Creating video with pygfx

I’m working on the sphinx gallery for the examples and I got the basic pieces working. At the moment we can generate a gallery and have sphinx-gallery use pygfx to render images and add them. Something like this:

There are a few more things to iron out (like giving each example a title so that sphinx can link it automatically), but the basics are there.

One thing that is, perhaps, a bit of a luxury, but is still really useful for us is to show videos/animations in the gallery. This essentially works by creating a GIF that gets shown instead of the usual PNG. For this I have two discussion points:

• Is there an existing example of capturing a video with pygfx?
• The code for the video may have to be partly embedded in the example (to say “take a picture here, but do a video for X seconds there”). From a pedagogical perspective, this is suboptimal because we would ideally like to just show the example with the usual run() call so that they can see it nicely once they copy the code. Would an alternative be to say “we always show 5 sec of video for each render”?

I’m not 100% clear yet on how I want to solve this problem, but if you have ideas, I’m all ears 😃

[FirefoxMetzger]

Using canvas.draw() does the trick. If we are not concerned about timings, we can do:

import pygfx as fx
import imageio.v3 as iio
from wgpu.gui.offscreen import WgpuCanvas


cube = fx.Mesh(
    fx.box_geometry(200, 200, 200),
    fx.MeshPhongMaterial(color="#336699"),
)

def animate():
    rot = fx.linalg.Quaternion().set_from_euler(fx.linalg.Euler(0.005, 0.01))
    cube.rotation.multiply(rot)

disp = fx.Display(WgpuCanvas())
disp.before_render = animate
disp.show(cube)

frames = []
n_frames = 3 * 25  # about 3 second GIF
for _ in range(n_frames):
    frames.append(disp.canvas.draw())

iio.imwrite("output.gif", frames, duration=40, loop=0)

This solves my issue. Closing!

[almarklein]

Another option could be to update the examples not to use the time, but assume that the fps is at 30 (which the GUI backends run at by default). Then we can just take screenshots (which may take much longer on lavapipe) and set the mp4/gif playback speed at 30 fps.