Ignore points in the 3d window when using enable_point_picking

[p-j-smith]

Hi, the docs for enable_point_picking state that

The picked point can either be a point on the first intersecting mesh, or a point in the 3D window.

I know that I can set each mesh/point cloud to be pickable or not (using the pickable keyword of add_mesh), but I can't find a way of making the 3D window non-pickable. Is this something that is possible? Thanks!

[banesullivan]

At the moment this is not implemented and I don't think it is easily supported by VTK. AFIAK, the vtkPointPicker we are using doesn't have a way to turn this off easily. However, it's SetPickFromList method seems like a good start to better limit what is pickable.. I played with this and did get it to prevent picking in the window.

What we could do is implement an option in enable_point_picking() to prevent our internal picking callbacks unless an actor was picked. I was this would be easy but its proving actually kind of flaky/difficult to implement. Here is the diff if you want to pick up where I left off:

diff --git a/pyvista/plotting/picking.py b/pyvista/plotting/picking.py
index 54d90991..e09fcea1 100644
--- a/pyvista/plotting/picking.py
+++ b/pyvista/plotting/picking.py
@@ -230,7 +230,7 @@ class PickingHelper:
     def enable_point_picking(self, callback=None, show_message=True,
                              font_size=18, color='pink', point_size=10,
                              use_mesh=False, show_point=True, tolerance=0.025,
-                             **kwargs):
+                             limit_to_actors=False, **kwargs):
         """Enable picking at points.

         Enable picking a point at the mouse location in the render
@@ -276,6 +276,10 @@ class PickingHelper:
             is specified as fraction of rendering window
             size. Rendering window size is measured across diagonal.

+        limit_to_actors : bool, optional
+            When true, prevent picking points that do not intersect pickable
+            actors in the scene
+
         **kwargs : dict, optional
             All remaining keyword arguments are used to control how
             the picked point is interactively displayed.
@@ -286,6 +290,8 @@ class PickingHelper:
             self.picked_point = np.array(picker.GetPickPosition())
             self.picked_mesh = picker.GetDataSet()
             self.picked_point_id = picker.GetPointId()
+            if not self.picked_point_id >= 0 and limit_to_actors:
+                return
             if show_point:
                 self.add_mesh(self.picked_point, color=color,
                               point_size=point_size, name='_picked_point',

I got this to work reliably when paired with SetPickFromList but I can't think of a clean/inuitive way to couple SetPickFromList with the existing pickable option:

import pyvista as pv

p = pv.Plotter(notebook=0)

actor = p.add_mesh(pv.Sphere())
p.enable_point_picking(limit_to_actors=True)

picker = p.iren.get_picker()
picker.SetPickFromList(True)
picker.AddPickList(actor)

p.show()

[banesullivan]

I suppose we could have limit_to_actors be a list of actors to limit it to rather than a bool. Here would be the diff and an example:

diff --git a/pyvista/plotting/picking.py b/pyvista/plotting/picking.py
index 54d90991..c97bbbf2 100644
--- a/pyvista/plotting/picking.py
+++ b/pyvista/plotting/picking.py
@@ -230,7 +230,7 @@ class PickingHelper:
     def enable_point_picking(self, callback=None, show_message=True,
                              font_size=18, color='pink', point_size=10,
                              use_mesh=False, show_point=True, tolerance=0.025,
-                             **kwargs):
+                             limit_to_actors=None, **kwargs):
         """Enable picking at points.

         Enable picking a point at the mouse location in the render
@@ -276,6 +276,10 @@ class PickingHelper:
             is specified as fraction of rendering window
             size. Rendering window size is measured across diagonal.

+        limit_to_actors : list[vtkActor], optional
+            When true, prevent picking points that do not intersect these
+            actors in the scene.
+
         **kwargs : dict, optional
             All remaining keyword arguments are used to control how
             the picked point is interactively displayed.
@@ -286,6 +290,8 @@ class PickingHelper:
             self.picked_point = np.array(picker.GetPickPosition())
             self.picked_mesh = picker.GetDataSet()
             self.picked_point_id = picker.GetPointId()
+            if not self.picked_point_id >= 0 and limit_to_actors:
+                return
             if show_point:
                 self.add_mesh(self.picked_point, color=color,
                               point_size=point_size, name='_picked_point',
@@ -298,6 +304,10 @@ class PickingHelper:

         point_picker = _vtk.vtkPointPicker()
         point_picker.SetTolerance(tolerance)
+        if limit_to_actors:
+            point_picker.SetPickFromList(True)
+            for actor in limit_to_actors:
+                point_picker.AddPickList(actor)
         self.picker = point_picker
         point_picker.AddObserver(_vtk.vtkCommand.EndPickEvent, _end_pick_event)

import pyvista as pv

p = pv.Plotter(notebook=0)
actor = p.add_mesh(pv.Sphere())
p.enable_point_picking(limit_to_actors=[actor])
p.show()

[banesullivan]

Screen.Recording.2021-11-30.at.11.33.11.PM.mov

[p-j-smith]

That is very cool, thank you so much!

I think an easier way to have control over which actors are pickable might be to call SetPickable directly on the actor:

import pyvista as pv

p = pv.Plotter(notebook=0)

actor = p.add_mesh(pv.Sphere(), pickable=False)
p.enable_point_picking(limit_to_actors=True)

actor.SetPickable(True)
p.show()

This then decouples the enabling of point picking from selecting which actors are pickable. This would be useful for me in the app I'm developing that uses pyvistaqt - I can turn on point picking, then allow the user to select which actors are pickable/unpickable without needing to call disable_point_picking/enable_point_picking again.

Also, here are a couple of minor suggested changes to your implementation:

diff --git a/pyvista/plotting/picking.py b/pyvista/plotting/picking.py
index 54d90991..b757c176 100644
--- a/pyvista/plotting/picking.py
+++ b/pyvista/plotting/picking.py
@@ -230,7 +230,7 @@ class PickingHelper:
     def enable_point_picking(self, callback=None, show_message=True,
                              font_size=18, color='pink', point_size=10,
                              use_mesh=False, show_point=True, tolerance=0.025,
-                             **kwargs):
+                             pickable_window=False, **kwargs):
         """Enable picking at points.

         Enable picking a point at the mouse location in the render
@@ -276,6 +276,9 @@ class PickingHelper:
             is specified as fraction of rendering window
             size. Rendering window size is measured across diagonal.

+        pickable_window : bool, optional
+            When True, points in the 3D window are pickable. Default to True.
+
         **kwargs : dict, optional
             All remaining keyword arguments are used to control how
             the picked point is interactively displayed.
@@ -283,9 +286,14 @@ class PickingHelper:
         """

         def _end_pick_event(picker, event):
+
+            picked_point_id = picker.GetPointId()
+            if not pickable_window and not picked_point_id >= 0:
+                return
+
             self.picked_point = np.array(picker.GetPickPosition())
             self.picked_mesh = picker.GetDataSet()
-            self.picked_point_id = picker.GetPointId()
+            self.picked_point_id = picked_point_id
             if show_point:
                 self.add_mesh(self.picked_point, color=color,
                               point_size=point_size, name='_picked_point',

I thought pickable_window is a slightly more descriptive name for an argument than limit_to_actors. But perhaps I'm missing something here - are there other parts of the view that are being ignored apart from the window?

The checking of picked_point_id and pickable_window is done before assigning to self.picked_point etc. This way these attributes are not updated unless a valid point is picked.

I'll submit a PR as it might be easier to discuss the changes there.

Thanks again!