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From HalfLife 2 Knowledge Base

Are you sure of your point-based entity definition? A weapon is not a brush-based entity but it has a volume. I'm a bit confused.

They speak about three categories : http://www.valve-erc.com/srcsdk/Code/MyFirstEntity.htm

Machiavel

You make a good point. I remember the documentation mentioning three basic types in some places, and only two in others. I think that it somewhat depends on how you look at it. You are right that weapons are entities in Hammer and that by my definition, are entities proper. I will update the article. Thanks. =)

I have now updated the article. I'm starting to think, thought, that the definition of "types" of entities depends on how you look at the issue. If you're thinking in terms of how Hammer treats entities, you may have one set of types that you recognize; if you think in terms of how Source treats entities, you may well have another. I'd very much welcome discussion of this issue here, and I'll be sure to keep the article up-to-date on the general consensus of opinion on this. That's what makes Wiki's so great. ;)

I reread your definition several times and I find it is really more accurate. I think however a fourth definition can be added : the logical entity definition. According to the SDK documentation, a logical entity is an entity that :

[...] have no position in the world, no visual component, and only exist to service input from the game map and make decisions based on the state of the world. Logical entities do not move and they do not have a model, they simply receive inputs and send outputs depending on their exact utility. An example would be a logic_counter entity that stores a value that can be added to or subtracted from. Other entities in the map can access the entity via inputs or get information from it via outputs. The entity’s position is irrelevant in this case, which is the major factor in declaring an entity logical.

Why to add this? To sort the entities according to their spatial component.

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