CreateSandInAreaRand(<-area <-sandDef <-probability)
Creates sand of sandDef type in the area. Area is a V4 that specifies the lower left and upper right coordinates of a region. Probability is a float in the range of 0 to 1 indicating the probability of any cell in the area being filled with sand.
CreateSandInAreaRand(V4(0 0 512 512) 1 0.25) #Replaces approximately one in four pixels of sand in the entire map with stone