Spawning & Waves

ASKScrollSpawner · ASKWaveDirector

ShmupKit has two ways to get enemies into a level, and they are meant to be mixed freely in the same stage. They share one spawn path, so an enemy configured by either arrives identically.

System	Triggered by	Best for
Placement	Position — the terrain scrolling to a marker you dropped in the level	Terrain-tied units like turrets on an island, and hand-placed set pieces
Waves	Time — a global clock running down a list of steps	Timed formations, endless streams, scripted attack sequences

Placement spawning

Drop a BP_ScrollSpawner into the level and add spawn points to it. The spawner attaches itself to the scrolling background on play, so its points ride in with the terrain — which is what makes position mean timing.

The spawner

Property	Default	Purpose
Attach To Terrain	On	The default for its points: ground units ride the island, air units fly free. Each point can override it.
Spawn Lead Distance	200	Units above the top edge at which enemies are created, so they scroll into view rather than popping in.
Add Spawn Point	—	A button in the Details panel that adds a point in one click.

A spawner needs a camera director and a scrolling background in the level, and warns if either is missing. Set the root Billboard's sprite to give it a recognisable icon in the viewport.

Spawn points

Each point is one enemy or one formation. Add several under a spawner and drag them into place.

Property	Purpose
Enemy Class	Required. What to spawn.
Formation	Optional. Spawns a whole group in a shape instead of a single enemy.
Path	Optional. The route the spawned enemies fly.
Mirror Path	Flips that route horizontally, so one authored path serves both sides.
Group Tag	Points sharing a tag all fire together when the leading one crosses the line, so an authored spread survives instead of trickling in.
Entry Depth	Spawn this far below the top screen edge, anchored to the camera rather than the marker. 0 uses the marker's own position.
Attach To Terrain	Per-point override: use the spawner's default, force attach, or force free flight.

Per-point overrides

Retune one placement without duplicating the enemy asset. Every override follows the same rule: 0 or None keeps the enemy's own value.

Override	Replaces
Move Speed Override	The enemy's movement speed.
Health Override	Its max health, for this spawn only.
Score Value Override	Points awarded on death.
Weapon Data Override	The weapon fitted to its front mount.
Drop Table Override	What it drops.

Three rules that matter

Editor visuals

Each spawn point draws a preview mesh of the enemy it will spawn, a facing arrow, and a floating label estimating how many seconds until it reaches the screen — so a level's pacing is readable in the viewport without pressing Play.

Wave spawning

Place an SKWaveDirector in the level and give it a list of wave assets. It runs them in order on a clock.

Property	Default	Purpose
Waves	—	The wave assets to run, in order.
Auto Start	On	Begin on play. Turn it off to trigger waves yourself.
Loop	Off	Restart from the first wave after the last completes — an endless mode in one tick box.

Function / Event	Purpose
Start Waves / Stop Waves	Manual control.
Jump To Wave / Jump To Step	Skip directly to a point in the sequence. Useful for testing.
On Wave Started	Fires with the wave index.
On Wave Cleared	Fires when every enemy from a wave is gone.
On All Waves Complete	Fires at the end of the list — a natural place to spawn the boss.

Wave assets

A wave defines what to spawn, then lists the steps that spawn it.

Property	Purpose
Enemy Class	What this wave spawns.
Formation	Optional group shape for each step.
Path Override	Route for the spawned enemies.
Weapon Data Override / Drop Table Override	Wave-wide retuning, same 0-or-None rule as spawn points.
Steps	The spawn events that make up the wave.
Wait For Clear	On by default: the next wave waits until this one is wiped out. Off runs waves on the clock alone, overlapping them.
Post Wave Delay	Seconds of breathing room after the wave ends.
Pre Warm Pool	Creates the wave's actors up front, so a big first wave doesn't hitch as it spawns.

Steps

Property	Purpose
Delay	Seconds to wait after the previous step before this one fires. It is relative, not an absolute timestamp — so inserting a step shifts everything after it rather than requiring a rewrite.
Spawn Origin	Where this step spawns, in world space.
Spawn Facing Yaw	Which way the spawned enemies face.
Mirror Path	Flips the route for this step only, so alternating steps sweep in from opposite sides.
Move Speed / Health / Score Value Override	Per-step retuning.

Formations

A formation spawns a group as one unit. Both spawn points and wave steps accept one.

Type	Behaviour
Points	A fixed shape. Each member has its own offset, an optional fire delay so the group doesn't volley in perfect unison, and an index used for per-member drops.
Trail	Follow the leader — Trail Count members spaced Trail Spacing apart along the path.

Property	Purpose
Members	Points mode. Each entry is an offset, a fire delay and an index.
Member Spawn Delay	Points mode. Staggers the members' arrival instead of popping the whole shape in at once.
Trail Count / Trail Spacing	Trail mode. How many follow, and how far apart.
Drop Table	Applies to every member.
First Drop / Last Drop	Trail mode. Give the leader or the straggler a different reward — the classic "kill the whole snake" bonus.

Paths

A path is a list of waypoints an enemy flies. Assign one to a spawn point, a wave, or directly to an enemy's movement component with the Follow Path mode.

Property	Default	Purpose
Waypoints	—	The route, in order.
Move Speed	0	Speed along the path. 0 uses the enemy's own speed.
Speed Curve	—	Optional curve scaling speed along the route, for a swoop that accelerates through the middle.
Smooth	On	Curves the route through the waypoints instead of turning sharp corners.
Orient To Path	On	Points the enemy along its direction of travel.
Rotate To Entry Direction	Off	Faces the enemy along the path's opening direction as it spawns.

Authoring paths visually

Place an SKSplinePath actor, shape the spline in the viewport, and press Bake To Path Data to write it into a path asset. Point Spacing controls how finely the curve is sampled, and Load From Path Data brings an existing asset back onto the spline for editing.

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