Basic Trisurf Plot

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

Section

The plotly.js "Tri-Surf" examples use Mesh3d with parametric surfaces sampled as point clouds, then reconstructed using alphahull. Here we sample a hemisphere surface, pass the points to Mesh3d, and use alphahull: 0 (convex hull) to reconstruct the mesh. intensity: colors the surface by z-height.

alias Plotly.{Figure, Mesh3d}

# Sample hemisphere: theta [0, pi/2], phi [0, 2pi]
n_theta = 20
n_phi = 30

points = for i <- 0..(n_theta - 1), j <- 0..(n_phi - 1) do
  theta = i / (n_theta - 1) * :math.pi() / 2
  phi   = j / (n_phi - 1) * 2 * :math.pi()
  {:math.sin(theta) * :math.cos(phi),
   :math.sin(theta) * :math.sin(phi),
   :math.cos(theta)}
end

xs = Enum.map(points, &elem(&1, 0))
ys = Enum.map(points, &elem(&1, 1))
zs = Enum.map(points, &elem(&1, 2))

Figure.new()
|> Figure.add_trace(
  Mesh3d.new(
    x: xs,
    y: ys,
    z: zs,
    alphahull: 0,
    intensity: zs,
    colorscale: "Viridis",
    opacity: 0.9
  )
)
|> Figure.update_layout(
  title: "Basic Trisurf — Hemisphere",
  scene: %{
    xaxis: %{title: "X"},
    yaxis: %{title: "Y"},
    zaxis: %{title: "Z"}
  }
)
|> Plotly.show()