[vtkusers] Dealing with QTBUG-40889

[Elvis Stansvik]

2016-07-02 14:03 GMT+02:00 David Gobbi <david.gobbi at gmail.com>:

> On Sat, Jul 2, 2016 at 4:12 AM, Elvis Stansvik <
> elvis.stansvik at orexplore.com> wrote:
>
>>
>>> However, since VTK no longer renders for every input event, I have to be
>>> careful when I use the VTK picker.  I wrote a method called
>>> UpdatePropsForPick() that I call for every input event, and it ensures that
>>> the picking works correctly regardless of whether the Render()s are
>>> actually happening.
>>>
>>
>> Ah, this is good advice. Would you mind sharing how it ensures this? Not
>> necessarily in code, but just in a few words? I'm quite new to VTK and
>> haven't done any picking yet.
>>
>
> Here's the code.  It is only for pickers derived from vtkPicker (I use it
> with vtkCellPicker).  Pickers derived from vtkPicker work by interrogating
> the data, i.e. they don't use OpenGL for the picking.  Perhaps I should
> contribute this to VTK as a vtkPicker method.
>

Thanks a lot for this snippet. I'll get back to it should I need to do any
picking (I expect I will).

Elvis


> void UpdatePropsForPick(vtkPicker *picker, vtkRenderer *renderer)
> {
>   // Go through all Prop3Ds that might be picked and update their data.
>   // This is necessary if any data has changed since the last render.
>   vtkPropCollection *props;
>   if (picker->GetPickFromList()) {
>     props = picker->GetPickList();
>   }
>   else {
>     props = renderer->GetViewProps();
>   }
>
>   vtkProp *prop;
>   vtkCollectionSimpleIterator pit;
>   props->InitTraversal(pit);
>   while ((prop = props->GetNextProp(pit)) != 0) {
>     if (!prop->GetPickable() || !prop->GetVisibility()) {
>       continue;
>     }
>     vtkAssemblyPath *path;
>     prop->InitPathTraversal();
>     while ((path = prop->GetNextPath()) != 0) {
>       vtkProp *anyProp = path->GetLastNode()->GetViewProp();
>
>       vtkActor *actor;
>       vtkVolume *volume;
>       vtkImageSlice *imageActor;
>
>       if ((actor = vtkActor::SafeDownCast(anyProp)) != 0) {
>         actor->GetMapper()->Update();
>       }
>       else if ((volume = vtkVolume::SafeDownCast(anyProp)) != 0) {
>         volume->GetMapper()->Update();
>       }
>       else if ((imageActor = vtkImageSlice::SafeDownCast(anyProp)) != 0) {
>         imageActor->GetMapper()->Update();
>       }
>     }
>   }
> }
>
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