Vision

Vision (or Sight) is an attribute of units and Structures that allows players on the same team to see enemy units or Structures, or to see things through the Fog of War. Vision is required to be able to target enemies with Basic Attacks and unit targeted Abilities.

Gameplay

Fog of War

The Fog of War is the game mechanic in which a player's access to information is limited to the region of map which is currently revealed by his units, buildings, and abilities. It is represented by dark and light regions on both the minimap and the main screen. As a teams units move about the map they grant full vision to the team within the vision range of that unit. This is shown on the minimap as a fully lit region. When a team loses sight of an area, either by a unit moving away or dying, the map area reverts to a darker shade and any information about units is removed from the main screen and the minimap.

Sight

Most units (Hero, Minion, Summons allied Monsters and Mercenaries or Structure) have sight, allowing them to provide ground vision in a certain radius around them, measured from the unit's center. Enemy units are also in most cases tested for vision from their center meaning that vision is unaffected by the units Collision Radius. Heroes usually have a sight range of 12. There are some Abilities and effects that increase or restrict an affected unit's sight radius.

Units' sight is processed in 45 degreee sections and can be obstructed by terrain and enemy Gates and Walls. Other Structures do not block sight, nor is units sight reduced by being on the other side of a Fort, Keep, Tower or Core.

Bushes

Main article: Bush

Bushes are a gameplay element that obstruct sight into and through them for units that are not within their area.

Vision sources

Most Objectives grant vision in a small area around them, while they are active until they are captured. Some Battlegrounds also feature Watchtowers or Recon Camps, that can be captured to provide unobstructed vision in a large area around it.

Revealed status effect grants vision over the target, and reveals Stealthed and invisible enemies, as long as they are not unrevealable.

Attack and Ability interactions

In most cases, Basic Attacks and Abilities can be used to momentarily grant vision in their area or path or over the enemy units hit by them, and can be used to scout beyond terrain and bushes. Likewise, a Hero using an Basic Attack or an Ability from outside the enemies vision, can give away their position.

Below table specifies how different events generally grant vision.

Event	Attacker	Target
Damaging / being damaged a regular Basic Attack	Does not gain vision of target.	Gains vision of the attacker for 2 seconds, if they were not already visible. Subsequent instances refresh the duration.
Damaging / being damaged by an empowered Basic Attack dealing Spell Damage	Does not gain vision of target.	Gains vision of the attacker for 2 seconds, if they were not already visible. Subsequent instances refresh the duration.
Damaging / being damaged by a splashing or bouncing Basic Attack	Does not gain vision of target. Gaining vision over the area is Ability specific.	Gains vision of the attacker for 2 seconds, if they were not already visible. Subsequent instances refresh the duration.
Damaging / being damaged by an Ability dealing standard Spell Damage	Gains briefly vision of the target.	Gains briefly vision of the attacker.
Casting a projectile skillshot Ability (e.g. Healing Dart, Scatter Arrow)	Gains vision around the projectile as it travels.	Does not gain vision of the attacker.
Damaging / being damaged by a skillshot Ability	Gaining vision is Ability specific.	Gains briefly vision of the attacker.
Casting a targeted area of effect Ability (e.g. Flamestrike, Blizzard)	Gains vision in the area upon impact. Delayed Abilities may also grant vision beforehand.	Does not gain vision of the attacker.
Casting a projectile area of effect Ability (e.g. Globe of Annihilation)	Gains vision in the area upon impact. Gaining vision around the projectile as it travels is Ability specific.	Does not gain vision of the attacker.
Casting a Hero-centered area of effect Ability (e.g. Thunder Clap)	Gaining vision is Ability specific.	Does not gain vision of the attacker.
Damaging / being damaged by an area of effect Ability	Gaining vision is Ability specific.	Gains briefly vision of the attacker.
Damaging / being damaged by a persistent area of effect ability (e.g. Cataclysm, Black Pool)	Ability grants vision in its area. Gaining vision upon dealing damage is Ability specific.	Gaining vision is Ability specific.
Applying a Damage over Time effect	Gains briefly vision of the target.	Gains briefly vision of the attacker.
Damaging / being damaged by a Damage over Time effect	Does not gain vision of the target.	Does not gain vision of the attacker.
Damaging / being damaged by periodic aura effect (e.g. Burning Rage)	Gains briefly vision of the target.	Gains briefly vision of the attacker.
Damaging / being damaged by a "set and forget" ability (e.g. Toxic Nest, Steel Trap)	Gains briefly vision of the target.	Does not gain vision of the attacker.
Damaging / being damaged by a "set and activate" ability (e.g. Blood Rage, Concussion Mine)	Does not gain vision of the target.	Gains briefly vision of the attacker.
Damaging / being damaged by a "global" ability (e.g. Eye of Horus, Suppression Pulse)	Gaining vision is Ability specific.	Gaining vision is Ability specific.
Damaging / being damaged by an enemy Summon	Does not gain vision of the target.	Gains vision of the unit that dealt the damage. (Note: Summon that seemingly dealt the damage, may not necessarily be the origin of the damage.)
A unit summoned by you is damaged by an enemy	-	Gains vision of the attacker, if they otherwise would.
You are killed	-	Gains vision of units in radius of 3.0 upon death.