  The game and movie industries always face the challenge of reproducing
materials. This problem is tackled by combining illumination models and various
textures (painted or procedural patterns). Gnerating stochastic wall patterns
is crucial in the creation of a wide range of backgrounds (castles, temples,
ruins...). A specific Wang tile set was introduced previously to tackle this
problem, in a non-procedural fashion. Long lines may appear as visual
artifacts. We use this tile set in a new procedural algorithm to generate
stochastic wall patterns. For this purpose, we introduce specific hash
functions implementing a constrained Wang tiling. This technique makes possible
the generation of boundless textures while giving control over the maximum line
length. The algorithm is simple and easy to implement, and the wall structure
we get from the tiles allows to achieve visuals that reproduce all the small
details of artist painted walls.
