Brush Configuration

Brush config controls the stamp used for each rendered point.

Configuration playground

Change color, size, spacing, flow, opacity, roundness-related behavior, and eraser mode to see how brush config affects each stamp.

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ColorSizeSpacing

SmoothSpacingPressure sensitivityBlend modesource-overmultiplyscreenoverlayFilternoneblurbrightcontrast

interface BrushBasicConfig {
  size: number;
  opacity: number;
  flow: number;
  color: string;
  angle: number;
  roundness: number;
  spacing: number;
  eraser: boolean;
  rotation?: RotationConfig;
}

BrushConfig is the partial version accepted by constructors and loadConfig.

Defaults

{
  size: 20,
  opacity: 1,
  flow: 1,
  color: "#000000",
  angle: 0,
  roundness: 1,
  spacing: 0.12,
  eraser: false,
}

Fields

Field	Description
size	Base stamp size in pixels. Pressure also scales size.
opacity	Stroke opacity from 0 to 1.
flow	Paint buildup from 0 to 1. Pressure also scales flow.
color	CSS color used to fill ellipse stamps or recolor image stamps.
angle	Base stamp angle as a fraction of one turn, from 0 to 1.
roundness	Ellipse/image width ratio from 0 to 1.
spacing	Distance between stamps as a multiplier of brush size.
eraser	When true, the brush erases content instead of painting it.
rotation	Optional stamp rotation behavior.

opacity, flow, and roundness are clamped to 0..1 while rendering. Pressure is also clamped to 0..1; it scales both stamp size and flow.

Flow And Dense Spacing

opacity is a stroke-level ceiling. flow is the rate at which paint builds up through the stamps that make up the stroke.

Since 0.8.7, Fuderu normalizes flow against the active brush size and spacing. This prevents very dense stamp overlap from making low-flow strokes immediately flatten into solid color. Modules still receive the pressure-adjusted flow value in onChangeConfig; the brush renderer applies the spacing-aware per-stamp alpha when the point is queued for drawing.

Rotation

rotation?: {
  mode?: "fixed" | "flow" | "random";
  offset?: number;
  jitter?: number;
  smoothing?: number;
};

• fixed: uses rotation.offset when a rotation config is present. Omit rotation to use the brush's angle field.
• flow: follows the direction of the stroke.
• random: varies rotation between stamps.
• offset: adds an angle offset in radians.
• jitter: adds random rotation variation in radians.
• smoothing: smooths flow-based direction changes.