Content behind window is visible

Support
1

Hi community,
I have a problem where the content behind VTK window is visible (showed in the attachments). I have two examples where this happened:

  1. I copied the first example of the VTK examples ([https://lorensen.github.io/VTKExamples/site/Python/GeometricObjects/CylinderExample/]) and the content behind the background is visible.

  2. The second example is a triangle with middle level of opacity in a white background. The content is visible behind the triangle. If the background is changed to any other color, the background also becomes translucent (can’t upload the code since I’m a new user but it is similar in structure to the Cylinder example but the actor has an opacity value).

At this point I do not know if I did something wrong or it’s something else. Any guidance will be helpful!
Thanks,
Ariel.

vtk_example vtk_triangle

2

This sounds like a driver issue of some kind. What video card and driver are you using (looks like Linux)?

@ken-martin

3

Hi Ben, Yes, it is Linux. The system is running on a VM so the video card and drivers are recognized for VM, but it was reproducible in other machines with Centos 7. BTW the problem happened with mesa 17 and 20.

4

This seems to be a Mesa/driver bug to me. Could to submit the information to the Mesa developers? I wonder if the VM is also doing weird things here. Feel free to link to it from here so others can follow along if they want.

FYI @Chuck_Atkins

5

This happens with x11 on Linux. The workaround: skip ARGB visuals,

export XLIB_SKIP_ARGB_VISUALS=1

But now, you won’t have alpha blending. A workaround: use a discrete GPU with drivers and avoid mesa. I’m not sure if there’s any other way around it other than hacking vtkXOpenGLRenderWindow somewhere around this line and here.

Check this for details if you choose to go down that road.

6

Could be an out-of-date Mesa as well (or a new bug I suppose!). I don’t think we’ve noticed it with 18.2.2, but that isn’t the newest release by a long shot.

7

Thanks for the workaround tips. I will evaluate if it is necessary to modify VTK. If I submit the information to Mesa devs, I will link it so other users can follow what is happening.
Thanks!