Hybrid sketch-based and procedural modeling of plants

Creating 3D plant models is often a hard and laborious task due to the great number of elements involved and their intricate shapes. To make it easier and more intuitive, the use of sketch-based interfaces and modeling (SBIM) combined with procedural modeling techniques is proposed. In SBIM, 3D models are constructed after a given small set of strokes sketched by the user.;Three approaches are presented in this thesis. Firstly, a novel approach based on the traditional illustration technique of concept sketch is used to model single-compound plant structures with spiral phyllotactic arrangements of organs. The user sketches key construction lines for the main plant body and lateral organs. From them, a 3D organ arrangement is automatically constructed and rendered as pen-and-ink line drawings. In the second approach, concept sketches are applied to the parameterization of L-system models. The information extracted from the sketch is codified in a set of functions that control specific attributes of the grammar interpretation. Plant organs, modeled from four basic sketch strokes or from the lateral deformations of a reference sheet, are converted to a file format readable by the L-system engine. This extends the previous interface to model single-compound L-system plants. Finally, a hybrid approach is proposed integrating sketched organ surfaces with arbitrary L-systems. This integration aims to have at once the elegance of grammar-based plant structure definition and the simplicity of sketch-based organ specification, avoiding the tedious manual definition of branch arrangements and the manipulation of control points. It also allows adding variation and animation to L-system models via interpolation operations.