ARENA Object

ARENA objects follow the structure of Scene Message object, with general object properties, paired with a more granular detailed data sub-object which varies in form and follow the examples below.

ARENA 3D Environment is built on top of A-Frame, and it supports the majority of A-Frame’s primitives (e.g., geometries like boxes, circles, spheres) and components (that can be attached to objects, such as position, rotation, material, sound). See here for a clarification of the relation between ARENA and A-Frame properties.

Tip

In most cases, arbitrary A-Frame properties which are applied in HTML as attributes can be applied to ARENA Objects. We link the corresponding A-Frame object definition for completeness in the tables below.

Over-the-Wire Message Examples

ARENA object schemas are the basis for the over-the-wire message format. Below you can find some additional message examples and links to the respective object definitions.

Object Message

Scene Message object with a data property of the Object Data object.

{"object_id": "cube_1", "action": "create", "type": "object", "data": {"object_type": "cube", "position": {"x": 1, "y": 1, "z": -1}, "rotation": {"x": 0, "y": 0, "z": 0, "w": 1}, "scale": {"x": 1, "y": 1, "z": 1}, "color": "#FF0000"}}

Event Message

Scene Message object with a data property of the Event Data object.

{"object_id": "fallBox2", "action": "clientEvent", "type": "mousedown", "data": {"position": {"x": -0.993, "y": 0.342, "z": -1.797}, "source": "camera_8715_er"}}

Program Message

Scene Message object with a data property of the Program Data object.

{"object_id": "6aafedf3-e313-4785-a456-939de8677f07", "action": "update", "persist": true, "type": "program", "data": {"name": "wiselab/arb", "instantiate": "single", "filename": "arb.py", "filetype": "PY", "args": ["${scene}", "-b", " ${mqtth}"]}}

Scene Options Message

Scene Message object with a data property of the Scene Options Data object.

{"object_id": "e9a16478-2606-4cd0-bb9f-b03879bc8baa", "action": "update", "persist": true, "type": "scene-options", "data": {"env-presets": {"active": true, "lighting": "distant", "lightPosition": {"x": 0, "y": 1, "z": -10}, "ground": "hills", "groundTexture": "squares", "groundColor": "#444241", "groundYScale": 0.5}, "scene-options": {"jitsiServer": "jitsi1.andrew.cmu.edu", "clickableOnlyEvents": true, "privateScene": true}}}

“Scene Message” object

This is the primary payload body of every MQTT scene topic in the ARENA.

See our reference of ARENA supported objects and their properties.

Actions

The create, update, and delete actions are similar to typical C(R)UD operations.

create - Upserts an object. If the object already does exist, data fields will be merged.
update - Merges the data attributes with a currently existing object. To remove an attribute, set the value to null.
delete - Delete an object. No data field required.