Trigger Loop
Terminology
Usually, when a 'trigger projectile' (one with a Trigger or Timer) hits an entity it releases the payload it is carrying and then dies. Projectiles which Pierce (either naturally, or via the modification of Piercing Shot) do not die on impact, and can release a payload multiple times while in contact with the same entity. Projectiles that Penetrate entities can only hit a given entity once, but also do not die on impact, and so remain able to hit other entities (once each) as well.
If the trigger projectile's payload contains a projectile which the trigger projectile can hit, a loop can be created. This costs nothing beyond the initial cost of the spells used to create it, but can produce hundreds of copies of the payload - autonomously over time - for free. This obviously has huge destructive potential, but also enables the creation of some very useful wands for things like automated farming of wands/hearts.
Basic Theory
- Projectiles can have (or be given) a trigger, which has a payload which is released...
...upon collision with terrain, or entities (this can happen multiple times).
...upon collision with terrain, or entities (this can happen multiple times), and/or once after the timer duration elapses.
...when the trigger projectile expires (never more than once).
- Most projectiles die on impact, those that don't are said to have the property of either Piercing or Penetrating
- Piercing projectiles can hit multiple times on multiple entities.
- Penetrating projectiles can hit multiple entities, but only exactly once on each.
- Some projectiles are also entities, and some of those can be hit by other projectiles.
- Some projectiles (those that have Friendly Fire enabled) can hit and cause damage to entities aligned with your faction, including your projectiles.
So if you have a friendly-fire projectile with a Timer or Trigger (Projectile A), and a projectile that is an entity that can be hit (Projectile B), you can fire A at B, and trigger A's payload release.
If A is piercing, or penetrating, then it can hit multiple Bs before dying, releasing the payload each time.
If A's payload contains B, then A releases B (and anything else in the payload) every time A hits B, creating a loop.
Piercing Trigger payload
While not a loop, this is a very powerful and simple technique.
If you either:
- add Piercing Shot to a "with Trigger" or "with Timer" spell (like Spark Bolt With Trigger)
- add Add Trigger to a spell which has Piercing built-in,
then you can create multiple copies of the payload by simply shooting an enemy with the projectile.
Shuffle
Spells/Cast
Cast delay
Rechrg. Time
Mana max
Mana chg. Spd
Capacity
Spread
Speed
Shuffle Spells/Cast Cast delay Rechrg. Time Mana max Mana chg. Spd Capacity Spread Speed
Creating a loop
By adding a spell to the payload which can itself be hit by the trigger projectile, a closed loop is created. The reliability of this effect depends on the interaction between the release of the hittable projectile and the trajectory of the trigger projectile, and can be improved by adjusting the timings involved.
The most basic form of this is not self-starting, i.e. it needs to hit an entity to begin the loop.
Self-starting loop
The loop effect only begins when the trigger projectile hits for the first time. By releasing it together with an entity to hit (e.g. another Pollen) you can make the loop begin immediately.
A two cast wrapping setup can be used on a budget. This only uses 1 pollen spell and does not need a spacing spell, but it does require two separate casts.
Pinpoint of Light works especially well, but can be replaced with other piercing/penetrating projectiles:
The Long-Distance Cast adds spacing to prevent the spark bolt from hitting the pollen on the first frame before piercing applies. A Luminous Drill Timer also works well for this.
A two cast wrapping setup can be used on a budget. This only uses 1 pollen spell and does not need a spacing spell, but it does require two separate casts.
More spells can then be added to the trigger to make, for example, a travel wand:
Exponential loops
If one loop creates a single new hittable projectile, it is self-sustaining and will continue until the trigger projectile expires.
If one loop creates more than one hittable projectile, it has positive growth, and can potentially spawn new projectiles exponentially. This can be very laggy, and often leads to runaway looping that crashes the game.
Tick Rate, Timing & Delays
The speed at which payload release (and looping) happens depends on the 'tick rate' of the trigger projectile. Some projectiles do damage every frame (typically 60 times a second), others less frequently. The higher the tick rate, the higher the potential damage output. This is set via the ProjectileComponent value damage_every_x_frames, and defaults to 1.
Nested loops
One Pollen loop can be used to trigger another. This very quickly produces a lot of spell copies. It is quite easy to crash the game this way
Note: It is impossible to duplicate the trigger chain more than once (using Wand Refresh) so the degree of nesting is limited by available wand space.
When using wands with high spells/cast (e.g. Multitudes) you can use this combo on the end of the wand to ensure it cannot wrap, and thus cannot create accidental nesting:
You can also have an 'abort' wand on hand to kill the loops if they start to lag heavily. Spells To Power (or the other 'Spells To' variants) and Explosive Detonator both work for this.
Modifier Synergies
Pinpont of Light benefits from reduced projectile speed - which results in a denser payload distribution. Projectile Energy Shield is good for this - although it also limits the lifetime of the projectile. Heavy Shot is also good, albeit more risky on a Friendly Fire enabled projectile. Lifetime can also be increased, which produces more copies overall. Path modifiers (particularly Orbiting Arc) keep the loop in one place, or (particularly Spiral Arc, Chaotic Path) ensure wide area of effect coverage.
While not strictly necessary, stray pollen stragglers not destroyed by the projectile can be eliminated using Nolla. A death trigger attached to the Pollen can then spawn the payload. This introduces a 2-frame delay (due to Nolla taking one frame to be cast and one to take effect) - this can be very useful.
Lumi Drill Timer, Long Distance Cast, Delayed Spellcast (& Add Timer) etc. can all be used (optionally with Nolla or Lifetime modifiers) to adjust how the payload spells are distributed. By giving the intermediary spell an increased lifetime you can generate a large number of projectiles-in-waiting, to be released together in a devastating swarm using Explosive Detonator.
Spells to Power
Spells To Power harvests spells you have cast for their damage, and applies it to another projectile. You can use this with a trigger loop as an accumulator, the loop creates long-lived projectiles over a few seconds, all of which are then harvested by Spells To Power into a single, high damage projectile. This is usually not particularly efficient, but can look really cool.
Pollen alternatives
Some other spells can be used in the same way as Pollen to produce loops. These tend to have drawbacks compared to Pollen (e.g. they explode, or bleed, or won't sit still).
Another alternative is... shoot yourself. A projectile with Piercing/Friendly Fire enabled will happily hit you, and in doing so fire off the trigger payload as long as the projectile remains in contact - which adding Boomerang will help with. If you ensure the projectile doesn't actually cause you any damage this can be very effective.
Tentacle Synergy
Summon Tentacle is another spell with lots of weird properties. Tentacle can be used in the payload of a Pollen loop to:
- repeatedly cast spells which originate from you, or
- attach multiple copies of certain modifiers to the piercing trigger,
- ... among other things.
Summon Tentacle wisps also work great as the trigger spell to create stationary loops that don't unload with distance.
Technical Info
Penetration & Piercing - Config Flags
Penetration & piercing behaviours are controlled by two configuration flags.
penetrate_entities |
on_collision_die |
Effect | |
|---|---|---|---|
No
|
Yes
|
Can hit once | |
No
|
No
|
Piercing | Can hit multiple entities, each one multiple times |
Yes
|
Yes
|
Penetrating | Can hit multiple entities, but only once per entity |
Yes
|
No
| ||