Entity
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Entity is an object defined within 
Source usually for the purpose of being interact-able by players or by other entities via I/O system. The world itself is also an entity which is created as a combination of world brushes.
Types of entities
Entities can be separated into few different type. From the perspective of Hammer editor they can be separated based on how they are created in the editor which is determined by their FGD definition.
| By map editor | |
|---|---|
| Types | Info |
| Brush entity | A Brush Entity is created by tying an entity to a BSP geometry brush in the map, giving the brush a specific effect or ability defined by the entity tied to it. When compiled the tied brushes are turned into brush model used by this entity. |
| Point entity | Point Entities are entities created at a specific position point on the grid. Some require a model to be selected for them in order to function fully. |
| By how it's processed | |
|---|---|
| Types | Info |
| Internal entity | Internal entities are those which are processed by VBSP then either deleted or merged into another entity. They do not exist when the map is running, so they won't count to the entity limit. Internal entities get special treatment by the map compile tools and are removed from the final product, usually stored in a special chunk. |
| Semi-internal entity | Semi-internal entities are those entities which remain as entity in the map but require big chuck of their functionality being taken care of by the compiler.
For example func_areaportal brush model is moved to world by VBSP leaving the entity without any brush in a map file. Or func_detail_blocker which blocks creation of detail sprites during compile and remains in a map possibly just as an information for decompilers. Or even the light related entities which require VRAD to do its job. |
| Non-Internal entity | non-internal entities are not processed by VBSP and remains as a separate entity. These are typically interactive objects or characters that the player can interact with or that affect gameplay. |
| General separation from the game's perspective based on intended use | |
|---|---|
| Types | Info |
| Brush entity | Entities that use a brush model. |
| Model entity | Entities that use a studio model. For example prop_physics, prop_dynamic, player, npc_alyx. (all of these are subclasses of CBaseAnimating as that's the only class by default that's meant to draw studio models) |
| Point entity | Entities whose position is relevant for its functionality and don't use 3D model, most often no visual representation with exception of particles, sprites, decals. For example info_target, env_sprite, infodecal, info_particle_system (usually derived from CPointEntity but it's not the rule) |
| Logical entity | Entities whose position is irrelevant to its functionality. For example logic_auto, logic_relay, math_counter, info_director (often derived from CLogicalEntity but it's not the rule as even logic_auto isn't) |
Limitations
For reasons of memory allocation, there is a limit to the number of entities Source can manage at once.
The combined size (in bytes) of a map's entity data should also be considered, even if the number of entities is within safe limits. Large amounts of entdata can take a noticeably long time to transmit from server to client, and may lead to crashes.
See also
- Category:Entities
- Adding Point Entities (part of a series of tutorials)
- Creating Brush Entities (ditto)
- Entity creation (a quick reference)
- Entities in Depth
- List of entities
- Coding Your First Entity
- Console command dump_entity_sizes
- preserved entity