Pushing animation frames to the view

[apcode]

I have an application where I am continually calculating data and I want to have the view display this as it happens in an animation.

As a simple example below, I tried rotating a cylinder (instead of streaming new data).
The cylinder (data) is updated in the background and I would like the view to display this as it happens.

Here is my example code to demonstrate the kind of thing I would like. But it gives the error about the event loop shown at the bottom of this post.

Is this possible with trame and if so how? Thanks.

import threading
import time

import pyvista as pv

from pyvista.trame.ui import plotter_ui
from trame.app import get_server
from trame.ui.vuetify import SinglePageLayout


pv.OFF_SCREEN = True


server = get_server()
state, ctrl = server.state, server.controller


cyl = pv.Cylinder(resolution=8, direction=(0, 1, 0))

pl = pv.Plotter()
pl.background_color = (0.1, 0.2, 0.4)
pl.add_mesh(cyl, name="cyl")


def _update(cyl, plotter, ctrl):
    print("sleep")
    time.sleep(5)
    for step in range(50):
        print(f"update {step}")
        cyl.rotate_x(10.0, inplace=True)
        cyl.rotate_y(-5.0, inplace=True)
        plotter.add_mesh(cyl, name="cyl")
        plotter.render()
        ctrl.view_update()
        time.sleep(0.5)


with SinglePageLayout(server) as layout:
    with layout.content:
        view = plotter_ui(pl)
        ctrl.view_update = view.update


thread = threading.Thread(target=_update, args=(cyl, pl, ctrl))
thread.daemon = True
print("Starting thread...")
thread.start()

print("Starting server...")
server.start()

Exception in thread Thread-1 (_update):
Traceback (most recent call last):
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
    self.run()
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/threading.py", line 953, in run
    self._target(*self._args, **self._kwargs)
  File "/home/alan/Workspace/apcode/newey/lightning/streamline/demo-trame.py", line 34, in _update
    ctrl.view_update()
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_server/controller.py", line 277, in __call__
    result = f(*args, **kwargs)
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_vtk/widgets/vtk/common.py", line 550, in update
    self.update_image(reset_camera)
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_vtk/widgets/vtk/common.py", line 539, in update_image
    MODULE.push_image(self.__view, reset_camera)
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_vtk/modules/vtk/__init__.py", line 240, in push_image
    return HELPER.push_image(render_window, reset_camera)
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_vtk/modules/vtk/__init__.py", line 94, in push_image
    return self._trame_server.protocol_call(
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_server/core.py", line 430, in protocol_call
    return func(obj, *args, **kwargs)
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_vtk/modules/vtk/protocols/publish_image_delivery.py", line 146, in image_push
    self.push_render(real_view_id)
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/trame_vtk/modules/vtk/protocols/publish_image_delivery.py", line 67, in push_render
    schedule_callback(
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/site-packages/wslink/__init__.py", line 52, in schedule_callback
    loop = asyncio.get_event_loop()
  File "/home/alan/anaconda3/envs/ptg/lib/python3.10/asyncio/events.py", line 656, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
RuntimeError: There is no current event loop in thread 'Thread-1 (_update)'.

[jourdain]

The solution below is just using the async event loop. If you need a tread you need to sync the request with the event loop like we do here

import time
import asyncio

import pyvista as pv

from pyvista.trame.ui import plotter_ui
from trame.app import get_server
from trame.ui.vuetify import SinglePageLayout

pv.OFF_SCREEN = True

server = get_server()
state, ctrl = server.state, server.controller

cyl = pv.Cylinder(resolution=8, direction=(0, 1, 0))

pl = pv.Plotter()
pl.background_color = (0.1, 0.2, 0.4)
pl.add_mesh(cyl, name="cyl")

keep_rotate = True

@ctrl.add_task("on_server_ready")
async def _update(**kwargs):
    await asyncio.sleep(5)
    while keep_rotate:
        cyl.rotate_x(10.0, inplace=True)
        cyl.rotate_y(-5.0, inplace=True)
        pl.add_mesh(cyl, name="cyl")
        pl.render()
        ctrl.view_update()
        await asyncio.sleep(0.5)


with SinglePageLayout(server) as layout:
    with layout.content:
        view = plotter_ui(pl)
        ctrl.view_update = view.update

server.start()

I pushed that example here for reference.