--- author: Stéphane Laurent date: '2022-01-27' highlighter: 'pandoc-solarized' output: html_document: highlight: kate keep_md: no md_document: preserve_yaml: yes variant: markdown tags: 'graphics, python, pyvista' title: PyVista surface with dynamic colormap --- I've just done this animation with **PyVista**: ![](https://github.com/stla/PyVistaMiscellanous/raw/main/HopfTorusMovingFlag.gif) This is a Hopf torus with the so-called flag colormap as texture, but this texture moves. Here is a [link to the full code](https://github.com/stla/PyVistaMiscellanous/blob/main/HopfTorus_MovingFlag.py). The trick is to normalize the scalars to $[0, 2\pi]$ and then to apply the map $\sin(\cdot - t)$ to the scalars, with $t$ varying from $0$ to $2\pi$. Let me show you another example, with an ellipsoid.  {.python} from math import pi, sin import numpy as np import pyvista as pv mesh = pv.Sphere(theta_resolution=200, phi_resolution=200) mesh.scale((1, 0.5, 1), inplace=True) # ellipsoid dists = mesh.points[:,2] # we take the third coordinates for the scalars # then we map them to [0, 2*pi]: dists = 2*pi * (dists - dists.min()) / (dists.max() - dists.min()) t_ = np.linspace(0, 2*pi, 100, endpoint=False) # the varying parameter for i, t in enumerate(t_): pngfile = "pic%03d.png" % i pltr = pv.Plotter(window_size = [512, 256], off_screen = True) pltr.background_color = "#363940" pltr.set_focus([0, 0, 0]) pltr.set_position((1.3, 0, 0)) mesh["dist"] = np.sin(dists - t) # set the scalars - here is the "trick" pltr.add_mesh( mesh, smooth_shading = True, cmap = "flag", show_scalar_bar = False, specular = 10 ) pltr.show(screenshot = pngfile)  This code produces the png files pic000.png, ..., pic099.png. Then it remains to make a gif file from them, using e.g. **ImageMagick** or **gifski**. And here is the result: ![](figures/Ellipsoid_DynamicFlag.gif)