vtkTextActor3D looks weird

I am using vtkTextActor3D to display 3D text, but it look weird.The code to reproduce my question is:

import vtkmodules.all as vtk

if __name__ == '__main__':

    line = vtk.vtkLineSource()
    line.SetPoint1(0, 0, 0)
    line.SetPoint2(1, 0, 0)

    mapper = vtk.vtkPolyDataMapper()
    actor = vtk.vtkActor()

    txt3D = vtk.vtkTextActor3D()
    txt3D.SetPosition(1, 0, 0)
    txt3D.GetTextProperty().SetColor(1, 0, 0)

    ren = vtk.vtkRenderer()
    renWin = vtk.vtkRenderWindow()
    iren = vtk.vtkRenderWindowInteractor()

The result is:

I can not figure out the 3D text in the above figure.
If I want to have a good 3D text, I need to give a larger font size:

txt3D.GetTextProperty().SetFontSize(20)   ########### modify: 2 to 20

And the result is:

The text is clear, but I almost can not see the line.

Is there any thing wrong with my code? How can I correctly display the 3D text.

I think the line must be resized accordingly:

    line = vtk.vtkLineSource()
    line.SetPoint1(0, 0, 0)
    line.SetPoint2(200, 0, 0)  ####old value (1, 0, 0)

It can make the result looks well.

But, I don’t want to change the position of the line. The position of (1, 0, 0) indicate a position in the real world, and the line has the reality meaning.

I want to display a 3D text for the line ( (0, 0, 0), (1, 0, 0) ). How to display the 3D text?

I find the vtkVectorText can also display 3D text, but I can not change the display preporty for it: color, font size, font family. In a world, vtkVectorText do not have vtkTextProperty.

vtkTextActor3D renders the text as a texture and the texture is applied to a rectangle. Being rendered as a texture means the text is rasterized according to the font settings. Setting its font size to 2, that would mean a very small text with very few pixels tall hence the bad results.

I’d keep the txt3D.GetTextProperty().SetFontSize(20) call, but I’d rescale the txt3D actor: txt3D.SetScale(0.1). You’ll likely need to add code to compute an adequate scale factor that will fit your (0,0,0)-(1,0,0) line. Either this or use another class to render your text without involving the use of textures.

1 Like

@Paulo_Carvalho Thank you for your kindly reply.

It is a good solution.

Is there any other class can render the 3D text?

vtkVectorText can be used to generate a vtkPolyData object from a string. You won’t have texture issues, but you’ll have a more computationally expensive scene. If you expect to have too many characters in your scene, vtkTextActor3D is a better choice.

I have tried vtkVectorText, but I can’t find how to set the font size, font family, line spacing and some properties which has been provided by vtkTextProperty. Can I use vtkTextProperty for vtkVectorText?

You can try the vtkCaptionActor2D class. Its setup is more complex than those of the other two classes, but it accepts a vtkTextProperty to configure font settings: https://vtk.org/doc/nightly/html/classvtkCaptionActor2D.html#details