I tried many things to stop or understand this, without success:
use different skylight settings
disable skylight and only use ambient occlusion as lighting method
change camera lens length
change camera target location (although the camera always auto-adjusts, even with “auto adjust target depth” disabled
delete everything else in the file and only leave the empty room
give all objects in the scene the default Rhino material
use different PDF printers
use the “Rhino PDF” print option
The issue appears to be random in the sense that depending on the layout the bright lines sometimes appear in this detail view, sometimes in that. However the issue stays fixed for each layout, so the bright lines always appear in the same detail view on a given layout.
This looks like a bug with the skylight shadows print tiling at high DPI. I’ve filed this as https://mcneel.myjetbrains.com/youtrack/issue/RH-59989 for the developers to investigate. There were two workarounds I found if they help now. If I reduced the PDF print DPI to 175 the artifacts didn’t occur here. Or if I changed the model units to Meters and accepted the scaling of the model, that also prevented the issue but you lost your detail view placement with that one.
@cosmas I think this is related to what I was helping you with last week due to the DPI workaround. Although I couldn’t reproduce your issue that was a workaround you had discovered. You might look at file units too and hopefully any fix to this one would also address what you were seeing.
Unfortunately I could not get rid of the artifacts completely using the workarounds you described, but nearly.
Scale related changes at the stage of image export (PDF dpi, printer settings DPI or viewport capture scale) do have an influence, but for me it’s a bit inconsistent:
when I capture the viewport with the layout to a file (“capture” --> “file”) the artifacts are gone at lower resolutions (420x297 px and ‘scale’ less than- or equal to 4) and they appear at higher resolutions (‘scale’ above 4).
when I print to PDF the artifacts are very pronounced at 600 DPI and below but are very faint at 1000 DPI.
So it looks like I can work around the artifacts by exporting very high res PDF’s and then reducing them after.
Changing the model units to meters in addition to (and also independent of) the output resolution tweaks did not appear to make a difference in my case.
It feels like the artifacts may also be related to the fact that I am rendering inside a small enclosed space (i.e. that room). I set the lens length to ‘20’ to have more of the small space in the viewport. I think on default ‘50’ the artifacts are simply out of view.
The camera seems to be struggling with that situation in another aspect as well: it adjusts the target point in such a way that a kind of clipping plane (though not the actual camera far clipping plane) appears in the image, so that an area of non-rendered view creeps into the rendered view. The geometry is visible, but it does not have the AO shadowing any more. That’s why I added that large curve box around the actual model so that the camera has got some geometry in the distance to adjust to, thus keeping the room fully within the region of proper rendered appearance.
I’ll carry on with the situation as is, I hope my observations help you improve Rhino some more and I am looking forward to an update in which this may be fixed.
