Pressure Brush Stroke Renderer

What it is for

A drawing app records a stroke as a list of positions and, with a pen, a pressure value for each one. This tool takes such a list and renders the stroke the way Flipline's brushes do: graphite pencil, studio ink, chisel marker, pigment wash or soft airbrush. Pressure makes the line thinner and lighter where you pressed softly.

You type the points as x y pressure, one per line, with all three values between 0 and 1 (x and y relative to the canvas). The result is a deterministic SVG made of small ellipse stamps, an editable .flipline.json drawing with the same stroke, and a .flipline-brush.json recipe you can open in Flipline's Brush shelf. Use it to generate brush previews, test a recipe without a tablet, or let a script or AI agent create strokes. It is a stamp brush, not a physical paint simulation.

Worked example

I drew a broad wave with Pigment wash on a 900 × 300 px canvas, brush width 60 px, opacity 55 %, flow 30 %, texture 50 %, ink #4D7F87, using five points that press hardest in the middle:

0.08 0.7 0.15
0.3 0.45 0.55
0.55 0.4 1
0.8 0.55 0.6
0.94 0.35 0.1

The summary said "126 brush dabs in an editable drawing." The wash places two overlapping dabs per stamp position, so the stroke has 63 stamp positions along its length. At full pressure a dab is 60 px wide; at the light end (pressure 0.1) it shrinks to about 16 px and becomes much more transparent, so the stroke tapers into the paper.

When I turned Use pressure samples off and ran it again, the dab count stayed at 126, because spacing depends on the brush width, not on pressure. But every dab now had nearly the full width, and the stroke became an even band.

The first built-in example, a graphite pencil with default settings, gives 660 dabs: the pencil scatters four small grains around each of its 165 stamp positions.

How to read the result

• Summary: the number of dabs (ellipse stamps) in the stroke. More dabs means a denser, heavier mark and a larger SVG.
• Rendered stroke: the SVG preview on your paper color.
• Download brush SVG: the same picture as a standalone vector file.
• Download editable brush drawing: a one-drawing Flipline project. Open it in the app and the stroke stays editable: you can move, recolor or restyle it.
• Download brush recipe: the brush style, opacity, flow, spacing, texture, pressure switch, seed and width.

Tips and common mistakes

• Every row needs at least x and y. A missing pressure counts as 1; a value above 1, such as 1.2, is rejected.
• Opacity and flow multiply. Opacity 55 % with flow 30 % gives very light single dabs; overlap builds up the color, just like going over a line twice.
• The Texture seed fixes the grain. The same input always gives the same SVG; change the seed for a different texture with the same shape.
• Spacing comes from the chosen brush style. The marker and ink use tighter spacing than the wash.
• Long strokes are capped at 1,024 stamp positions. If a very long stroke looks dotted, use a larger brush width or split it.

FAQ

Can I record real pen pressure here?

No, this tool takes typed values. Flipline's drawing board and the Brush shelf's test paper record pressure from a pen; mouse and touch count as full pressure.

Why do browser and SVG look slightly different?

Both use the same ellipse geometry, but renderers blend transparent shapes a little differently.

Which canvas sizes work?

Widths and heights from 32 to 1,600 px, up to 2 megapixels in total, with 1 to 256 points per stroke.

Is the pigment wash a watercolor simulation?

No. It layers soft, translucent stamps. There is no wet paint, drying or pigment mixing.