Combining enable_trackball_style and enable_trackball_actor_style to create a small 3D editor

[HLFILIOZAT]

Describe something you've made

I would like to create a small 3D editor, which means:

• given a scene composed of several actors,
• provide a user interface allowing:
  . to observe it (as usual)
  . AND also to transform it, by moving or resizing any of the included actors.

To my knowledge, this is not possible with a single interaction style of the current pyvista API.

For now, we have to “cumulate” 2 interaction styles, one to control the camera and the other one to control actors.
I have chosen:

• to control the camera: enable_trackball_style()
• to control an actor: enable_trackball_actor_style()

Links to Documentation, Examples, or Class Definitions.

https://docs.pyvista.org/version/stable/api/plotting/_autosummary/pyvista.Plotter.enable_trackball_style.html#pyvista-plotter-enable-trackball-style
https://docs.pyvista.org/version/stable/api/plotting/_autosummary/pyvista.Plotter.enable_trackball_actor_style.html#pyvista-plotter-enable-trackball-actor-style

Pseudocode or Screenshots

No response

[HLFILIOZAT]

First try with key events 'a' and 'c'.

import pyvista

pyvista.set_plot_theme( 'dark' )
plotter = pyvista.Plotter( notebook=False )

# gen the scene: 2 3D texts
txt1, txt2 = ("YES", "NO")
mesh = pyvista.Text3D( txt1, normal=(1,0,0), center=(5,0,0) )
plotter.add_mesh( mesh, name=txt1 )
mesh = pyvista.Text3D( txt2,  normal=(0,1,0), center=(0,5,0) )
plotter.add_mesh( mesh, name=txt2 )
# horizontal floor
plotter.add_floor( face='-z', show_edges=True, offset=0.1, pickable=False )
#
plotter.show_axes( )
#

def set_mode_camera_cb( ):
    plotter.enable_trackball_style()

def set_mode_actor_cb( ):
    plotter.enable_trackball_actor_style()

plotter.iren.add_key_event( 'a', set_mode_actor_cb )
plotter.iren.add_key_event( 'c', set_mode_camera_cb )

#
plotter.show( title='3D editor', full_screen=True )

[HLFILIOZAT]

Suitable but improvable, because the user does not know which mode he is interacting with.
I chose to show it by a text on the upper edge.

def set_mode_camera_cb( ):
    plotter.add_text( text='CAMERA', name='interaction mode', position='upper_edge' )
    plotter.enable_trackball_style()

def set_mode_actor_cb( ):
    plotter.add_text( text='ACTOR',  name='interaction mode', position='upper_edge' )
    plotter.enable_trackball_actor_style()

What could be better:

• merge all interactions into a single style:
  if the interaction starts "over" an actor -> transform the pointed actor,
  otherwise, drive the camera.
  This will make keyboard events useless.
• highlight the actor when hovering over it, before clicking on it !
• add some boolean properties to actors in order to authorize or prohibit its transformations:
  movable, orientable, resizable (on the model of the pickable property)
• help alignments

[HLFILIOZAT]

While testing this code, I would like to :

1. suggest an improvement to the pyvista API documentation:

• use of the term 'zoom':
  . reserve it for the opening / closing of the view angle (triggered exclusively by the 'up' or 'down' arrow keys)
  . applying to the camera: replace it with: moving the camera closer to or further away from the scene, along the focal axis
  . applying to actor: replace it with resizing the actor

2. notify an undocumented interaction in the trackball_actor mode:
   [CTRL] + middle mouse button makes the actor translate along an axis that I can't identify.

[HLFILIOZAT]

Finally, I have succeeded in implementing hovering, thanks to #4781

ADD the following code to the previous one (that initializes the plotter, creates the scene...) !

from vtkmodules.vtkCommonCore import vtkCommand
from vtkmodules.vtkInteractionWidgets import vtkHoverWidget
from vtkmodules.vtkRenderingCore import vtkPointPicker
picker = vtkPointPicker()

hovered_actor = None
def release_hovered_actor():
    global hovered_actor
    if hovered_actor is None:
        pass
    else:
        hovered_actor.prop.show_edges = False;
        hovered_actor = None
    return

def hovering_cb(_widget, event_name):
    x, y = plotter.iren.interactor.GetEventPosition()
    renderer = plotter.iren.get_poked_renderer(x, y)
    picker.Pick(x, y, 0, renderer)
    actors = list(picker.GetActors()) # /!\ generator !
    n_actors = len(actors)
    global hovered_actor
    if n_actors == 1:
        if hovered_actor == actors[0]: return # no change
        release_hovered_actor() # release previously hovered actor
        hovered_actor = actors[0]
        hovered_actor.prop.show_edges = True
        text = hovered_actor.name
        set_mode_actor_cb()
    elif n_actors == 0:
        text = ''
        if hovered_actor != None: release_hovered_actor()
        set_mode_camera_cb()
    else:
        text = f"{n_actors} actors / abort"
        set_mode_camera_cb()
    plotter.add_text( text=text,  name='hovering', position='upper_left' )

hw = vtkHoverWidget()
hw.SetInteractor(plotter.iren.interactor)
hw.SetTimerDuration(10)
hw.AddObserver(vtkCommand.TimerEvent, hovering_cb )
#hw.AddObserver(vtkCommand.EndInteractionEvent, hovering_cb)
hw.EnabledOn()