Paintbrush Tool

The Paintbrush is the primary painting tool, designed for responsive, intelligent brushwork with full control over pressure, velocity, tilt, and spacing dynamics.

Overview

The Paintbrush tool supports raster, procedurally generated, and animated brush types. Strokes can be stabilized, smoothed, and post-processed. Brush dynamics respond to stylus input, giving precise control over opacity, size, color, angle, and other properties during a stroke.

Brush Types

Raster Brushes (.raster)

Bitmap brush images that supports alpha transparency.

Generated Brushes (.param)

Procedurally rendered shapes (Circle, Square, Diamond, Triangle) with adjustable parameters: hardness, aspect ratio, angle, roundness, and corner radius. Generated brushes are lightweight and scalable.

Animated Brushes (.anim)

Sequential frame sequences that advance during strokes. Frames can be cycled incrementally (frame advances per dab), randomly selected per dab, or indexed by dynamics (pressure, velocity, tilt, angle).

Painting Cursor

The cursor adapts to the current tool state to provide clear, contextual feedback:

Brush outline: The cursor tracks the exact brush shape and size, giving a live preview of where paint will land.
Erase mode: When erasing is active, the outline switches to a dashed circle to visually distinguish erase strokes from paint strokes.
Simple Brush Boundary: For complex or very large brushes where rendering the accurate outline is costly, enable Simple Brush Boundary (in Additional Options) to use a plain circle instead.

Tool Options

Top-Level Controls

Present at all times, outside any expander:

Mode: Paint blending mode (Normal, Multiply, Screen, etc.)
Opacity: Overall stroke opacity (0–100).

Brush Properties

In the Brush Properties expander (expanded by default):

Size: Brush diameter in pixels.
Aspect Ratio: Squash or stretch the brush shape (-1.0–1.0). 0 = unmodified; negative values rotate the squash 90°.
Angle: Rotates the brush stamp (-180–180°). Independent of stroke direction dynamics.
Hardness: Soft fade (0.0) to sharp edge (1.0).
Spacing: Distance between painted dabs as a percentage of brush size. Lower = smoother strokes; higher = scattered pattern.
Texture Bias: Bias the stamp texture response; 50 is neutral. Lower values favour texture breakup and a skimmed surface by pulling toward the toe of the value curve; higher values clamp toward solid fills by pushing toward the shoulder. The visible effect depends on the texture’s tonal range.
Jitter: Randomly offsets each dab position by up to this many pixels (0–1024).
Eraser: Size multiplier applied when this brush is used as an eraser (0.1–10.0). Not shown on the Eraser tool itself.

Dynamics

In the Dynamics expander:

Dynamics: Master enable for the active dynamics preset.
Dynamics Preset: Selects which input mappings are used.
Multiply by Pressure: Extra pressure multiplication toggle (shown when Dynamics is enabled).

Stroke Behaviour

In the Stroke Behaviour expander:

Build-Up: When on, each dab accumulates opacity rather than being composited as a single stroke.
Post Process: Applies stabilization, velocity compression, and replay correction after the stroke is complete, improving consistency without latency.
- Turn Threshold: Angle threshold (0–180°) for direction correction at sharp corners. 0 = skip direction fix.
- Preview Threshold: Suppresses the post-process preview when stroke velocity exceeds this value (0 = always preview).

Calligraphic

When active, dab stamping is replaced by a continuous geometric corridor:

Dynamic Opacity: Modulates opacity within the stroke based on velocity and direction changes. Works best on fine, controlled strokes; results are less predictable on rapid scribbles. Experimental.
Velocity Growth (0–100%): Maximum allowed size increase per sample as a percentage of the previous sample’s size. Limits how quickly a velocity-driven size dynamic can grow, preventing sudden jumps when the stroke accelerates.
Velocity Shrink (0–100%): Maximum allowed size decrease per sample. Limits how quickly the size can drop when the stroke decelerates.

Stabilization & Smoothing

Direction Stabilization Distance (0–100 px): Minimum pointer travel before direction-sensitive behavior starts, helping avoid early angle jumps.

Smoothing

Enables real-time input smoothing applied to the stroke path as you paint. Expands to reveal:

Depth (2–256): Number of previous input samples considered when computing the smoothed position. Higher values produce a longer, more committed lag.
Position (0–100): Intensity of smoothing applied to the brush position. Higher values round out sharp direction changes.
Pressure (0–100): Smoothing applied to the stylus pressure signal, reducing pressure spikes and jitter.
Direction (0–100): Smoothing applied to the stroke direction, stabilising angle-sensitive dynamics.

Dynamics

Assign stylus input or other live values to painting parameters:

Pressure (stylus): Controls size, opacity, rate, hardness, color, and more based on stylus pressure.
Velocity: Maps stroke speed to brush properties.
Tilt: X and Y tilt angles of the stylus affect angle and other parameters.
Wheel: Mouse wheel or stylus wheel input.
Direction: Angle of stroke direction.
Fade: Fade opacity or size over a fixed number of dabs.

Each dynamic input can be mapped to multiple properties independently. Open Tool Options → Dynamics to configure.

Stroke Modulation

In the Stroke Modulation expander (shown only when Dynamics is enabled):

Relative Initial Angle: The Initial Angle value is interpreted relative to the stroke direction rather than as an absolute canvas angle.
Fade Initial Angle: Fades from the Initial Angle at stroke start toward the live dynamic angle over the course of the stroke. Enabling this forces Relative Initial Angle on.
Brush Initial Angle (-180–180°): The brush angle at the very start of a stroke, before dynamics take over.
Initial Angle Blend (0.0–1.0): Controls how quickly the brush angle transitions from the initial angle to the dynamic angle. 0 = holds the initial angle; 1 = immediately uses the fully dynamic angle.
Fade Length: Distance in canvas units over which the fade plays out.
Repeat: How the fade is repeated once the fade length is exhausted (None, Loop, Sawtooth, Triangle).

Fade Multipliers

Four checkboxes that gate or modify how the fade value is applied:

Fade Reverse: Reverses the fade direction so strokes start faded and become fully opaque.
Fade Multiply: Multiplies the fade output into the affected property rather than replacing it.
Fade Multiply Angular: Applies the fade multiplier only to angular dynamics (angle, tilt).
Fade Multiply Ratio: Applies the fade multiplier only to ratio-type properties (aspect ratio).

Colour Mapping

Available for Paintbrush and Smudge tools when Dynamics is active:

Gradient: The gradient resource used for colour mapping along the stroke.
Blend Color Space: Colour space in which gradient colours are interpolated during painting.

Brush Heads

Brush Heads places multiple independent brush heads on a circular orbit ring centred on the stroke path. Every head paints a full dab at its own position each time the stroke advances, producing multiple parallel or fanned strokes simultaneously.

The orbit radius is determined by the global brush size minus the head size: larger heads sit closer to the centre; smaller heads orbit further out. Heads space evenly around the ring. With two heads you get one on each side of the stroke, creating a symmetrical spread that behaves like a calligraphy nib. The Follow Direction slider rotates the whole ring to stay perpendicular to the stroke, so the nib tracks direction naturally as you paint. Adding more heads fans them progressively around the ring, up to a full spray circle at 16.

Brush Heads controls where each head is placed around the stroke. If Pivot X or Pivot Y is moved away from the default centre, every head still follows the same formation, but each stamped dab now lands using the chosen internal contact point instead of the geometric centre of the brush image.

Controls appear in the Brush Heads expander in the tool options panel.

Count: Number of simultaneous brush heads (1–16).
Head Size: Rendered size of each head relative to the global brush size (0.1–1.0).
Orbit Aspect Ratio (0.1–1.0): Shapes the formation orbit from circle to ellipse. 1.0 = circular orbit; lower values squash the minor axis.
Formation Angle (0–360°): Static orientation of the formation ring, used when Follow Direction is below 1.0.
Follow Direction (0.0–1.0): How strongly the formation ring tracks the stroke travel direction. At 1.0 the ring is always perpendicular to the direction of travel; at 0.0 it locks to the static Formation Angle value.
Pressure Variation: Per-head size variation applied as an independent pressure bias through the dynamics curves.
Opacity Variation: Per-head opacity variation, independent of size variation.

Scatter

Main scatter controls in the Brush Heads expander:

Scatter Angle (0–360°, default 10°): Rotates only the random scatter component (not Fill Spacing). Per-head/per-dab angles are outward-biased with controlled crossover to avoid rigid mirrored plumes. Clamped to 360°.
Scatter Distance (0–10000 px): Random forward displacement from each head’s fill-spacing position. Re-rolled every dab.
Scatter Randomness (0.0–1.0): Additional per-dab variation layered on top of the base scatter distance and angle, producing a looser, more organic spray.
Velocity Influence (0.0–1.0): Scales the scatter by stroke velocity. At 1.0, fast strokes scatter heads much further than slow strokes; at 0.0, scatter is constant regardless of speed.
Scatter Size Balance (0.0–1.0): Controls suppression steepness for heads above threshold. At 1.0, all heads scatter equally; lower values increasingly suppress larger heads while heads at/below threshold stay at full scatter distance.

Additional Options

In the Additional Options expander (collapsed by default), controls are grouped as overflow sections that are changed less often. This keeps the main expanders focused on frequently adjusted painting controls.

Brush Properties (overflow)

Lock Angle to Screen Space: Locks brush angle to screen space, so angle stays level while the canvas rotates/flips. No effect when Dynamics controls angle.
Random Flip Horizontal: 50% chance to mirror each stamp left-to-right per dab.
Random Flip Vertical: 50% chance to flip each stamp upside-down per dab.
Random Rotation: Randomly rotates each stamp by 0°, 90°, 180°, or 270° per dab.
Pivot X (0.0–1.0): Horizontal contact point within the brush image. 0.0 = left edge, 0.5 = centre (default), 1.0 = right edge. The chosen point is what aligns with the paint position on the canvas, so moving it away from centre shifts every dab in that direction. Rotations and flips stay visually anchored to the pivot because the placement offset is applied after the transform.
Pivot Y (0.0–1.0): Vertical contact point within the brush image. 0.0 = top edge, 0.5 = centre (default), 1.0 = bottom edge. Works together with Pivot X to define the exact part of the dab that sits on the stroke path.
Uniform Jitter: When on, dab offsets from the Jitter slider are drawn from a uniform distribution (every offset equally likely within the range). When off, the distribution is biased toward the centre.
Reset Animation: For animated brushes: when on, the animation restarts from frame 0 at each new stroke; when off, it continues from where the previous stroke ended.

When either pivot value differs from centre, the brush preview shows a crosshair overlay marking the active stamp contact point.

Brush Heads (overflow)

Formation:

Bristle Stiffness: How rigidly the orbit radius follows the dynamics-scaled brush size. 0 = orbit expands and contracts with pressure; 1 = orbit stays fixed to the base size.
Fill Spacing (0.0–1.0): Spreads heads across the gap between consecutive dab positions. Each head’s stable character value determines its lean direction; at 1.0 heads fill the full spacing interval. Character is stable per seed.

Scatter:

Scatter Size Threshold (0.01–100 px): Threshold radius for full scatter distance. Heads at or below this radius use full scatter distance; larger heads are progressively pulled closer to the stroke.

Randomization:

Character Seed (0–255): Fixed seed for per-head character (size, fill-spacing position). The same seed reproduces the same formation every stroke. Desensitized when Randomize Head Character is on.
Randomize Head Character: Re-draws per-head character values (size, scatter position) every stamp so the formation is fully chaotic along the stroke. Overrides Character Seed.
Randomize Animation Frames: For animated brushes: each head advances its animation frame independently.

Dynamics (overflow)

Controls that extend the main Dynamics expander, grouped here as they are rarely adjusted:

Preview Random Size: Shows randomised size variation in the brush outline preview when the active dynamics preset drives size randomly.
Preview Random Rotation: Shows randomised rotation variation in the brush outline preview when the active dynamics preset drives angle randomly.

Stroke Behaviour (overflow)

Restore Last Used Colors: Restores the foreground and background colors from the previous session at startup, instead of defaulting to black and white.
Simple Brush Boundary: Uses a plain circle for the brush cursor outline instead of rendering the full brush shape. Useful for complex or large brushes where the accurate boundary is expensive to draw.

Layers Palette Editor