Reproducible Example of Curvature Blindness Illusion

BCI.R

# Reproducible Example of
# Curvature Blindness Illusion
# Kohske Takahashi, Chukyo University, Japan
# ref: http://journals.sagepub.com/doi/abs/10.1177/2041669517742178

library(grid)
grid.newpage()

# some params
NY = 48
height = 0.75
xd = 20
col1 = "gray70"
col2 = "gray30"

N = 500
x = seq(0, 1, length.out = N)
ys = (0:NY/NY)[rep(c(F,T,T,F), length.out=NY)]
di = rep(c(1,1,-1,-1), length.out = NY)

bd = 0.5
grid.rect(gp = gpar(fill = "gray50"))
grid.polygon(c(0, bd, 0), c(1, 1, 1-bd), gp = gpar(col=NA,fill = "white"))
grid.polygon(c(1-bd, 1, 1), c(0, bd, 0), gp = gpar(col=NA,fill = "black"))


for (i in 1:length(ys)) {
  # all lines are sine wave!!
  y = (sin(20*x*pi)+1)/100*height + ys[i]
  
  id = di[i]*sin(40*(x)*pi)>0
  id = cumsum(c(0, diff(id)) > 0)
  id[id%%2==0] = NA
  grid.lines(x, y, gp = gpar(col = col1, lwd = 3))
  grid.polyline(x, y, id = id, gp = gpar(col = col2, lwd = 3))
}