The visual effects industry has experienced a strong shift towards the creation of many shots with several digital creatures with complex grooms (i.e. fur and hair). Because of it is common for these grooms to change in shape over the duration of a shot (e.g. from dry to wet), techniques to interpolate across different sets of curves are needed.
While researchers have extensively focused on algorithms for polygonal mesh deformation, very little can be found for curves, and basic linear interpolation techniques produce unrealistic results that do not emulate the expected behavior of groom filaments changing in shape and style.
In this paper we present an iterative algorithm that allows for the interpolation across different curve shapes with the ability to preserve key features like strand’s curvature and segment lengths. We also introduce the concept of partial blendshape linear interpolation to help the system to rapidly converge to the optimal solution in few iterations.
We present detailed results and production use-cases in creatures' visual effects.