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🎯 Triggers & Strokes

Simple Painter separates input detection (Triggers) from stroke interpolation (Stroke Methods), allowing you to mix and match any trigger with any stroke behavior.

🔫 Triggers​

All triggers inherit from the abstract PaintTrigger base class and are responsible for detecting user input and emitting stroke events to the painting pipeline.

PaintTriggerRaycast​

Screen-space pointer or screen-center (FPS) input using Unity's new Input System. Ideal for first-person and third-person painting scenarios.

  • Supports both pointer position and fixed screen-center modes
  • Automatically handles camera raycasting against paintable surfaces
  • Configurable input action references for press/release

PaintTriggerCollision​

Physics 3D collision-based triggering, perfect for tire tracks, scratch marks, and drag effects.

  • Filters impacts by minimum impact speed threshold
  • Supports surface layer mask to restrict which surfaces receive paint
  • Processes OnCollisionEnter, OnCollisionStay, and OnCollisionExit events

PaintTriggerParticle​

Particle system collision integration that processes all impacts as a single burst stroke.

  • Hooks into OnParticleCollision events
  • Batches all particle impacts in a single frame into one stroke
  • Great for splatter effects, rain drips, and environmental painting

🔄 Trigger Lifecycle​

All triggers follow the same three-phase lifecycle by calling protected methods on the base PaintTrigger class:

// Bắt đầu nét vẽ — khởi tạo stroke mới với ray và collider mục tiêu
EmitBegin(ray, targetCollider);

// Cập nhật vị trí stroke mỗi frame
EmitUpdate(ray);

// Kết thúc nét vẽ — finalize và commit stroke
EmitEnd();
info

Each trigger auto-resolves its IStrokeSampler from the same GameObject or a parent in the hierarchy. When the trigger's OnDisable is called, it automatically invokes EmitEnd() to ensure no stroke is left dangling.

✏️ Stroke Methods​

Stroke methods control how stamps are interpolated between input samples. Each method produces a different visual character.

BezierMethod​

Quadratic Bézier curve interpolation that produces smooth, natural strokes. The curve is fitted through the last three input samples, creating organic brush paths even with coarse input sampling.

LineMethod​

Draws a straight line from the anchor point to the current position. The line is regenerated each frame, making it ideal for rulers, guides, and technical drawing tools.

DotMethod​

Places a single stamp per update with no interpolation between samples. Use this for stippling, pointillism, or any effect where discrete stamps are desired.

AnchoredMethod​

Anchors at the click point — dragging controls the size and rotation of the stamp. Perfect for placing decals, logos, or precisely-sized stamps.

🔀 Switching Stroke Methods at Runtime​

The StrokeSampler MonoBehaviour wraps a StrokeMethodConfig (ScriptableObject), enabling hot-swap at runtime:

// Chuyển đổi config stroke — thay đổi hành vi nét vẽ mà không cần tạo lại component
strokeSampler.SwitchConfig(newBezierConfig);
tip

Always use SwitchConfig() to change stroke behavior instead of mutating the ScriptableObject asset directly. This ensures proper state cleanup between configurations.

📊 StrokeMethodConfig Properties​

Each property supports multiple Dynamic Modes for procedural variation:

PropertyRangeDynamic Modes
Size0 – 10Constant, Distance, Speed, Time, Random
Alpha0 – 1Constant, Distance, Speed, Time, Random
RotateAngle-180° – 180°Constant, Distance, Speed, Time, Random
BrushDynamics0 – 1Constant, Distance, Speed, Time, Random

Additional Configuration​

  • StampShape: Defines the shape mask applied to each stamp (circle, square, custom texture).
  • StampAlignmentConfig: Controls how stamps orient relative to the stroke direction or surface normal.
  • TextureMapping: Configures how the brush texture is sampled and mapped onto each stamp.

⚙️ Stamp Generation Pipeline​

The stamp generation process follows 5 sequential steps inside BaseStrokeMethod.TryRecordStamp():

  1. Sample Input — Read the current ray/position from the trigger
  2. Interpolate Path — Apply the stroke method's interpolation algorithm (Bézier, Line, etc.)
  3. Spacing Check — Determine if enough distance/time has passed to place a new stamp
  4. Apply Dynamics — Evaluate all dynamic property curves (Size, Alpha, Rotation, BrushDynamics)
  5. Record StampData — Write the final StampData struct into the surface's StampBatch

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