Projectile

Projectiles are entities which are produced by a spell or ranged attack which travel independently of their creator until they collide with an enemy or obstacle or reach their travel distance limit of 150 Units. Skills gems that create projectiles usually have the Projectile or Bow gem tag.

Speed and duration
All projectiles have a speed, which can be altered by modifiers. All projectiles also have a duration (which can be infinite), although in most cases this duration is not mentioned anywhere and cannot be modified, unless explicitly stated such as with the skill.

The speed and duration combined determine the distance the projectile will travel, up to its maximum range. This is important when considering projectiles that have a limited lifetime.

For example, creates projectiles which deal full damage initially, but deal less and less damage the longer they are alive. Increasing the of Freezing Pulse will cause the projectiles to arrive at the target sooner, and therefore they will deal more damage than a slower-moving Freezing Pulse that traveled the same distance.

Increasing the of limited duration projectiles will allow them to travel a further distance before they expire.

However, there are effects that occur based on the projectile's total distance traveled since launched. For instance:
 * will always arm (change into its second form) at a certain distance from its launching point, regardless of its speed
 * The damage modifiers from Point Blank and are based the projectile's total distance traveled, not how long the projectile has been alive. Note that, in the case of  or other "Projectiles Return" mechanics, the total distance traveled may be greater than the current distance from the player.

Ground and airborne projectiles
Most projectiles fly through the air, however there are some that travel along the ground.

Airborne projectiles can be aimed up and down cliffs and other height transitions, and can impact with the ground or ceiling. This can sometimes make them difficult to aim when dealing with a steep vertical angle, as they might fly over the heads of enemies or harmlessly impact the ground at the enemy's feet. Airborne projectiles will pass through most low obstacles such as small chests and rocks.

Projectiles that travel along the ground are subject to the same restrictions as a walking player. This means they cannot be fired up or down height transitions, and will instead collide with the edge. They will never impact with the ground or ceiling, but they are much more likely to be obstructed by small obstacles around the environment. Skills that create earthbound projectiles include,.

Death
When a projectile collides with an enemy or obstacle, it explodes and is destroyed. This happens even if the projectile is the result of an attack that is evaded or dodged. Intuitively a projectile that is evaded or dodged would continue along its trajectory, but that is not the case in Path of Exile.

Subprojectiles
Normally a projectile attempts to hit the first enemy it encounters, explodes if the projectile has an explosion effect, and disappears. However, some effects change the projectile hit behavior.

Effect types
At most one effect may be applied per hit. The effects are listed in order of priority.

Split
Upon hit the projectile splits into number of auto-targeting projectiles. The auto-targeting radius limitations are similar to chain.

Split arrows are considered the same arrow after splitting and therefore will not target the same monster twice. This means that in most situations split will not increase your single target hits. (see explosive projectiles for exception)

Sources of split include:

Pierce
The projectile passes through the enemy and continues along its previous trajectory. Once a projectile has exhausted its pierce count, one of the other effects listed in this section may apply.

Fork
The projectile splits into two identical projectiles which each travel at a 60 degree angle from the projectile's original path. A projectile can only fork once.

Sources of fork include:
 * (For spell projectiles when worn in the left ring slot)
 * (For spell projectiles when worn in the left ring slot)
 * (For spell projectiles when worn in the left ring slot)

Chain
The projectile chooses a target within a certain radius, and travels in the direction of that target. A target cannot be hit twice by the same projectile. If a skill produces multiple projectiles at once and chains, none of the projectiles may chain to an enemy which has already been struck by a projectile from the same attack or cast. If there are no valid targets in range of the original enemy, it will target an enemy but not hit, instead passing through. Chain has a specified number of iterations.

Sources of chain include:
 * (For attack projectiles when in main hand)
 * Ricochet passive for the Deadeye ascendancy.
 * (For spell projectiles when worn in the right ring slot)
 * (While at maximum frenzy charges)
 * Ricochet passive for the Deadeye ascendancy.
 * (For spell projectiles when worn in the right ring slot)
 * (While at maximum frenzy charges)
 * (While at maximum frenzy charges)

Also,, , , , , , and can chain despite not being projectile skills.

Return
The projectile returns to the original firer. Targets can be hit once on the way out and once on the way back, however, the specific target they return from is only hit once. Its priority is after pierce/fork/chain.

Sources of returning projectiles include:
 * skill
 * Vengeant Cascade passive (for attack projectiles)
 * (Descent: Champions-exclusive)

Explosions
Some projectiles explode on every hit, while other projectiles only explode when they disappear, dealing only normal, non-area damage on non-exploding hits.

The following skills explode on every hit:

Furthermore, all single-target on-hit effects apply on every hit.

The following skills only explode when the projectile is destroyed:

Imagine a that has, , and , and has been launched towards a pack of enemies:
 * 1) It hits the first enemy and succeeds its piercing check. The enemy is damaged and the projectile continues on its course.
 * 2) It hits a second enemy and this times fails to pierce. It forks, and there are now two projectiles which fly in different directions.
 * 3) *The first projectile
 * The first projectile hits an enemy, and succeeds its piercing check, and continues on.
 * There are no more enemies in its flight path, and it flies into a wall and explodes.
 * 1) *The second projectile
 * The second projectile hits an enemy but fails its piercing check. Since it is the descendant of a projectile that forked, it cannot fork. The projectile and none of its ancestors have chained yet, so it can still chain two times. It chains and flies backwards towards the previous enemy.
 * It hits the enemy, succeeds its piercing check, and continues on.
 * It hits another enemy and fails to pierce, but can still chain one more time. It chains towards a nearby enemy.
 * It hits the enemy and again fails to pierce. It cannot fork, and has run out of chains, so it finally explodes, dealing Fireball's area of effect damage.

Math Calculations
All calculations assume maximum possible hits in ideal situations. Several factors, for example enemies evading your attacks, will prevent max possible hits from happening.

Solo hits
Individual projectiles can only target a single monster 1 time. If you have multiple chains, they will only chain to targets that have not been hit yet.

Projectiles that fork count as the same projectile after forking. This means that fork will not increase your solo target hits per second.

Max possible individual target hits per second Formula

 * Note: This formula requires enough chains and enemies for every projectile to reach your individual target.


 * (Total number of projectiles) x (Attacks/cast per Second) = final answer.

max possible multiple target hits per second formula

 * Note: Fork is calculated as 2. Awakened fork is calculated 6.


 * Note: "Pierce on return" comes from the vengeant cascade notable.

(Total number of projectiles) X (Attacks/cast per Second) = Q

( Q ) X (Number of Pierces + 1) = Z

( Q ) X (fork or awakened fork) = T

( T ) X (Chains) = F

( T ) X ( Average number of Pierces on return) = V

Z + T + F + V = Final Answer

Explosive projectile hits
Projectiles that explode for area of effect damage on every hit will use the same formula and restrictions as above for targeting, but are capable of hitting more times against densely packed enemies.

The area of effect damage that occurs when hitting a non-targeted enemy does not prevent that enemy from being targeted by chain. This means that you can multiply your maximum number of hits for single and multiple targets by the average number of hits per explosion.

Active attack skill gems
A list of active skill gems with the gem tag: Projectile and Attack or Bow

Active spell skill gems
A list of active skill gems with the gem tag: Projectile and Spell

Support skill gems
A list of support gems with the gem tag: Projectile or Bow

Passive skills
There are passive skills that grant projectile bonuses.

Projectile damage
These passive skills grant increased projectile damage.

Projectile speed
These passive skills grant increased projectile speed.

Projectile piercing
These passive skills grant additional pierces.

Miscellany
These passive skills are related to projectiles, but do not fit into any other category.

Version history

 * Changed the behavior of projectiles. Projectile modifiers will now behave in the following order: Split, Pierce, Fork, Chain, and Return.
 * For specific mechanics that had chances to occur or not occur, you'll now be able to fall back on another behavior the projectile has. Previously if a projectile had a chain remaining, the skill couldn't return until it had chained the last time even if there were no enemies in range to chain to. Now the projectile will return, and could still make use of the remaining chain if it hits an enemy during that return.


 * Fixed an instance crash related to projectiles and Kineticism.


 * Pierce has been reworked. Items and skills that used to use or provide pierce chance now instead use or provide a number of pierces. Once a projectile has reached its pierce limit, it will not pierce further.


 * Fixed a bug where 100% pierce chance would not grant increased damage for appropriate skills.
 * Fixing an issue where projectiles did not appear to pierce on the client.
 * }