A B S T R A C TTerrain generation is a fundamental requirement of many computer graphics simulations, including computer games, flight simulators and environments in feature films. There has been a considerable amount of research in this domain, which ranges between fully automated and semi-automated methods. Voxel representations of 3D terrains can create rich features that are not found in other forms of terrain generation techniques, such as caves and overhangs. In this article, we introduce a semi-automated method of generating features for volumetric terrains using a rule-based procedural generation system. Features are generated by selecting subsets of a voxel grid as input symbols to a grammar, composed of user-created operators. This results in overhangs and caves generated from a set of simple rules. The feature generation runs on the CPU and the GPU is utilised to extract a robust mesh from the volumetric dataset.

Figure 1: Procedurally generated features with our method: arches (left), an overhang (middle) and a cave (right). ABSTRACTIn this work we present separate procedural methods to generate features that are found in natural terrains which are difficult to reproduce with heightmap-based methods. We approximate overhangs, arches and caves using procedural functions and a reduced set of parameters. This produces visually plausible terrain feature topologies as well as a high degree of artistic control. Our approach is more intuitive and art-directable than other existing volumetric methods that are more complex to integrate into existing voxel engines, due to the framework changes necessary, or rely on automatic procedural generation, thus reducing the ability to provide creative input.