Dota 2 – How Big is the Area That Prevents Neutral Creep Spawns?

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It is a known fact that putting wards inside the neutral spawn camps prevents them from spawning but recently, I see our neutrals camps not spawning any creeps.
I checked the replay and saw that the opposing team put the ward behind the neutral camp instead of the usual in-front.

This is new to me so now I ask how big is the radius(or area) that the game checks? I always thought is was a triangular area in front of the neutral camp.

EDIT:
If the vision of the neutrals camps prevents them from spawning, then how come this ward does not prevent them from respawning?
neutral camp respawned

Best Answer

Here are the spawn boxes for the radiant side of the map courtesy of http://dota-2.co/topic/4159-neutral-camp-spawn-points/:

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