cafewall illusion in R

animation.r

library(animation)
ani.options(outdir = getwd())
saveGIF({
  ani.options(interval = 1)
  grid.newpage()
  rs <- expand.grid(x = seq(0, 1, 1/10), y = seq(0, 1, 1/10))
  grid.rect(rs$x, rs$y, 1/10/2, 1/10/2, gp = gpar(fill = "black", col = NA))
  grid.rect(rs$x + 1/10/4, rs$y + 1/10/2, 1/10/2, 1/10/2, gp = gpar(fill = "black", col = NA))
  ls <- expand.grid(x = 0:1, y = seq(0, 1, 1/20) - 1/20/2)
  grid.polyline(ls$x, ls$y, id = gl(nrow(ls)/2, 2), gp = gpar(col = "grey50", lwd = 1))
  grid.newpage()
  ls <- expand.grid(x = 0:1, y = seq(0, 1, 1/20) - 1/20/2)
  grid.polyline(ls$x, ls$y, id = gl(nrow(ls)/2, 2), gp = gpar(col = "grey50", lwd = 1))
}, movie.name = "cafewall.gif")

colored.r

# random color version

grid.newpage()
rs <- expand.grid(x = seq(0, 1, 1/10), y = seq(0, 1, 1/10))
grid.rect(rs$x, rs$y, 1/10/2, 1/10/2, gp = gpar(fill = rgb(matrix(runif(3 * nrow(rs)), nrow(rs))), col = NA))
grid.rect(rs$x + 1/10/4, rs$y + 1/10/2, 1/10/2, 1/10/2, gp = gpar(fill = rgb(matrix(runif(3 * nrow(rs)), nrow(rs))), col = NA))
ls <- expand.grid(x = 0:1, y = seq(0, 1, 1/20) - 1/20/2)
grid.polyline(ls$x, ls$y, id = gl(nrow(ls)/2, 2), gp = gpar(col = "grey50", lwd = 1))

plain.r

library(grid)
grid.newpage()
rs <- expand.grid(x = seq(0, 1, 1/10), y = seq(0, 1, 1/10))
grid.rect(rs$x, rs$y, 1/10/2, 1/10/2, gp = gpar(fill = "black", col = NA))
grid.rect(rs$x + 1/10/4, rs$y + 1/10/2, 1/10/2, 1/10/2, gp = gpar(fill = "black", col = NA))
ls <- expand.grid(x = 0:1, y = seq(0, 1, 1/20) - 1/20/2)
grid.polyline(ls$x, ls$y, id = gl(nrow(ls)/2, 2), gp = gpar(col = "grey50", lwd = 1))