44 lines
1.8 KiB
Markdown
44 lines
1.8 KiB
Markdown
*| [JavaECS](../../README.md) | [docs](../overview.md) | entity*
|
|
# Entity
|
|
|
|
### Contents
|
|
[About](#About)
|
|
|
|
[Usage](#Usage)
|
|
|
|
[Notes](#Notes)
|
|
|
|
## About
|
|
An 'entity' is a unique ID.
|
|
|
|
For most implementations, it makes sense to use a simple integer value - usually in a packed array (*reuses the most minimal value it can*)
|
|
|
|
E.g.: The ID 101 would be the next selected value for a new entity.
|
|
|
|
>100 | 101 | 102| 103| 104| ...|
|
|
>:----:|:-----:|:----:|:----:|:----:|:----|
|
|
><span style="color:gray">used|unused|<span style="color:gray">used|<span style="color:gray">used| unused| <span style="color:gray">....
|
|
<br>
|
|
|
|
**This ID represents a specific instance of a game object**
|
|
|
|
e.g. character, vehicle, effect etc.
|
|
|
|
___An entity contains no further data.___
|
|
|
|
In order to be useful, its identifier must be registered to one or more [components](../component/component.md).
|
|
|
|
|
|
Entities are also initialised with a Java [BitSet](). Each bit represents the index of a component, to determine which component an entity is registered to
|
|
|
|
## Usage
|
|
*some specific usage info here*
|
|
``` java
|
|
void todo();
|
|
```
|
|
|
|
## Notes
|
|
* The only requirement for a Entity is that it has a unique ID. An [entity manager](../manager/entity_manager.md) could implement a more complex ID system such as using a packed array for only a small region of IDs, or using named IDs by use of a dictionary or ordered hash-map
|
|
* The maximum number of entities is limited by the size of the container used to store it. E.g., for a 32-bit unsigned integer, there are ~4.3 billion ID's available. But keep in mind that such a large amount of IDs will take significant time for each system to consider.
|
|
* LinkedList is used to initialise the arrays, as a linked list is not limited to a maximum size: (https://stackoverflow.com/questions/3767979/how-much-data-can-a-list-can-hold-at-the-maximum)
|