VtkLocalView.reset_camera with dynamic polydata

[PaulHax]

In my app with VtkLocalView, after modifying a polydata, the code calls html_view.update and html_view.reset_camera. However the rendered image does not fit the updated actor.

I though it has something to do with client getting the reset_camera command before updated scene like in this question: #316 However I'm not sure how to wait programmatically for that update without await asyncio.sleep hack.

Motivated by this project: https://github.com/PaulHax/burnoutweb/blob/threed/app/burn_out/app/world_view.py

I modifed the simple cone LocalRendering.py example that reproduces my approach and issue:
https://github.com/Kitware/trame/blob/master/examples/06_vtk/01_SimpleCone/LocalRendering.py
This code changes a polydata on the resolution state change.

How to change a polydata (or similar?) then have the client side camera fit the larger/smaller scene?

r"""
Version for trame 1.x - https://github.com/Kitware/trame/blob/release-v1/examples/VTK/SimpleCone/LocalRendering.py
Delta v1..v2          - https://github.com/Kitware/trame/commit/674f72774228bbcab5689417c1c5642230b1eab8

Installation requirements:
    pip install trame trame-vuetify trame-vtk
"""

from vtkmodules.vtkFiltersSources import vtkConeSource
from vtkmodules.vtkInteractionStyle import vtkInteractorStyleSwitch  # noqa
from vtkmodules.vtkRenderingCore import (
    vtkActor,
    vtkPolyDataMapper,
    vtkRenderer,
    vtkRenderWindow,
    vtkRenderWindowInteractor,
)
from vtkmodules.vtkCommonDataModel import vtkPolyData, vtkCellArray
from vtkmodules.vtkCommonCore import vtkPoints

from trame.app import get_server, asynchronous
from trame.ui.vuetify import SinglePageLayout
from trame.widgets import vtk as vtk_widgets
from trame.widgets import vuetify

# -----------------------------------------------------------------------------
# Trame initialization
# -----------------------------------------------------------------------------

server = get_server(client_type="vue2")
state, ctrl = server.state, server.controller

state.trame__title = "VTK Remote View - Local Rendering"

# -----------------------------------------------------------------------------
# VTK pipeline
# -----------------------------------------------------------------------------

DEFAULT_RESOLUTION = 6

renderer = vtkRenderer()
renderWindow = vtkRenderWindow()
renderWindow.AddRenderer(renderer)

renderWindowInteractor = vtkRenderWindowInteractor()
renderWindowInteractor.SetRenderWindow(renderWindow)
renderWindowInteractor.GetInteractorStyle().SetCurrentStyleToTrackballCamera()

# cone_source = vtkConeSource()
point_data = []
points = vtkPoints()
lines = vtkCellArray()

poly_data = vtkPolyData()
poly_data.SetPoints(points)
poly_data.SetLines(lines)

mapper = vtkPolyDataMapper()
actor = vtkActor()
# mapper.SetInputConnection(cone_source.GetOutputPort())
mapper.SetInputData(poly_data)
actor.SetMapper(mapper)
renderer.AddActor(actor)
renderer.ResetCamera()
renderWindow.Render()


def update_points(points, lines, point_data):
    point_ids = []
    for point in point_data:
        point_id = points.InsertNextPoint(point[0], point[1], point[2])
        point_ids.append(point_id)

    lines.InsertNextCell(len(point_ids))
    for point_id in point_ids:
        lines.InsertCellPoint(point_id)


# -----------------------------------------------------------------------------
# Callbacks
# -----------------------------------------------------------------------------


def update_rep(r):
    point_data = [(-r, -r, 0), (r, -r, 0), (r, r, 0), (-r, r, 0)]

    points = vtkPoints()
    lines = vtkCellArray()
    update_points(points, lines, point_data)

    poly_data.SetPoints(points)
    poly_data.SetLines(lines)
    poly_data.Modified()


async def async_flush():
    with state:
        ctrl.view_update()
    await server.network_completion
    ctrl.view_reset_camera()


@state.change("resolution")
def update_cone(resolution=DEFAULT_RESOLUTION, **kwargs):
    # cone_source.SetResolution(resolution)
    r = resolution
    update_rep(r)

    # ctrl.view_update()
    # ctrl.view_reset_camera()

    # not fitting new scene size either
    asynchronous.create_task(async_flush())


def update_reset_resolution():
    state.resolution = DEFAULT_RESOLUTION


# -----------------------------------------------------------------------------
# GUI
# -----------------------------------------------------------------------------

with SinglePageLayout(server) as layout:
    layout.icon.click = ctrl.view_reset_camera
    layout.title.set_text("Cone Application")

    with layout.toolbar:
        vuetify.VSpacer()
        vuetify.VSlider(
            v_model=("resolution", DEFAULT_RESOLUTION),
            min=3,
            max=60,
            step=1,
            hide_details=True,
            dense=True,
            style="max-width: 300px",
        )
        vuetify.VDivider(vertical=True, classes="mx-2")
        with vuetify.VBtn(icon=True, click=update_reset_resolution):
            vuetify.VIcon("mdi-undo-variant")

    with layout.content:
        with vuetify.VContainer(
            fluid=True,
            classes="pa-0 fill-height",
        ):
            view = vtk_widgets.VtkLocalView(renderWindow, ref="view")
            ctrl.view_update = view.update
            ctrl.view_reset_camera = view.reset_camera

# -----------------------------------------------------------------------------
# Jupyter
# -----------------------------------------------------------------------------


def show(**kwargs):
    from trame.app import jupyter

    jupyter.show(server, **kwargs)


# -----------------------------------------------------------------------------
# Main
# -----------------------------------------------------------------------------

if __name__ == "__main__":
    server.start()

[jourdain]

VtkLocalView has a on_ready event that you can listen to to see when reset_camera should be called.

Here is a gist of what you could do

def update_data(self):
    # ... update pipeline/data
    self.html_view.update()
    self.schedule_reset_camera = self.state.update_count + 1

@change("update_count")
def _on_update_count(self, update_count, **_):
    if update_count == self.schedule_reset_camera:
       self.html_view.reset_camera()

def _build_ui(self):
     with layout:
         # ...
         self.html_view = vtk_widgets.VtkLocalView(
              renderWindow,
              on_ready="update_count++",
         )

Another approach is to reset the camera on the server side (as you have the proper bounds) and call push_camera .

[PaulHax]

I went with VtkLocalView.push_camera. Thank you!