3d Mesh - Plotly Py — ContextQMD

Simple 3D Mesh example

go.Mesh3d draws a 3D set of triangles with vertices given by x, y and z. If only coordinates are given, an algorithm such as Delaunay triangulation is used to draw the triangles. Otherwise the triangles can be given using the i, j and k parameters (see examples below).

python

import plotly.graph_objects as go
import numpy as np

# Download data set from plotly repo
pts = np.loadtxt(np.DataSource().open('https://raw.githubusercontent.com/plotly/datasets/master/mesh_dataset.txt'))
x, y, z = pts.T

fig = go.Figure(data=[go.Mesh3d(x=x, y=y, z=z, color='lightpink', opacity=0.50)])
fig.show()

3D Mesh example with Alphahull

The alphahull parameter sets the shape of the mesh. If the value is -1 (default value) then Delaunay triangulation is used. If >0 then the alpha-shape algorithm is used. If 0, the convex hull is represented (resulting in a convex body).

python

import plotly.graph_objects as go
import numpy as np

pts = np.loadtxt(np.DataSource().open('https://raw.githubusercontent.com/plotly/datasets/master/mesh_dataset.txt'))
x, y, z = pts.T

fig = go.Figure(data=[go.Mesh3d(x=x, y=y, z=z,
                   alphahull=5,
                   opacity=0.4,
                   color='cyan')])
fig.show()

3D Mesh in Dash

Dash is the best way to build analytical apps in Python using Plotly figures. To run the app below, run pip install dash, click "Download" to get the code and run python app.py.

Get started with the official Dash docs and learn how to effortlessly style & publish apps like this with <a class="plotly-red" href="https://plotly.com/dash/">Dash Enterprise</a> or <a class="plotly-red" href="https://plotly.com/cloud/">Plotly Cloud</a>.

python

from IPython.display import IFrame
snippet_url = 'https://python-docs-dash-snippets.herokuapp.com/python-docs-dash-snippets/'
IFrame(snippet_url + '3d-mesh', width='100%', height=1200)

<div style="font-size: 0.9em;"><div style="width: calc(100% - 30px); box-shadow: none; border: thin solid rgb(229, 229, 229);"><div style="padding: 5px;"><div><p><strong>Sign up for Dash Club</strong> → Free cheat sheets plus updates from Chris Parmer and Adam Schroeder delivered to your inbox every two months. Includes tips and tricks, community apps, and deep dives into the Dash architecture. <u><a href="https://go.plotly.com/dash-club?utm_source=Dash+Club+2022&utm_medium=graphing_libraries&utm_content=inline">Join now</a></u>.</p></div></div></div></div>

Mesh Tetrahedron

In this example we use the i, j and k parameters to specify manually the geometry of the triangles of the mesh.

python

import plotly.graph_objects as go

fig = go.Figure(data=[
    go.Mesh3d(
        x=[0, 1, 2, 0],
        y=[0, 0, 1, 2],
        z=[0, 2, 0, 1],
        colorbar=dict(title=dict(text='z')),
        colorscale=[[0, 'gold'],
                    [0.5, 'mediumturquoise'],
                    [1, 'magenta']],
        # Intensity of each vertex, which will be interpolated and color-coded
        intensity=[0, 0.33, 0.66, 1],
        # i, j and k give the vertices of triangles
        # here we represent the 4 triangles of the tetrahedron surface
        i=[0, 0, 0, 1],
        j=[1, 2, 3, 2],
        k=[2, 3, 1, 3],
        name='y',
        showscale=True
    )
])

fig.show()

Mesh Cube

python

import plotly.graph_objects as go
import numpy as np

fig = go.Figure(data=[
    go.Mesh3d(
        # 8 vertices of a 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],
        colorbar=dict(title=dict(text='z')),
        colorscale=[[0, 'gold'],
                    [0.5, 'mediumturquoise'],
                    [1, 'magenta']],
        # Intensity of each vertex, which will be interpolated and color-coded
        intensity = np.linspace(0, 1, 8, endpoint=True),
        # i, j and k give the vertices of triangles
        i = [7, 0, 0, 0, 4, 4, 6, 6, 4, 0, 3, 2],
        j = [3, 4, 1, 2, 5, 6, 5, 2, 0, 1, 6, 3],
        k = [0, 7, 2, 3, 6, 7, 1, 1, 5, 5, 7, 6],
        name='y',
        showscale=True
    )
])

fig.show()

Intensity values defined on vertices or cells

The intensitymode attribute of go.Mesh3d can be set to vertex (default mode, in which case intensity values are interpolated between values defined on vertices), or to cell (value of the whole cell, no interpolation). Note that the intensity parameter should have the same length as the number of vertices or cells, depending on the intensitymode.

Whereas the previous example used the default intensitymode='vertex', we plot here the same mesh with intensitymode='cell'.

python

import plotly.graph_objects as go
import numpy as np

fig = go.Figure(data=[
    go.Mesh3d(
        # 8 vertices of a 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],
        colorbar=dict(title=dict(text='z')),
        colorscale=[[0, 'gold'],
                    [0.5, 'mediumturquoise'],
                    [1, 'magenta']],
        # Intensity of each vertex, which will be interpolated and color-coded
        intensity = np.linspace(0, 1, 12, endpoint=True),
        intensitymode='cell',
        # i, j and k give the vertices of triangles
        i = [7, 0, 0, 0, 4, 4, 6, 6, 4, 0, 3, 2],
        j = [3, 4, 1, 2, 5, 6, 5, 2, 0, 1, 6, 3],
        k = [0, 7, 2, 3, 6, 7, 1, 1, 5, 5, 7, 6],
        name='y',
        showscale=True
    )
])

fig.show()

Reference

See https://plotly.com/python/reference/mesh3d/ for more information and chart attribute options!