Surface with opacity < 1 not showing

[stoiver]

@marcomusy nice package! Thanks.

I have just started to play with vedo, and would like to visualise some terrain with water over the top. I need to make the water transparent, so tried to use opacity = 0.5. But on my system this seems to completely make the layer disappear.

I tried one of your examples, examples/advanced/geological_model.py and have a screen dump below. I hope you can see that some of the data sets are missing (the ones which have an opacity set).

My system is from vedo --info is

_________________________________________________________________
vedo version      : 2022.2.3   https://vedo.embl.es
vtk version       : 9.1.0
python version    : 3.9.12 | packaged by conda-forge | (main, Mar 24 2022, 23:25:59) [GCC 10.3.0]
python interpreter: /home/anuga/miniforge3/envs/anuga39/bin/python
vedo installation : /home/anuga/miniforge3/envs/anuga39/lib/python3.9/site-packages/vedo
system            : Linux 5.4.72-microsoft-standard-WSL2 posix x86_64
monitor (primary) : default, resolution=(1368, 912), x=0, y=0

I use MobaXrerm as my XServer.

By the way I am also getting this warning/error

  File "/home/anuga/miniforge3/envs/anuga39/lib/python3.9/site-packages/vedo/plotter.py", line 3720, in _keypress
    elif "KP_" in key:  # change axes style
TypeError: argument of type 'NoneType' is not iterable

[marcomusy]

Hi Stephen, try with pip install vtk==9.0.3 (the latest vtk seems to have some problems with the rendering of transparent objects)

[stoiver]

Thanks @marcomusy, changed the version of vtk. Unfortunately still have the transparency problem. Just verify that vedo is now using vtk version 9.0.3. Here is the output from vedo --info

_________________________________________________________________
vedo version      : 2022.2.3   https://vedo.embl.es
vtk version       : 9.0.3
python version    : 3.9.12 | packaged by conda-forge | (main, Mar 24 2022, 23:25:59) [GCC 10.3.0]
python interpreter: /home/anuga/miniforge3/envs/anuga39/bin/python3.9
vedo installation : /home/anuga/miniforge3/envs/anuga39/lib/python3.9/site-packages/vedo
system            : Linux 5.4.72-microsoft-standard-WSL2 posix x86_64
monitor (primary) : default, resolution=(1368, 912), x=0, y=0

I had thought it might be my Xserver but I tried your napari example and the transparency is working. Below is the output from napari --info.

So I guess napari doesn't use vtk.

WARNING: QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-anuga'
WARNING:vispy:QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-anuga'
napari: 0.4.14
Platform: Linux-5.4.72-microsoft-standard-WSL2-x86_64-with-glibc2.31
System: Ubuntu 20.04.3 LTS
Python: 3.9.12 | packaged by conda-forge | (main, Mar 24 2022, 23:25:59)  [GCC 10.3.0]
Qt: 5.12.9
PyQt5: 5.12.3
NumPy: 1.21.6
SciPy: 1.8.0
Dask: 2022.05.2
VisPy: 0.10.0

OpenGL:
  - GL version:  3.1 Mesa 21.0.3
  - MAX_TEXTURE_SIZE: 16384

Screens:
  - screen 1: resolution 1368x912, scale 1.0

Plugins:
  - console: 0.0.4
  - scikit-image: 0.4.14
  - svg: 0.1.6

[marcomusy]

hi thanks for reporting, that is very strange.. can you reproduce this:

import vtk

source = vtk.vtkCubeSource()
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputConnection(source.GetOutputPort())
actor = vtk.vtkActor()
actor.SetMapper(mapper)

actor.GetProperty().SetOpacity(0.5)

renderer = vtk.vtkRenderer()
renderer.AddActor(actor)

renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)

iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renderWindow)
iren.Initialize()
renderer.ResetCamera()
iren.Start()

[stoiver]

@marcomusy, your simple vtk code works fine!

[marcomusy]

OK. What about this:

import vtk
import vedo 

actor = vedo.Cube().alpha(0.5)

renderer = vtk.vtkRenderer()
renderer.AddActor(actor)

renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)

iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renderWindow)
iren.Initialize()
renderer.ResetCamera()
iren.Start()

if so, what about

import vedo 
actor = vedo.Cube().alpha(0.5)
vedo.show(actor)

thanks for your patience :)

[stoiver]

@marcomusy both of your examples worked, but adding vedo.settings.useDepthPeeling = True caused the problem.

To be honest, I don't know what this line does!

So the following code doesn't display the cube.

import vedo 
vedo.settings.useDepthPeeling = True
actor = vedo.Cube().alpha(0.9)
vedo.show(actor)

[marcomusy]

i was suspecting that! this is what it does: https://en.wikipedia.org/wiki/Depth_peeling

It's probably a graphics card issue, but i'm not sure, I guess you can live without it?

[stoiver]

Yes I can definitely live without it!

Thanks for helping so much in tracking down the problem.

[fstrazzante]

@marcomusy Thank you for the amazing package! I had the same problem: whenever I tried to tune the opacity with the attribute "alpha", the object with alpha < 1 was transparent. I tried to add settings.useDepthPeeling = False but with no luck, the object was still transparent. I tried each example you posted and they all worked well. This was the code that didn't show the object two:

from vedo import *

settings.use_depth_peeling = False
one = Mesh("right-temporal.obj", c="green").alpha(1)
two = Mesh("right-zygomatic.obj", c="red").alpha(0.9)

plt = Plotter(bg='white').add_shadows()
plt.show(one, two)

Then I found this discussion on vtk forum and I saw that someone was speaking about shadows, so I tried to delete add_shadows() from Plotter and now the object shows up! I also tried to remove the add_depth_peeling = False and was still working. This is the final working code:

from vedo import *

one = Mesh("right-temporal.obj", c="green").alpha(1)
two = Mesh("right-zygomatic.obj", c="red").alpha(0.9)

plt = Plotter(bg='white')
plt.show(one, two)

I add the output of vedo --info

_________________________________________________________________
vedo version      : 2022.4.2   https://vedo.embl.es
vtk version       : 9.2.5
numpy version     : 1.22.4
python version    : 3.10.5 (tags/v3.10.5:f377153, Jun  6 2022, 16:14:13) [MSC v.1929 64 bit (AMD64)]
python interpreter: C:\Users\X\AppData\Local\Programs\Python\Python310\python.exe
vedo installation : C:\Users\X\AppData\Local\Programs\Python\Python310\lib\site-packages\vedo
system            : Windows 10 nt AMD64
monitor (primary) : \\.\DISPLAY1, resolution=(1920, 1200), x=0, y=0

If you need me to do any other test, let me know.

[marcomusy]

Hi Francesco, thanks for reporting this. Keep in mind that you can generate sort-of "fake" shadows to individual meshes which can be useful sometimes.

from vedo import *

one = Mesh(dataurl+"bunny.obj", c="green").alpha(1)
two = Mesh(dataurl+"bunny.obj", c="red").shift(0.4,0,0).alpha(0.9)

one.add_shadow("z", -0.1)
two.add_shadow("z", -0.1)

plt = Plotter(axes=1)
plt.show(one, two)
plt.close()