Layered shape grammars for procedural modelling of buildings

The effort of creating virtual city environments is reduced using procedural modelling techniques. However, these typically use split-based approaches which can impose limitations on the final geometry, usually enforcing a grid-like structure and require complex geometry to be imported. Layered shape grammars can increase the variability of procedural buildings, while the vectorial definition of shapes introduces the possibility of creating complex shapes that seamlessly blend into the model. We evaluate the contributions with a modelling example and a comparison with split-based procedural modelling techniques. Results show that layers allow more flexibility than split-based techniques in creating variations. Vectorially defined shapes are a step forward in shape grammar expressiveness.