I have an image from a µCT I would like to render with paraview 5.9. To do that, I took the following Steps:
Load the .xmf image in paraview (the image is binary and contains only voxels with 0 or 1)
use the Threshold Filter with min=0.5 max=1 to only show voxels with a value >0
Select “Surface” as display type, and “Solid Color” for coloring
Click “Enable Ray Tracing” and “Shadows”, Set “Samples per Pixel” to 10
Now, in the renderview the image looks very good. But, if I save a screenshot, I get a lot of artifacts in the image. For example transparent pixels and lines going through the image:
So far I could track down where the artifacts come from:
The transparent pixels only occur, if I save the image with transparent backgrund
the lines only appear if I save the image in a different resolution than the one initially written in the screenshot dialog
Is there any possibility to prevent that and still save a screenshot with transparent background and high-resolution?
A workaround for the first issue is to save to a white background, then open the image in Photoshop and use the magic eraser tool. (There is probably a similar method for Gimp too…)
You mean “samples per pixel” in the render settings? Or the size of the screenshot?
If I create the screenshot, the “native” size is 1070x829. If I use that, I do not get the lines, but with transparent background I get the transparent pixels in the image. Using a screenshot size of 100x100 pixel also has no lines (at least none I can see with that reduced size) but with the transparent background I still have the pixels.
I also changed the samples per pixel to 100, but it gives the same result.
Thus, the only setting that does not produce any artifacts is native resolution with a colored background.
I tried to test PV5.11rc1 but unfortunately, our system is too old… We use CentOS 7.9 here, which has a too old libc. Maybe this is an issue also for pv 5.9?
The Hardware is a nvidia GTX 1050 Ti with driver 455.32.00.
okay, no, unfortunately that seems to not change it. I tried with 500 and there is no difference.
What makes a difference is, if I enter some arbitrary resolution or if I use the x2 button. It seems like, resolutions which are a multiple of the native one, work better. But there are still faint lines visible.
that’s not the first time the “Save screenshot” feature gives this kind of artefacts … we should really start to track them down because these are recurrently appearing on the discourse.
I’ll try to see if i can reproduce the issue today on the PV5.11rc1
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mwestphal
(Mathieu Westphal (Kitware))
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