Create a polygonal plane

[Zcaic]

Hello：

  i want to plot a polygonal plane with some vertexs. For example, I have known five vertexs, I want to plot pentagon with the five vertexs, how can I plot it?
 Thanks!

[Alexboiboi]

Hi @Zcaic,

here one way to do this

import numpy as np
import plotly.graph_objects as go
from scipy.spatial import Delaunay
from scipy.spatial.transform import Rotation as R


def get_polygon_vertices(n=3, r=1, pos=(0.0, 0.0, 0.0), orient=None):
    """create regular polygon in the xy plane with `n` vertices"
    and radius `r` and position `pos=[x,y,z]`
    returns a (n,3) array of vertices"""
    t = np.linspace(0, 2 * np.pi, n, endpoint=False)
    x = r * np.cos(t)
    y = r * np.sin(t)
    z = np.zeros_like(x)

    res = np.array([x, y, z]).T
    if orient is not None:
        res = orient.apply(res)
    return res + np.array(pos)

def triangulate_3D(vertices):
    """Triangulate a polygon from its vertices in 3D"""
    eps = 1e-8 # after rotation vertices may not match exactly
    same = np.all(vertices - vertices[0]<eps, axis=0)
    proj_inds = [0, 1]
    if np.sum(same) == 1:
        proj_inds = np.where(same == False)[0]
    # triangulate projection
    tri = Delaunay(vertices[:, proj_inds])
    return tri.simplices


def create_polygon(n=3, r=1, pos=(0.0, 0.0, 0.0), orient=None):
    """create regular polygon in the xy plane with `n` vertices"
    and radius `r` and position `pos=[x,y,z]`
    returns a (n,3) array of vertices and (m,3) array of triangles indices"""
    # create polygon and triangulate it
    vertices = get_polygon_vertices(n, r, pos, orient)
    triangles = triangulate_3D(vertices)
    return vertices, triangles


def add_polygon(fig, polygon):
    """add triangulate polygon mesh to an existing figure"""
    vertices, triangles = polygon
    x, y, z = vertices.T
    i, j, k = triangles.T
    fig.add_mesh3d(x=x, y=y, z=z, i=i, j=j, k=k)


# create figure and add mesh3d object from vertices and triangles
fig = go.Figure(layout_scene_aspectmode="data")

for i in range(10):
    orient = R.from_euler('y', 90+10*i, degrees=True)
    polygon = create_polygon(n=i+3, r=1, pos=(i, 0, 0), orient=orient)
    add_polygon(fig, polygon)

fig.show()

By the way, github issues are more meant for bug reports and feature request. In the future I would kindly ask to to post this questions in the plotly forum.

You could then still post this one there and post the link to the topic here, so that I can answer it there.

Hope this helps ;)

[Zcaic]

Thank you very much！ It‘s perfect！

[alexcjohnson]

Thanks @Alexboiboi for the thoughtful solution and for the callout to https://community.plotly.com/ 🏆