GIMP Stylus Pressure for Brush Opacity and Flow

Configuring dynamic stylus pressure to control both brush opacity and flow simultaneously in GIMP allows digital painters to achieve natural, buildable blending similar to traditional media. This guide covers how to create a custom Paint Dynamic, map stylus pressure to both opacity and flow within the Dynamics Matrix, and fine-tune individual response curves to ensure a responsive, seamless drawing experience.

Step 1: Open the Paint Dynamics Panel

Default presets in GIMP are locked against editing, so you must create a custom dynamic preset to modify the curves.

  1. Open GIMP and navigate to Windows > Dockable Dialogs > Paint Dynamics.
  2. In the Paint Dynamics dock, click the Create a new dynamic button (represented by a blank document icon) at the bottom, or duplicate an existing profile.
  3. Name your new profile (for example, "Pressure Opacity and Flow").

Step 2: Configure the Mapping Matrix

Opening or double-clicking your new preset opens the Paint Dynamics Editor.

  1. Locate the Mapping Matrix grid, which maps hardware inputs (rows) to brush behaviors (columns).
  2. Find the row labeled Pressure.
  3. Check the box under the Opacity column.
  4. Check the box under the Flow column.

Enabling both boxes links your stylus pressure to the overall transparency (opacity) and the accumulation rate of the pigment per dab (flow).

Step 3: Calibrate the Dynamic Pressure Curves

To avoid abrupt transitions, you must adjust the individual response curve for each attribute.

  1. Below the matrix in the Paint Dynamics Editor, locate the Dynamics Curves section.
  2. From the dropdown menu, select Opacity. A graph plotting stylus pressure (horizontal axis) against opacity output (vertical axis) will appear.
  3. Click and drag the curve to adjust the response. A gentle "S-curve" or slight exponential curve prevents maximum opacity from triggering too early.
  4. Switch the dropdown menu to Flow.
  5. Adjust the Flow curve. A steeper initial incline for flow often works best, allowing ink to start laying down at light pressure while opacity remains low, yielding soft, glaze-like strokes that darken as pressure increases.

Step 4: Apply and Test the Preset

  1. Select the Paintbrush tool from the Tools panel.
  2. In the Tool Options dock, expand the Dynamics section.
  3. Click the dynamics icon and select your newly configured preset from the list.
  4. Set the base Opacity and Flow sliders in the Tool Options to 100% to allow the dynamics to manage the full dynamic range (0% to 100%) based on your pen pressure.
  5. Test the brush on the canvas, adjusting the curves in the Dynamics Editor until the tactile response matches your painting style.