Smudge Pencil is a Geometry Nodes setup applied to a Grease Pencil object that allows users to draw 2D-style smear frames directly over 3D animations. By drawing strokes in camera view, the setup generates underlying geometry equipped with a custom refraction shader. This shader distorts the objects behind the strokes, creating a visual smudging effect that follows the stroke's direction, size, and strength.

The setup is constrained to the active camera to simplify the drawing process. It includes seven adjustable brushes and effects, alongside two example scenes demonstrating basic and advanced use cases. While compatible with both EEVEE and Cycles, complex scenes with multiple depth layers require Cycles and compositing via ViewLayers, as EEVEE does not support alpha in refractions or multiple overlapping refraction layers.