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When I print to a PDF using a PDF print driver, or even if I save using the native PDF export feature, I often get objects in model space that are faded. This looks very similar to the Faded Xref issue, but Xreffade is set to 0. The problem also appears when there are no xrefs. I don't have any locked layers in the file I just tested, in case faded locked layers may be the issue.
And while setting a viewport to LEGACY HIDDEN can stop the problem, another problem presents itself. The tessellation lines on curves on fillets are so dense, that the result is an extremely thick line.
I have corresponded with support on this, and most recently a week ago, without successful resolution. So, I am appealing to the minds here on the forum, in hopes you can resolve this. Note that I am on ver 14. I recall that a major reason for me to upgrade was in hopes of getting better quality PDF output, but this particular issue makes all that useless for many of my drawings.
Fade issues-Hidden and Legacy Hidden.dwg and PDF
This drawing above shows both situations, with both render styles. Also with the PDF printed to a PDF and also a version EXPORTED to a PDF.
Hidden render is NOT faded.dwg and PDF
This drawing shows an example where the HIDDEN shade style does NOT produce the faded output.