GIMP Drop Shadow Grow Shape Settings Guide

In GIMP, controlling the geometry of a shadow's expansion involves configuring both the Grow shape selector and the Grow radius slider inside the GEGL Drop Shadow filter. This article outlines where to locate these settings, how they function together, and what visual results the Circle, Square, and Diamond options produce on your layers.

Accessing the Filter

To open the tool, navigate to the top menu and select Filters > Light and Shadow > Drop Shadow.... This opens the GEGL-based dialog containing all shadow configuration parameters.

The Controlling Settings

Two primary settings work in tandem to govern the shape:

  1. Grow radius: This slider determines how many pixels the shadow expands outward from the original alpha mask before the blur is applied. For the grow shape to be visible, Grow radius must be set to a value greater than 0. If the grow radius is 0, changing the shape produces no visible effect.
  2. Grow shape: Located directly beneath or alongside the grow radius controls, this dropdown menu dictates the mathematical metric used to expand the shadow boundaries.

Grow Shape Options

  • Circle: Uses Euclidean distance to expand the shadow equally in all directions. It rounds off sharp corners and produces natural, smooth edges. This is the default setting and works best for organic objects and standard UI elements.
  • Square: Uses Chebyshev distance to expand the boundary along strict horizontal and vertical bounds. It preserves and accentuates hard 90-degree corners, making it suitable for rectangular cards, pixel art, or blocky graphic design elements.
  • Diamond: Uses Manhattan distance to expand the bounds along a 45-degree angle. This creates pointed, diamond-like corners on extended shapes, ideal for stylized geometric effects or isometric graphics.

To make the geometric profile of the chosen shape more distinct, keep the Blur radius low. Higher blur radius values will soften the edges, blending out the defined corners created by the Square and Diamond settings.