3D Mesh Cube

Mix.install([
  {:plotly_ex, "~> 0.3"},
  {:kino, "~> 0.18"}
])

Section

A cube has 8 vertices and 6 faces. Each rectangular face is split into 2 triangles, giving 12 triangular faces total. facecolor: accepts a list of 12 CSS color strings — one per triangle — for per-face coloring. This is the Mesh3d equivalent of painting each face of a cube a different color.

alias Plotly.{Figure, Mesh3d}

# 8 vertices of a unit cube
x = [0, 0, 1, 1, 0, 0, 1, 1]
y = [0, 1, 1, 0, 0, 1, 1, 0]
z = [0, 0, 0, 0, 1, 1, 1, 1]

# 12 triangular faces (each cube face = 2 triangles)
# bottom: 0,1,2,3  top: 4,5,6,7  front: 0,3,7,4  back: 1,2,6,5  left: 0,1,5,4  right: 3,2,6,7
i = [0, 0, 4, 4, 0, 0, 1, 1, 0, 0, 3, 3]
j = [1, 2, 5, 6, 3, 7, 2, 6, 1, 5, 2, 6]
k = [2, 3, 6, 7, 7, 4, 6, 5, 5, 4, 6, 7]

# 2 triangles per face, 6 faces → pair up colors
face_colors = List.flatten(List.duplicate(
  ["red", "red", "blue", "blue", "green", "green",
   "yellow", "yellow", "cyan", "cyan", "magenta", "magenta"], 1))

Figure.new()
|> Figure.add_trace(
  Mesh3d.new(
    x: x, y: y, z: z,
    i: i, j: j, k: k,
    facecolor: face_colors,
    opacity: 0.8
  )
)
|> Figure.update_layout(
  title: "3D Mesh Cube — Per-Face Colors",
  scene: %{
    xaxis: %{title: "X"},
    yaxis: %{title: "Y"},
    zaxis: %{title: "Z"}
  }
)
|> Plotly.show()