-language=JSON5
+*.font linguist-language=JSON5
+*.gamepads linguist-language=JSON5
+*.go linguist-language=JSON5
+*.gui linguist-language=JSON5
+*.input_binding linguist-language=JSON5
+*.label linguist-language=JSON5
+*.material linguist-language=JSON5
+*.mesh linguist-language=JSON5
+*.model linguist-language=JSON5
+*.particlefx linguist-language=JSON5
+*.render linguist-language=JSON5
+*.sound linguist-language=JSON5
+*.sprite linguist-language=JSON5
+*.spinemodel linguist-language=JSON5
+*.spinescene linguist-language=JSON5
+*.texture_profiles linguist-language=JSON5
+*.tilemap linguist-language=JSON5
+*.tilesource linguist-language=JSON5
+
+# Defold JSON Files
+*.buffer linguist-language=JSON
+
+# Defold GLSL Shaders
+*.fp linguist-language=GLSL
+*.vp linguist-language=GLSL
+
+# Defold Lua Files
+*.editor_script linguist-language=Lua
+*.render_script linguist-language=Lua
+*.script linguist-language=Lua
+*.gui_script linguist-language=Lua

movement/look_at_3d/.gitignore

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+/.editor_settings
+/.internal
+/build
+.externalToolBuilders
+.DS_Store
+Thumbs.db
+.lock-wscript
+*.pyc
+.project
+.cproject
+builtins

movement/look_at_3d/example.md

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+---
+title: Rotate 3D object towards the mouse cursor
+brief: Learn how to rotate a 3D object towards the mouse cursor.
+author_ids:
+  - evgenii-starostin
+scripts: turret_controller.script, camera_controller.script
+thumbnail: thumbnail.webp
+tags: movement
+---
+This example demonstrates how to rotate a 3D object towards the mouse cursor.
+
+## Project Structure
+```
+- camera.go
+  - camera
+  - camera_controller.script
+  floor.go
+  - floor
+  - floor_uv_scale.script
+  root.go
+    - turret.go
+      - turret
+      - turret_controller.script
+    - base
+```
+
+## How It Works
+First, the script that controls the rotation needs a reference to the active camera. This is done by sending a message in `init`:
+
+```lua
+	msg.post("/turret#turret_controller", "register_camera", {
+		url = msg.url("#camera")
+	})
+```
+
+In turret_controller.script we use the camera to build a picking ray - a line that starts at the camera and goes through the cursor position in the world:
+
+```lua
+-- z = 0 -> near plane, z = 1 -> far plane (normalized depth)
+local p0 = camera.screen_to_world(
+	vmath.vector3(self.mouse_x, self.mouse_y, 0),
+	self.camera_url
+)
+
+local p1 = camera.screen_to_world(
+	vmath.vector3(self.mouse_x, self.mouse_y, 1),
+	self.camera_url
+)
+
+local ray = p1 - p0
+```
+
+Then we intersect this ray with the horizontal plane at the turret's height (y = gun_pos.y):
+```lua
+go.update_world_transform()
+local gun_pos = go.get_world_position()
+
+-- avoid division by zero when the ray is parallel to the plane
+if math.abs(ray.y) < 0.00001 then
+	return
+end
+
+local t = (gun_pos.y - p0.y) / ray.y
+local target = p0 + ray * t
+```
+
+Finally, we compute the yaw angle from the turret to the target and rotate the object around the Y axis. atan2(dx, dz) assumes the model faces +Z at angle 0:
+```lua
+local dx = target.x - gun_pos.x
+local dz = target.z - gun_pos.z
+
+if math.abs(dx) + math.abs(dz) < 0.00001 then
+	return
+end
+
+local angle = math.atan2(dx, dz)
+
+go.set_rotation(
+	vmath.quat_rotation_y(angle)
+)
+```

movement/look_at_3d/game.project

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+[bootstrap]
+main_collection = /main/main.collectionc
+
+[script]
+shared_state = 1
+
+[display]
+width = 720
+height = 720
+high_dpi = 1
+
+[android]
+input_method = HiddenInputField
+
+[physics]
+gravity_y = -1000.0
+scale = 0.01
+
+[html5]
+scale_mode = no_scale
+
+[project]
+title = Look at 3D
+dependencies = 
+developer = 
+

movement/look_at_3d/input/game.input_binding

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+mouse_trigger {
+  input: MOUSE_BUTTON_1
+  action: "touch"
+}

movement/look_at_3d/main/camera_controller.script

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+function init(self)
+	msg.post("/turret#turret_controller", "register_camera", {
+		url = msg.url("#camera")
+	})
+end

movement/look_at_3d/main/floor_uv_scale.script

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+function init(self)
+	go.set("#floor", "uv_scale", vmath.vector4(10, 10, 0, 0))
+end

movement/look_at_3d/main/main.collection

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+name: "main"
+scale_along_z: 0
+embedded_instances {
+  id: "root"
+  children: "turret"
+  data: "embedded_components {\n"
+  "  id: \"base\"\n"
+  "  type: \"model\"\n"
+  "  data: \"mesh: \\\"/main/models/base.glb\\\"\\n"
+  "skeleton: \\\"/main/models/base.glb\\\"\\n"
+  "animations: \\\"/main/models/base.glb\\\"\\n"
+  "name: \\\"{{NAME}}\\\"\\n"
+  "materials {\\n"
+  "  name: \\\"default\\\"\\n"
+  "  material: \\\"/main/materials/static/unlit.material\\\"\\n"
+  "  textures {\\n"
+  "    sampler: \\\"tex0\\\"\\n"
+  "    texture: \\\"/main/images/colormap.png\\\"\\n"
+  "  }\\n"
+  "}\\n"
+  "\"\n"
+  "}\n"
+  ""
+}
+embedded_instances {
+  id: "camera"
+  data: "components {\n"
+  "  id: \"camera_controller\"\n"
+  "  component: \"/main/camera_controller.script\"\n"
+  "}\n"
+  "embedded_components {\n"
+  "  id: \"camera\"\n"
+  "  type: \"camera\"\n"
+  "  data: \"aspect_ratio: 1.0\\n"
+  "fov: 1.047\\n"
+  "near_z: 2.1\\n"
+  "far_z: 30.0\\n"
+  "auto_aspect_ratio: 1\\n"
+  "orthographic_zoom: 116.0\\n"
+  "\"\n"
+  "}\n"
+  ""
+  position {
+    y: 5.0
+    z: 6.0
+  }
+  rotation {
+    x: -0.34202015
+    w: 0.9396926
+  }
+}
+embedded_instances {
+  id: "turret"
+  data: "components {\n"
+  "  id: \"turret_controller\"\n"
+  "  component: \"/main/turret_controller.script\"\n"
+  "}\n"
+  "embedded_components {\n"
+  "  id: \"turret\"\n"
+  "  type: \"model\"\n"
+  "  data: \"mesh: \\\"/main/models/turret.glb\\\"\\n"
+  "skeleton: \\\"/main/models/turret.glb\\\"\\n"
+  "animations: \\\"/main/models/turret.glb\\\"\\n"
+  "name: \\\"{{NAME}}\\\"\\n"
+  "materials {\\n"
+  "  name: \\\"default\\\"\\n"
+  "  material: \\\"/main/materials/skinned/unlit_skinned.material\\\"\\n"
+  "  textures {\\n"
+  "    sampler: \\\"tex0\\\"\\n"
+  "    texture: \\\"/main/images/colormap.png\\\"\\n"
+  "  }\\n"
+  "}\\n"
+  "\"\n"
+  "}\n"
+  ""
+}
+embedded_instances {
+  id: "floor"
+  data: "components {\n"
+  "  id: \"floor_uv_scale\"\n"
+  "  component: \"/main/floor_uv_scale.script\"\n"
+  "}\n"
+  "embedded_components {\n"
+  "  id: \"floor\"\n"
+  "  type: \"model\"\n"
+  "  data: \"mesh: \\\"/builtins/assets/gltf/quad.gltf\\\"\\n"
+  "name: \\\"{{NAME}}\\\"\\n"
+  "materials {\\n"
+  "  name: \\\"default\\\"\\n"
+  "  material: \\\"/main/materials/static/unlit.material\\\"\\n"
+  "  textures {\\n"
+  "    sampler: \\\"tex0\\\"\\n"
+  "    texture: \\\"/main/images/texture_02.png\\\"\\n"
+  "  }\\n"
+  "}\\n"
+  "\"\n"
+  "}\n"
+  ""
+  rotation {
+    x: -0.70710677
+    w: 0.70710677
+  }
+  scale3 {
+    x: 100.0
+    y: 100.0
+  }
+}

movement/look_at_3d/main/materials/skinned/unlit_skinned.fp

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+#version 140
+
+in vec2 var_texcoord0;
+uniform mediump sampler2D tex0;
+out lowp vec4 final_color;
+uniform fs_uniforms
+{
+	mediump vec4 tint;
+};
+
+void main()
+{
+	vec4 tint_pm = vec4(tint.xyz * tint.w, tint.w);
+	vec4 color = texture(tex0, var_texcoord0.xy) * tint_pm;
+	final_color = color;
+}

movement/look_at_3d/main/materials/skinned/unlit_skinned.material

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+name: "unlit"
+tags: "model"
+vertex_program: "/main/materials/skinned/unlit_skinned.vp"
+fragment_program: "/main/materials/skinned/unlit_skinned.fp"
+vertex_space: VERTEX_SPACE_LOCAL
+vertex_constants {
+  name: "mtx_worldview"
+  type: CONSTANT_TYPE_WORLDVIEW
+}
+vertex_constants {
+  name: "mtx_proj"
+  type: CONSTANT_TYPE_PROJECTION
+}
+fragment_constants {
+  name: "tint"
+  type: CONSTANT_TYPE_USER
+  value {
+    x: 1.0
+    y: 1.0
+    z: 1.0
+    w: 1.0
+  }
+}
+samplers {
+  name: "tex0"
+  wrap_u: WRAP_MODE_CLAMP_TO_EDGE
+  wrap_v: WRAP_MODE_CLAMP_TO_EDGE
+  filter_min: FILTER_MODE_MIN_LINEAR
+  filter_mag: FILTER_MODE_MAG_LINEAR
+}

movement/look_at_3d/main/materials/skinned/unlit_skinned.vp

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+#version 140
+
+in highp vec4 position;
+in mediump vec2 texcoord0;
+in mediump vec4 bone_weights;
+in mediump vec4 bone_indices;
+
+out mediump vec2 var_texcoord0;
+
+uniform vs_uniforms
+{
+	mediump mat4 mtx_worldview;
+	mediump mat4 mtx_proj;
+	mediump vec4 animation_data;
+};
+
+#include "/builtins/materials/skinning.glsl"
+
+void main()
+{
+	vec4 skinned_position = get_skinned_position(position);
+
+	var_texcoord0 = texcoord0;
+
+	vec4 p = mtx_worldview * vec4(skinned_position.xyz, 1.0);
+	gl_Position = mtx_proj * p;
+}

movement/look_at_3d/main/materials/static/unlit.fp

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+#version 140
+
+
+in mediump vec2 var_texcoord0;
+uniform mediump sampler2D tex0;
+in highp mat4 var_view;
+
+out vec4 out_fragColor;
+
+uniform fs_uniforms
+{
+	mediump vec4 tint;
+};
+
+void main()
+{
+	// Pre-multiply alpha since all runtime textures already are
+	vec4 tint_pm = vec4(tint.xyz * tint.w, tint.w);
+
+	// Sample the texture at the fragment's texture coordinates.
+	vec4 color = texture(tex0, var_texcoord0.xy) * tint_pm;
+
+	// Output the sampled color.
+	out_fragColor = color;
+}