Collision handling for free-form deformation embedded surface

Recently, free-form deformation (FFD)-based simulation has received a lot of attention to achieve real-time animation of complex objects, and many researches have improved the accuracy of modelling complex material property. Previously, a free-form deformation axis aligned bounding box (FFD AABB) was proposed to approximate the FFD-embedded surfaces. Using FFD AABB, an efficient update of bounding box is achieved with balancing between accuracy and computational cost. The authors extended the FFD AABB with a more conservative collision handling method between FFD AABBs to deal with the cases that the nodes on one side of FFD AABB are out-of-plane. In addition, the authors adopted a broad-phase culling algorithm to cope efficiently with both self-collision and inter-collision using parallel spatial hashing.