Sketch-based character prototyping by deformation

Abstract

Most 3D character editing tools are complex and non-intuitive. It takes lot of skill and labor from the artists to create even a draft 3D humanoid model. This paper proposes an intuitive 2D sketch driven drafting tool that allows users to quickly shape and proportion existing 3D models. We leverage on our existing vector shape representation to describe character body-part segments as affine-transformed circle-triangle-square shape blends. This is done for both the input 2D doodle as well as for the extracted point clouds from 3D library mesh. The simplified body part vector shapes help describe the relative deformation between the source (3D library mesh) and the target (2D frontal sketch). We design and implement two different approaches to achieve the actual deformation and compare the results. One approach is based on automatically setup Free Form Deformation cages, while the other is via shape-based analysis and geometry warping of corresponding body parts. To perform body-part shape analysis, we first segment the mesh with Baran and Popovic?s algorithm for automatic fitting of an input skeleton to a given 3D mesh, followed by our existing 2D shape vector fitting process. There are several promising character design applications of this paper; e.g. accelerated personality pre-visualization in movie production houses, intuitive customization of avatars in games and interactive media, and procedural character generation.