GIMP Incremental vs Non-Incremental Painting

This article explains the core differences between the Incremental and Non-incremental painting modes in GIMP's brush tools. Understanding how these two modes affect brush strokes, opacity buildup, and blending allows you to choose the right setting for sketching, digital painting, or photo retouching.

The Core Difference: Opacity Accumulation

The primary difference between Incremental and Non-incremental painting is how GIMP handles opacity during a single continuous brush stroke.

  • Non-incremental Mode (Default): When you set your brush opacity below 100% (for example, 40%) and draw a continuous line without releasing the mouse button or lifting your stylus, the opacity will never exceed 40%, even if you loop back and paint over the stroke you just made. The stroke behaves as a single uniform layer. To add more paint or build up darkness, you must release the input and begin a second, separate stroke.
  • Incremental Mode: When the "Incremental" box is checked in the Tool Options, the brush behaves like a traditional physical marker or repeated glaze. Even during a single continuous stroke, crossing over an area you just painted immediately adds another layer of color, increasing the opacity and density in that overlapping spot until it reaches 100%.

Practical Comparison

To easily visualize how the two modes function, consider setting your brush opacity to 30% with a black color on a white canvas:

  1. In Non-incremental mode: Draw a continuous squiggle over the same spot multiple times without releasing the mouse button. The entire stroke remains a consistent light gray. No matter how many times you pass over the area, it stays capped at 30% gray until you lift the mouse and click again.
  2. In Incremental mode: Draw the exact same continuous squiggle. Everywhere the stroke overlaps itself, the gray tone darkens (to roughly 51%, then 66%, and so on) until it becomes solid black, all within that single drag of the cursor.

When to Use Each Mode

  • Use Non-incremental mode when you need smooth, even coverage across an area. It is ideal for flat coloring, consistent shading, soft airbrushing, and blending, as it prevents accidental blotches or uneven streaks caused by overlapping hand movements.
  • Use Incremental mode when you want a workflow that mimics physical wet media, such as markers, watercolor washes, or charcoal sketching. It is useful for rapidly building up depth, shadows, and values organically without having to constantly lift your stylus or adjust brush opacity sliders.

How to Toggle the Setting

To switch between modes, select any compatible brush tool (such as the Paintbrush, Pencil, or Eraser) and navigate to the Tool Options panel. Locate the Incremental checkbox directly beneath the tool opacity and brush size controls. Checking the box activates Incremental mode; leaving it unchecked keeps the tool in standard Non-incremental mode.