[vtkusers] vtkImageActor erases other actors?

[Andreas Pedroni]

Dear David  

Thank you very much for your answer. I tried your suggestions but unfortunately I did not lead to a solution to my problem.
It seems that only the ren.AddActor(plane_actor) has an effect on the rendered image. The ren.AddActor(spine_actor) is not shown. But when I comment out ren.AddActor(plane_actor) the spine_actor is shown.
It is also only a problem if I use a vtk.vtkImageActor(), which I have chosen as it is supposed to be more efficient(?) than doing it with a vtk.vtkPlaneSource().

Thanks again for helping!
Cheers
Andreas



> Am 18.11.2018 um 14:52 schrieb David Gobbi <david.gobbi at gmail.com>:
> 
> Hi Andreas,
> 
> Thanks for sending the code along with your question.  The method you want is AddViewProp(), but it's just a new name for AddActor() and it actually has the same behavior.
> 
> For the image actor, you probably want code like the following.
>   vtk_image = vtk.vtkImageData()
>    vtk_image.SetDimensions(720, 1280, 1)
>    vtk_image.SetSpacing(1.0, 1.0, 1.0)
>    vtk_image.SetOrigin(-(720 - 1)/2.0, -(1280 - 1)/2.0, 0.0)
> 
> The "Spacing" is the size of each pixel, and the "Origin" is the position of the first pixel in the image (in this case, I set it so that the center of the image will be at (0,0,0), I'm not sure if this is what you want but it is a good place to start).
> 
> After creating the image data, it is a good idea to add an assert to ensure the array is the correct size:
>   assert vtk_image.GetNumberOfPoints() == vtk_array.GetNumberOfTuples()
> 
> For the following code, I'm not sure what you are trying to do, but the effect will be to vertically squash the frame so that it is square:
>   plane_actor.SetScale(1, 0.5625, 1)
> 
> I hope this helps,
>   David
> 
> On Sun, Nov 18, 2018 at 4:43 AM Andreas Pedroni <anpedroni at gmail.com <mailto:anpedroni at gmail.com>> wrote:
> Dear list
> 
> I would like to display a 3D object in front of a vtkImageActor (using Python 3.6 and vtk on Mac OS, see code below). However, the vtkImageActor erases the 3D object. I read in the manual that one should use AddProp() with the renderer to add a vtkImageActor to a render scene. But there is no AddProp() method for the renderer class. I’d be very thankful for any suggestions. 
> 
> Best 
> Andreas 
> 
> 
> import vtk
> import cv2
> from vtk.util import numpy_support
> 
> IMAGEPATH = ‚/models3d/'
> VIDEOPATH = "20180816-133303.mp4“
> 
> def main():
>    cap = cv2.VideoCapture(VIDEOPATH)
>    success, frame = cap.read()
> 
>    frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
>    vtk_array = numpy_support.numpy_to_vtk(frame.reshape((-1, 3), order='F'), deep=False)
> 
>    # Create a vtkImage Object. This is filled with the vtkArray data later
>    vtk_image = vtk.vtkImageData()
>    vtk_image.SetDimensions(720, 1280, 1)
>    vtk_image.SetSpacing(720, 1280, 1)
>    vtk_image.SetOrigin(720, 1280, 0)
>    vtk_image.GetPointData().SetScalars(vtk_array)
>    # create the Texture for a plane
> 
>    # The Screen where the movie is mapped onto
>    plane = vtk.vtkPlaneSource()
> 
>    plane_mapper = vtk.vtkPolyDataMapper()
>    plane_mapper.SetInputConnection(plane.GetOutputPort())
> 
>    plane_actor = vtk.vtkImageActor()
>    plane_actor.SetInputData(vtk_image)
>    plane_actor.SetScale(1, 0.5625, 1)
>    plane_actor.SetOrientation(180, 180, 90)
> 
>    # add the spine object
>    obj_importer = vtk.vtkOBJReader()
>    obj_importer.SetFileName(IMAGEPATH + 'Spine.obj')
>    obj_importer.Update()
> 
>    spine_mapper = vtk.vtkPolyDataMapper()
>    spine_mapper.SetInputConnection(obj_importer.GetOutputPort())
> 
>    spine_actor = vtk.vtkActor()
>    spine_actor.SetMapper(spine_mapper)
>    spine_actor.SetOrientation(90, 10, 90)
>    spine_actor.SetScale(0.3, 0.3, 0.3)
> 
>    # set up the renderer and the window
>    ren = vtk.vtkRenderer()
>    ren_win = vtk.vtkRenderWindow()
>    ren_win.AddRenderer(ren)
>    ren_win.SetSize(1500, 1500)
> 
>    ren.AddActor(spine_actor)
>    ren.AddActor(plane_actor)
> 
>    ren.SetBackground(0, 0, 0.1)
> 
>    iren = vtk.vtkRenderWindowInteractor()
>    iren.SetRenderWindow(ren_win)
> 
>    # Initialize must be called prior to creating timer events.
>    iren.Initialize()
> 
>    # start the interaction and timer
>    iren.Start()
> 
> if __name__ == '__main__':
>    main()

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