Adding Contour Lines to 3D Plots

Question

I am working with the R programming language. I made the following 3 Dimensional Plot using the "plotly" library:

library(dplyr)
library(plotly)

  my_function <- function(x,y) {
    
    final_value = (1 - x)^2 + 100*((y - x^2)^2)
     
    }

input_1 <- seq(-1.5, 1.5,0.1)
input_2 <- seq(-1.5, 1.5,0.1)

z <- outer(input_1, input_2, my_function)

plot_ly(x = input_1, y = input_2, z = z) %>% add_surface()

I am now trying to add "contour lines" to the above plot as shown below: https://plotly.com/r/3d-surface-plots/

I am trying to adapt the code from the "plotly website" to make these contours, but I am not sure how to do this:

Graph 1:

# This might have worked?
fig <- plot_ly(z = ~z) %>% add_surface(
  contours = list(
    z = list(
      show=TRUE,
      usecolormap=TRUE,
      highlightcolor="#ff0000",
      project=list(z=TRUE)
      )
    )
  )
fig <- fig %>% layout(
    scene = list(
      camera=list(
        eye = list(x=1.87, y=0.88, z=-0.64)
        )
      )
  )

Graph 2:

# I don't think this worked?
fig <- plot_ly(
  type = 'surface',
  contours = list(
    x = list(show = TRUE, start = 1.5, end = 2, size = 0.04, color = 'white'),
    z = list(show = TRUE, start = 0.5, end = 0.8, size = 0.05)),
  x = ~x,
  y = ~y,
  z = ~z)
fig <- fig %>% layout(
    scene = list(
      xaxis = list(nticks = 20),
      zaxis = list(nticks = 4),
      camera = list(eye = list(x = 0, y = -1, z = 0.5)),
      aspectratio = list(x = .9, y = .8, z = 0.2)))

fig

Can someone please show me how to correctly adapt these above codes?

Answer 1

You were almost there.
The contours on z should be defined according to min-max values of z:

plot_ly(x = input_1, y = input_2, z = z,
        contours = list(
          z = list(show = TRUE, start = round(min(z),-2),
                                end = round(max(z),-2), 
                                size = 100))) %>% 
        add_surface()

or automatically set by plotly :

plot_ly(x = input_1, y = input_2, z = z,
        colors = 'Oranges',
        contours = list(
          z = list(show = TRUE))) %>% 
  add_surface()