  Procedural terrain generation is the process of generating a digital
representation of terrain using a computer program or procedure, with little to
no human guidance. This paper proposes a procedural terrain generation
algorithm based on a graph representation of fluvial erosion that offers
several novel improvements over existing algorithms. Namely, the use of a
height constraint map with two types of locally defined constraint strengths;
the ability to specify a realistic erosion strength via level of rainfall; and
the ability to carve realistic gorges. These novelties allow it to generate
more varied and realistic terrain by integrating additional parameters and
simulation processes, while being faster and offering more flexibility and ease
of use to terrain designers due to the nature and intuitiveness of these new
parameters and processes. This paper additionally reviews some common metrics
used to evaluate terrain generators, and suggests a completely new one that
contributes to a more holistic evaluation.
