Followshape

Followshape is a term used in computer graphics and animation to describe a relationship in which one element, the follower, conforms its position and possibly orientation to the evolving silhouette or outline of another element, the target. The goal is for the follower to trace the target’s shape while preserving a consistent spatial offset or alignment, enabling effects such as trailing figures, silhouette-based cameras, or shape-constrained particles.

In practice, a followshape relationship can be achieved through constraints or procedural routines that map points on the follower to points on the target's contour. Common approaches include building a parametric representation of the target’s shape (for example, using splines or polygons), computing the closest point or a sampled set along the contour, and then applying a transform to the follower so that its reference point sits on or near that contour. Orientation can be aligned to the tangent of the target contour to maintain smoothness, and temporal smoothing is often applied to reduce jitter.

Applications include animation rigs where a limb or accessory follows a character’s outline, camera systems that track and emulate the subject’s silhouette, particle effects that cling to a shape, and user interface elements that mimic changes in the shape of another component for visual coherence.

Variants may emphasize just position following, only orientation following, or full pose matching. Challenges include handling rapidly changing shapes, occlusion, performance for complex contours, and maintaining stable motion during deformation.

Related concepts include constraint-based animation, shape matching, contour tracking, spline representations, and morphing.