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Runtime, collision, events, presets, scenarios

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Rebuilding in game

  • UpdateAfterChangeAnyProperty() (BlueprintCallable) — call after changing any of the structure's properties at runtime. Works only if Mobility ≠ Static. It aligns the points, rebuilds the geometry, respawns the additional actors and rebinds the hit events.
  • Mobility (EComponentMobility) — mobility of every generated component. Affects lighting and whether components take part in baking. For a runtime rebuild set Movable or Stationary. A generated component is never left more static than Root Mobility — set that to Movable and the meshes follow.
  • Root Mobility (EComponentMobility, default Static) — mobility of the actor's own spline root. Leave Static for baked lighting and the pre-7.x behaviour. Set Movable to attach a movement component (e.g. Rotating Movement) or to move / rotate the whole actor at runtime — set Mobility to Movable too so the generated meshes move with it.
  • SplineComponent — read-only from Blueprint.

The Stats section (read-only)

Refreshed after every build, never saved into the level:

Field What it shows
Instanced Mesh Components how many InstancedStaticMeshComponents the last build produced (one per unique mesh in Line mode).
Total Instances how many mesh instances sit across all those components.
Spline Mesh Components how many SplineMeshComponents (one per element per span in Curve mode — climbs fast).
Polygon Components how many procedural meshes the polygons produced.

Collision (FSCCollisionSettings)

The Collision section on the actor. The settings apply uniformly to every generated component — instanced meshes, spline meshes and polygons alike.

Parameter Purpose
Override Collision turn collision control on. While off, the legacy behaviour is kept: ISM components stay at the engine default and Spline Mesh components are forced to Query Only.
Collision Profile the collision profile for every component.
Generate Hit Events needed for the OnSplineCraft…HitEvent delegates to fire at all. Also needs a profile with physics collision, such as BlockAll.
Generate Overlap Events generate overlap events.
Polygons Create Collision build collision geometry for polygons. Turn it off for purely decorative shapes.

Instanced components are keyed by "mesh + materials", so one component is shared by posts / sections / tubes / knobs that use the same mesh. That is why the collision settings are global to the actor — they cannot be split per element type without splitting the ISM.

Hit events

FSplineCraftStaticMeshHitDelegate (BlueprintAssignable), bound in BeginPlay:

  • OnSplineCraftSectionHitEvent
  • OnSplineCraftTubeHitEvent
  • OnSplineCraftPostHitEvent
  • OnSplineCraftKnobHitEvent

Parameters: Sender, HitComponent, OtherActor, OtherComp, NormalImpulse, Hit.

For the events to fire: Override Collision on, Generate Hit Events on, and a collision profile with physics blocking (BlockAll or similar).

Presets (USplineCraftPreset)

A style-container asset. The Preset field on the actor and two editor buttons:

  • Apply Preset — load the style onto the actor.
  • Save To Preset — store the actor's current settings into the asset.

A preset carries: Mode, Visible Last Point Elements, Posts, Tubes, Sections, Knobs, Free Knobs, Polygons, Collision, Use Random Seed / Random Seed, Mobility.

A preset does not touch what belongs to one particular actor: the spline shape, the alignment tools, Spline Close Loop, Openings and Design Notes.

Create one: Content Browser → right click → Miscellaneous → Data Asset → class SplineCraftPreset. Ready-made samples are in Content/Samples.

Build Scenario — building step by step

The SplineCraft Build Scenario asset (USplineCraftBuildScenario) is an ordered, timed sequence of presets. An actor with a scenario assigned becomes a director: it shows none of its own geometry, and spawns one child SplineCraft actor per step — along its own spline, with the step's offset. So one preset raised on Z becomes the floors of a building. Reverse is the same sequence taking the structure back down.

Actor settings (the Build Scenario section)

Parameter Purpose
Build Scenario reference to the scenario asset. Empty — the actor behaves normally.
Play On Begin Play start the scenario automatically when the game begins.
Preview Progress editor only, 0→1: scrub to see the build with no timers. 0 clears the preview.

Methods (Blueprint)

Method Effect
Play Build Scenario (bReverse) start / restart. false builds up, true takes a finished structure back down.
Stop Build Scenario stop and remove every step it has spawned.
Finish Build Scenario Now settle at the end state at once.
Is Playing Build Scenario whether the scenario is running.

Events

  • On Build Scenario Step Shown (StepIndex, Label) — a step appeared.
  • On Build Scenario Finished — the sequence finished.

The scenario asset

USplineCraftBuildScenario: Description, Start Delay (s), Loop (+ Loop Restart Delay, forward playback only), Steps.

Step (FSCBuildStep): Label, Preset, Delay Before Show (s), Offset (FTransform relative to the director — raise it on Z for floors), Appear Mode, Appear Duration (s), Rise Distance (cm).

Appear modes (ESCScenarioAppearMode): Instant, Rise From Below (rises from Rise Distance below its place), Scale Up (grows from nothing), Material Progress (drives a scalar parameter SplineCraftBuildProgress from 0 to 1 on the step's materials — works only if the material reads that parameter).

The step child actors are Transient (never saved into the level) and forced Movable. It is fully additive: without a scenario assigned the actor's behaviour is unchanged.

See also