Sugihara, MasamichiGroot, Erwin deWyvill, BrianSchmidt, RyanChristine Alvarado and Marie-Paule Cani2014-01-282014-01-282008978-3-905674-07-11812-3503https://doi.org/10.2312/SBM/SBM08/065-072Skeletal implicit surfaces offer many advantages for sketch-based modeling systems, such as blending, CSG, and a procedural object hierarchy. Free-form deformation (FFD) is also extremely useful in this context, however existing FFD approaches do not support implicit surface representations, and FFD lattice manipulation is timeconsuming compared to sketch-based techniques. In this paper, we describe an FFD technique suitable for implicit surface representations. To enhance real-time feedback, we split the problem into an approximate formulation used during interactive deformation, and a more robust variational technique which preserves desirable scalar field properties. As an interface to manipulate the deformation, we introduce a sketch-based volumetric peeling interface. The designer's task is to draw a curve on the surface, and pull or push the surface to the desirable position via the curve. Subsequently, the deformation is automatically defined. Results show that a desirable deformation can be easily achieved while preserving implicit properties.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling H.5.2 [Information Interfaces and Presentation]: User Interfaces