Output details

CONTINUOUS SKELETON-DRIVEN SKINNING — A GENERAL APPROACH FOR MODELING SKIN DEFORMATION

Originality - Skinning has been a key technique in character animation, responsible for the character’s outer layer deformation. The classic linear blend skinning technique results in undesirable artefacts, where the skin deforms unnaturally near joints. Animators have been aware of such defects for decades and they are tedious to correct manually, which unfortunately remains the most common solution in the Visual Effects industry something which is costly in terms of staff time. Our work conducts a mathematical analysis to reveal the cause of such defects and provides a successful remedy to correct the deformation automatically.

Rigour - The development has been supported by a thorough review of existing literature on skinning techniques. The method uses a temporal formulation to integrate the rotation matrix leading to a robust numerical algorithm, which we have tested using over one million samples. The compatibility and accuracy have been evaluated with complex animation tasks. The benchmark tests prove that our results compare favourably with the non-linear corrections.

Significance - A significant advantage of our method is its compatibility with the common animation production practice. This means it can overcome the existing problems without affecting the production pipeline that has been established for decades. The other rectification methods, such as “spherical blend skinning” and “dual quaternion skinning”, although also effective, require the redesign of the skinning process making them infeasible to use in the industry. A plug-in for animation software Maya has been implemented for artists to use. The work forms a part of the “Retargeting Animated Humans” project funded by the GWR (£117,000, Zhang, Yang). The mathematical formulation and semi-linear solution has brought new insight and understanding of skinning techniques and laid a theoretical foundation for our later work on “skin sliding” and “cage deformation” that further enhance the visual quality of animation.