Entities give life to your level. They are the monsters, doors, switches and lights that turn your static architecture into an interactive environment. Careful use of entities is critical to creating an interesting, unique and fun level for others to play.
Unlike solids, entities are not created within Worldcraft. Most users will simply choose from a pre-existing set of entities provided with Half-Life. Once you have selected the appropriate entity, Worldcraft gives you control over its placement and other properties.
There are two types of entities: point-based and brush-based.
Point-based entities exist only at a certain exact point. Examples include lights, monsters, and player start points. (Monsters do have an area, but it is defined by the game code and is not modifiable from within the map.) Some point type entities are just that: points. For example, the env_beam entity, which controls Half-Life's beam effects, uses two info_target entities as targets and the beam of light runs between these two points.
Brush-based entities are entities that depend on either a brush for their physical presence (like doors, trains, and other moving entities) or an "area" (like triggers, which require an activation field).
Point-based entity placement
Placement of point entities is simple:
Press Shift+E to go into entity mode..
Note: the entity list in the New Objects dialog is for point-based entities only. For information on brush-based entities, please refer to the following section.
Click in a 2D window, then position the entity cursor with the mouse.
Tip: You will most likely need to edit the entity properties after you place a point-based entity. Select the entity and press Alt-Enter to view the entities properties dialog box. This dialog pops up automatically for brush-based entities.
Brush-based entity placement
Brush-based entities are a bit more complicated than point-based entities, but should not pose any difficulties once you know their basics.
Create the object where you would
like it. You can use as many brushes as you'd like when building a
Tip: Bring up the entity properties for a brush-based entity the same way you do for a point-based entity: select it and press Alt-Enter.
You will notice that brush-based entities appear as a different color in the 2D windows, typically purple.