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Curve brush

The curve brush is a brush engine which creates strokes made of evenly spaced lines. It has, amongst other things been used as a replacement for pressure sensitive strokes in lieu of a tablet.


First off, the line produced by the Curve brush is made up of 2 sections:

  • The connection line, which is the main line drawn by your mouse

  • The curve lines I think, which are the extra fancy lines that form at curves. The curve lines are formed by connecting one point of the curve to a point earlier on the curve. This also means that if you are drawing a straight line, these lines won't be visible, since they'll overlap with the connection line. Drawing faster gives you wider curves areas.


You have access to 3 settings from the Lines tab, as well as 2 corresponding dynamics:

  • Line width: this applies to both the connection line and the curve lines.

    • Line width dynamics: use this to vary line width dynamically.
  • History size: this determines the distance for the formation of curve lines.
    • If you set this at low values, then the curve lines can only form over a small distances, so they won't be too visible.

    • On the other hand, if you set this value too high, the curve lines will only start forming relatively "late".

    • So in fact, you'll get maximum curve lines area with a mid-value of say... 40~60, which is about the default value. Unless you're drawing at really high resolutions.
  • Curves opacity: you can't set different line widths for the connection line and the curve lines, but you can set a different opacity for the curve lines. With low opacity, this will produce the illusion of thinner curve lines.
    • Curves opacity dynamics: use this to vary Curves opacity dynamically.

In addition, you have access to two checkboxes:

  • Paint connection line, which toggles the visibility of the connection line

  • Smoothing, which... I have no idea actually. I don't see any differences with or without it. Maybe it's for tablets?


Drawing variable-width lines

And here's the only section of this tutorial that anyone cares about: pretty lineart lines! For this:

  • Use the Draw Dynamically mode: I tend to increase drag to at least 50. Vary Mass and Drag until you get the feel that's most comfortable for you.


  • Set line width to a higher value (ex.: 5), then turn line width dynamics on:

    • If you're a tablet user, just set this to Pressure (this should be selected by default so just turn on the Line Width dynamics). I can't check myself, but a tablet user confirmed to me that it works well enough with Draw Dynamically.

    • If you're a mouse user hoping to to get variable line width, set the Line Width dynamics to Speed.
    • Note: the Speed trick works well on Linux, but on my Windows XP system the Speed setting is actually unstable, which makes this trick unusable. I don't know if this affects all Windows systems or just me, but if you encounter this problem, please confirm it at this bug report.


  • Set Curves opacity to 0: This is the simplest way to turn off the Curve lines. That said, leaving them on will get you more "expressive" lines.

Additional tips:

  • Zig-zag a lot if you want a lot of extra curves lines.

  • Use smooth, sweeping motions when you're using Draw Dynamically with Line Width set to Speed: abrupt speed transitions will cause abrupt size transitions. It takes a bit of practice, and the thicker the line, the more visible the deformities will be. Also, zoom in to increase control.

  • If you need to vary between thin and thick lines, I suggest creating presets of different widths, since you can't vary the base line width from the canvas.


  • Use the Draw Dynamically mode

  • Set Curves opacity to 100

  • Optionally decrease History size to about 30

The curve lines will fill out the area they cover completely, resulting in a line with variable widths. Anyway, here are some comparisons:


And here are examples of what you can do with this brush:


This page was last modified on 8 June 2014, at 15:58. Content is available under Creative Commons License SA 4.0 unless otherwise noted.