Evasion



Evasion ( $$e$$ ) is mechanic that allows the unit to dodge an incoming attack. When evaded, the attack gets completely nullified. This means, anything that relies on attacks to hit their targets do not trigger, which includes most attack modifiers, and on-hit effects.

Mechanics
Evasion and blind trigger upon landing an attack, which is on projectile impact for ranged units. If it triggers, the attack does not affect the evading unit at all, so that no on-attack effects are triggered.

A similar mechanic to evasion is blind. While evasion makes a unit evade incoming attacks from other units, blind makes a unit miss upon attacking other units. Just like evasion, when an attack misses to blindness, it gets completely nullified.

True Strike and Accuracy are mechanics that nullifies Evasion.

Visual Feedback
Upon missing an attack on an enemy, a red floating text appears, reading, visible to the attacking player only. The enemy, who was just missed by an attack, also sees a floating text, but in white and reading  instead. Furthermore, a missed attack does not play any of the attack impact sounds.

Uphill Miss Chance
The uphill miss chance is a conditional effect, that only affects ranged attack projectiles of non-flying units. It causes 25% of the ranged attacks to miss if the attacker is at a lower terrain level as the target. A unit is considered to be on higher elevated terrain when it is no longer visible to the player due to the terrain. This means when an enemy stands on a ramp, but is still visible to the player, there is no uphill miss chance, but as soon as they disappear in the fog by moving the ramp further up, uphill miss chance applies. It does not matter how many terrain levels difference is between them, the miss chance always stays 25%.

Melee units, and flying units cannot miss due to the terrain.

Uphill Miss Chance Multiplier ( $$e_{up}$$ ) is defined as



Just like evasion and blind, uphill miss chance triggers upon the attack landing (which is on projectile impact for ranged heroes), not upon finishing the attack (which would be upon projectile launch for ranged heroes). This means moving up onto an elevated area after an attack projectile has been launched may cause the projectile to miss on impact to uphill miss chance, even when both units were on the same ground level as the projectile was launched.

Total Evasion
There are two main components in evasion:
 * Evade Chance - also known as Miss Chance, the chance for attacks to miss and nullify the attack.
 * Accuracy - the hit chance for attacks to hit and damage the unit.

Calculating the total Evade Chance of a unit involves using Evasion Sources, Blind Debuff Multiplier and the Uphill Miss Chance.

Stacking
Multiple sources of evasion stack multiplicatively with each other, while sources of blind effects stack additively with each other and multiplicatively with evasion. The uphill miss chance stacks multiplicatively with evasion and blind. While the actual chance to evade is diminishing, each source of evasion increases effective HP against physical attacks more than the last due to evasion's exponential nature. The chances of all sources of evasion and blind are determined by pseudo-random distribution.

Evade Chance ( $$P(e)$$ ) and Final Evasion Chance ( $$\sum e$$ ) is defined as
 * $$P(e) = 1 - \prod_{i=1}^n (1-e_{i}) \times e_{bMu} \times e_{up}$$


 * $$\sum e = P(e) \times \sum ac$$

With  being the Evasion Sources,   the Blind Debuff Multiplier and   the Uphill Miss Chance.

Accuracy ( $$ac$$ ) and Final Hit Chance ( $$\sum ac$$ ) is defined as


 * $$P(ac) = 1 - \prod_{i=1}^n (1-ac_{i})$$


 * $$\sum ac = 1 - \sum e \times \big(1 - P(ac)\big)$$

With  being the Accuracy Sources.

Examples
E.g. for Butterfly the chance to get hit is % because Butterfly has % evasion. The source of evasion values must be expressed in hundredths (so if we have 50% evasion, the value needs to be 50/100 = 0.50).
 * Example 1

As an example, if Phantom Assassin has Level 4 Blur ( chance to get hit) and Butterfly ( chance to get hit), her chance to get hit by attacks is *  =  or %. A more concrete way of thinking about evasion stacking is that for an attack to bypass an evasion stack and connect, it should bypass each source of evasion in sequence. Only if all sources of evasion fail, is the attack able to deal damage.

Blind
Blind is a debuff that makes a unit miss upon attacking other units and sources of blind effects stack additively with each other.

Blind Debuff Multiplier is defined as


 * $$e_{bMu} = 1 - \sum \text{min} (e_{b})$$

With  being the sources of Blind.

The following abilities are the sources of blind:

True Strike
True Strike prevents the unit's attacks from missing, negating evasion, blindness and the 25% uphill miss chance for ranged units. It also prevents melee attacks from missing when the target moves more than 350 range away before the attack. Although unable to miss, attack projectiles of a ranged units with True Strike can still be disjointed. True Strike does not work when attacking buildings. However, it works against any other unit, including wards and allied units.

Accuracy
Accuracy may refer to two different things:
 * It may refer to true strike's counterpart. While True Strike prevents the unit to miss any of its attacks, accuracy prevents the units from being missed by any attack.
 * It also may either refer to chance-based true strike, where attacks gain a chance to ignore evasion and blind effects.

Sources of Accuracy by first definition

Sources of Accuracy by second definition