Legend is missing for type "mesh3d" unless some surface trace is added

Inizia riproducendo gli esempi mesh3d nell’issue e confronta il comportamento con l’issue 2642 e la pull request 4386 referenziati di plotly.js. Traccia il modo in cui plotly.R passa le trace mesh3d a plotly.js; il lavoro è completato quando una trace mesh3d mostra la propria legenda senza richiedere l’aggiunta di una trace surface.

plotly.js added support for more trace legends but, for mesh3d, there is no legend below unless showlegend = TRUE for the mesh and a surface is added.

GH issue for more trace legends
merge for above

library(plotly)
library(rmarchingcubes)

R <- 2
f1 <- function(x, y, z){
  x^2 + y^2 + z^2 - R^2
}
f2 <- function(x, y, z){
  (x-2)^2 + (y-2)^2 + (z-2)^2 - R^2
}
g <- function(x, y, z) {
  pmax(f1(x, y, z), f2(x, y, z))
}

n <- 100
x_ <- y_ <- z_ <- seq(-R, R, length.out = n) 
Grid <- expand.grid(X = x_, Y = y_, Z = z_)
voxel <- with(Grid, array(g(X, Y, Z), dim = c(n, n, n)))
surf <- contour3d(voxel, level = 0, x_, y_, z_)
vertices <- surf$vertices
indices  <- surf$triangles - 1L

plot_ly(
  x = vertices[, 1], y = vertices[, 2], z = vertices[, 3],
  i = indices[, 1], j = indices[, 2], k = indices[, 3],
  type = "mesh3d",
  name = "hello world",
  showlegend = TRUE
) %>% layout(scene = list(aspectmode = "data"))

z <- c(
  c(8.83,8.89,8.81,8.87,8.9,8.87),
  c(8.89,8.94,8.85,8.94,8.96,8.92),
  c(8.84,8.9,8.82,8.92,8.93,8.91),
  c(8.79,8.85,8.79,8.9,8.94,8.92),
  c(8.79,8.88,8.81,8.9,8.95,8.92),
  c(8.8,8.82,8.78,8.91,8.94,8.92),
  c(8.75,8.78,8.77,8.91,8.95,8.92),
  c(8.8,8.8,8.77,8.91,8.95,8.94),
  c(8.74,8.81,8.76,8.93,8.98,8.99),
  c(8.89,8.99,8.92,9.1,9.13,9.11),
  c(8.97,8.97,8.91,9.09,9.11,9.11),
  c(9.04,9.08,9.05,9.25,9.28,9.27),
  c(9,9.01,9,9.2,9.23,9.2),
  c(8.99,8.99,8.98,9.18,9.2,9.19),
  c(8.93,8.97,8.97,9.18,9.2,9.18)
)
dim(z) <- c(15,6)

plot_ly(
  x = vertices[, 1], y = vertices[, 2], z = vertices[, 3],
  i = indices[, 1], j = indices[, 2], k = indices[, 3],
  type = "mesh3d",
  name = "hello",
  showscale = FALSE,
  showlegend = TRUE
) %>% 
  plotly::layout(scene = list(aspectmode = "data")) %>% 
  add_surface(z = ~z, name = "placeholder")