Patent ID: 8115765

Claim:
A non-transitory computer readable medium including a computer-implemented system for generating terrain in a virtual world, the system comprising: a plurality of procedural rules configured to generate a virtual terrain in the virtual world, wherein said plurality of procedural rules is organized into hierarchical layers such that a single location in the terrain can have multiple procedural rules that overlap and the terrain has at least one location that has overlapping rules, each hierarchical layer defining boundaries, filters, and affectors; and a terrain generator configured to process the plurality of procedural rules so as to generate a virtual representation of the terrain, wherein when multiple procedural rules overlap the terrain generator specifies a blend region and initiates a boundary influence computation to blend heights and colors to prevent hard, visible discontinuities at the overlap of the procedural rules, wherein the plurality of procedural rules is textually represented so that the boundaries, filters, and affectors are assigned numeric values that represent desired attributes in a logical, textual format, and wherein the terrain is modified by adding or deleting at least one rule from the plurality of procedural rules.