Simplified definition of parameter spaces of a procedural model using sketch-based interaction

This paper presents a novel technique to intuitively insert meta-parameters into a procedural model with the help of sketch-based interaction. The procedural model is represented in a GML (Generative Modeling Language) representation, which is a script language that focuses on the description of three-dimensional models. A GML model consists of a sequence of procedural modeling commands, for example extrusions. These are called with a set of local offset positions, which can be converted to global space and anchored in the surface mesh by finding reference vertices on the mesh. The system uses a deformation technique to deform the surface of the model. During the deformation, the reference vertices provide the global offset positions, whose path can be approximated by a B-spline. Exchanging the initial values of the commands by this B-spline, defines a continuous parameter space of the meta-parameter. The deformation process is supported by a mesh segmentation to create pre-defined deformation targets. Using sketch-based methods, these can be adapted to the user's needs. The results show that the system closely imitates the deformation with the help of the modeling commands. Furthermore, the system was evaluated to be intuitive and easy to use.