随机选择一个分支执行。
stochastic({ weight: Rule }*)
stochastic { weight: Rule }*
@StartRule
Lot --> primitiveCube(6, 4, 0.2)
extrude(5)
comp(f) { top: Roof | side: Wall }
Roof --> color(0.5, 0.25, 0.15)
Wall -->
stochastic(
30% : color(0.8, 0.2, 0.2)
30% : color(0.2, 0.8, 0.2)
40% : color(0.2, 0.2, 0.8)
)