Basil Item Design
A thing that is created and managed within Basil is called an “item”. An item can be most anything from a mesh representation to a UI element to a camera view.
Items are just identified containers that can be anything: meshes, animations, cameras. To the container, functionality is added as “able”`s. That is, a mesh item can be positionable, or animatable, or whatever-able.
This is a riff on the entity/component model found in many game engines.
Access to the item’s functionality and the functionality of the “able”s for the item is through “properties” which are simple name/value pairs. Each “able” adds some properties to the item and the item is discovered and operated on by reading and changing the values of the properties.
Every item is an instance of BItem which provides the base properties,
item collection management, and the “able” addition, removal, and management.
The base properties are:
| Property | Gettable | Settable | Desc |
|---|---|---|---|
| _Type | yes | no | One of ?? |
| _Id | yes | no | Unique string identifier for this BItem |
| _OwnerId | yes | no | Connection/service that created this BItem |
| _State | yes | no | One of “UNINITIALIZED”, “LOADING”, “FAILED”, “READY”, “SHUTDOWN” |
| _Layer | yes | no | String name of group this BItem belongs to |
| _Unique | yes | no | A unique item key supplied by the creator or generated if not |
ABLEs
Displayable
This defines a displayable item. It usually is a MeshSet.
| Property | Gettable | Settable | Desc |
|---|---|---|---|
| DType | yes | no | One of ?? |
| AABB | yes | no | axis aligned bounding box as “x,y,z,x,y,z” |
Other properties depend on the value of “_DisplayableType”:
MeshSet
| URL | yes | no | URL needed for loader |
| LoaderType | yes | no | One of “GLTF”, ?? |
| AssetAuth | yes | yes | token to use for fetching the asset |
Instanceable
This ability represents an instance of a displayable in the 3d space. Often, there is a Displayable and Instanceable on a single item – the case where there is a single instance of the displayable asset in the 3d space. There could be a single Displayable item with many Instancable items that reference that displayable. In this latter case, there will not be Displayable properties in this item but, instead, a “DisplayableRef” property will be present.
| Property | Gettable | Settable | Desc |
|---|---|---|---|
| Pos | yes | yes | Position as “x,y,z” |
| Rot | yes | yes | Rotation as “x,y,z,w” |
| PosCoord | yes | yes | Coordinate system code for “Position” |
| RotCoord | yes | yes | Coordinate system code for “Rotation” |
| DisplayRef | yes | no | ID of item with Displayability if not present here |