RuntimePrimitiveDrawing (RuntimeDrawing) Blueprint Nodes — Usage Guide

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This document explains how to use the Blueprint-callable nodes provided by URuntimeDrawingBlueprintLibrary: what each node does, what its parameters mean, and common pitfalls.

1) Finding the nodes in Blueprints

1. Make sure the plugin/module is enabled and compiled (module name: RuntimePrimitiveDrawing).
2. In any Blueprint graph (Actor / Character / Controller / etc.):
   • Right-click empty space
   • Search for category: RuntimeDrawing
   • Nodes are named Draw... (e.g., DrawLine, DrawBox, DrawFOVSector)

All functions use meta = (WorldContext="WorldContext").
In Blueprints, the World Context is usually auto-provided from the calling Blueprint, so you typically don’t need to wire it manually.

2) Common parameter meanings (most nodes)

• WorldLocation / StartLocation / EndLocation: World-space positions.
• WorldRotation: World-space orientation (affects direction/shape orientation).
• Color (FLinearColor): Line/point color (linear color).
• Thickness (float): Line thickness.
• Depth (float): Depth priority (passed to batched line drawing).
  • Higher values often render “on top” depending on engine/render settings.
• Segment / Segments / CircleSegments: Approximation detail.
  • Higher = smoother curves, more draw cost.

3) Node reference

3.1 DrawPoint

Draws a single point in world space.

Parameters

• WorldLocation: point position
• Color
• Size (default 2)
• Depth (default 1)

Use cases

• Hit points, sample points, path markers

3.2 DrawLine

Draws a single world-space line segment.

Parameters

• StartLocation / EndLocation
• Color
• Thickness (default 2)
• Depth (default 1)

3.3 DrawLines

Draws a polyline by connecting adjacent points: Points[i] -> Points[i+1].

Parameters

• Points: array of world-space points
• PointsColor: per-point color array (must match Points length)
• Thickness / Depth

Important

• If Points.Num() != PointsColor.Num(), the function returns immediately.
• This does not auto-close. Use DrawPolygon to close.

3.4 DrawCircle

Draws a circle approximation in the XY plane (constant Z).

Parameters

• WorldLocation: center
• Radius
• Segment: number of segments (default 6)
• Color / Thickness / Depth

Notes

• The implementation generates points using (cos, sin, 0) and closes the loop.

3.5 DrawSphere

Draws a “wire sphere” using multiple circle rings along Z plus a central ring.

Parameters

• WorldLocation: center
• Radius
• Segment: affects ring resolution and ring count (clamped)
• Color / Thickness / Depth

Notes

• Ring count is Clamp(Segment, 4, 64).

3.6 DrawBox

Draws an oriented box (OBB) wireframe.

Parameters

• WorldLocation: box center
• WorldRotation: box orientation
• BoxExtent: half-size along X/Y/Z
• Color / Thickness / Depth

3.7 DrawPrisms

Draws a pyramid/cone-like prism: base polygon + lines from base vertices to the apex.

Parameters

• WorldLocation: base center
• WorldRotation
• Radius: base radius
• Height: apex height along local +Z
• NumPrisms: number of base sides (>=3 recommended)
• Color / Thickness / Depth

Notes

• Also calls DrawPolygon to draw the base outline.

3.8 DrawPolygon

Draws a polygon outline and auto-closes it.

Parameters

• Points: polygon vertices (world-space, ordered)
• Color / Thickness / Depth

Notes

• If Points.Num() < 1, it returns.
• Internally appends Points[0] to close the loop.

3.9 DrawPizza

Draws “pizza slices”: several radial lines from the center and connects outer points.

Parameters

• WorldLocation: center
• Radius
• Pieces: slice count (implementation uses Pieces - 1 radial lines)
• PerPieceDegrees: slice angle step in degrees
• Color / Thickness / Depth

Important (implementation detail)

• The outer arc connection is drawn with DrawLines(Points) without closing back to the first point.
• If you need a full outer circle, also call DrawCircle.

3.10 DrawSpline

Draws a spline as a polyline by sampling points along the spline.

Parameters

• Spline: USplineComponent*
• Color
• Segment: sample segment count (declared as float; treat it like an integer >= 2)
• Thickness / Depth

Notes

• Step is computed as: SplinePointCount / Segment.

3.11 DrawArrow

Draws an arrow: main shaft + four “wings” around the tip (Right/Up pairs).

Parameters

• StartLocation / EndLocation
• Color
• HeadLength: arrowhead wing length (clamped to arrow length)
• HeadAngleDegrees: wing angle in degrees
• Thickness / Depth

Notes

• If start/end are nearly identical, only the main line may be skipped/limited.

3.12 DrawFOVSector

Draws a 2D FOV sector in the XY plane based on WorldRotation forward direction.

Parameters

• WorldLocation: center
• WorldRotation: orientation (Forward is the sector’s center direction)
• Radius
• AngleDegrees: total angle
• Segments: arc subdivisions (min 2)
• Color / Thickness / Depth
• bDrawRays: draw the two boundary rays
• bDrawArc: draw the arc
• bDrawCenterLine: draw the center direction line

3.13 DrawFOVBoxFrustum3D

Draws a 3D camera-like frustum wireframe using near/far distances and FOV.

Parameters

• WorldLocation: origin (camera position)
• WorldRotation: frustum orientation
• NearDist / FarDist
• HorizontalFovDegrees / VerticalFovDegrees
• Color / Thickness / Depth

Notes

• Values are clamped:
  • NearDist >= 0
  • FarDist >= NearDist + 0.01
  • FOV in [0.01, 179]
• Draws 12 edges (near rect, far rect, and connectors).

3.14 DrawLatLongSphere

Draws a sphere grid made of latitude and longitude circles.

Parameters

• WorldLocation / WorldRotation
• Radius
• LatitudeLines (0..64)
• LongitudeLines (3..64)
• CircleSegments (8..256)
• Color / Thickness / Depth

3.15 DrawHelix

Draws a 3D helix (spring-like) as a polyline.

Parameters

• WorldLocation / WorldRotation
• Radius
• Pitch: vertical rise per turn
• Turns (>=1)
• SegmentsPerTurn (4..512)
• Color / Thickness / Depth

3.16 DrawElectricArc

Draws a lightning/electric arc: a jittered polyline, optionally layered.

Parameters

• StartLocation / EndLocation
• Color
• Segments (2..512)
• JitterAmplitude: jitter magnitude
• Seed: random seed for reproducibility
• Thickness / Depth
• Layers (1..8)
• LayerAmplitudeMultiplier: amplitude decay per layer (e.g., 0.6)

Notes

• Endpoints are stable; jitter is applied to interior points with a sin(t*pi) falloff (max in the middle).

4) Where to call these nodes (Blueprint best practice)

• One-shot debug draw: BeginPlay or a custom event.
• Continuous debug draw: Tick (useful for live visualization).
  • Keep segment counts reasonable; frequent drawing can be costly.

5) Common issues / troubleshooting

1. Nothing shows

   • Ensure you call from a valid World context (Actors typically are fine).
   • Increase Thickness, ensure Color.A (alpha) is not 0.
   • Try adjusting Depth if occluded.

2. DrawLines does nothing

   • Points.Num() must equal PointsColor.Num().

3. Circles/spheres look jagged

   • Increase Segment / CircleSegments.

6) Quick node list (for search)

• DrawPoint
• DrawLine
• DrawLines
• DrawCircle
• DrawSphere
• DrawBox
• DrawPrisms
• DrawPolygon
• DrawPizza
• DrawSpline
• DrawArrow
• DrawFOVSector
• DrawFOVBoxFrustum3D
• DrawLatLongSphere
• DrawHelix
• DrawElectricArc