Hello, I have issue, when I try rotate shape layer and enable 3d layer switch, my line becomes blurry, also I try use ai file and get same result (enable collapse transformations + 3d layer = blurry line), don't know how to fix this problem. Fun fact if I use ai file (with 100% scale) and enable only collapse transformations or 3d layer switch, no problem, but if turn on both, agai blurry line. I have latest After Effects 2021(18.0.1).
Do you have a camera in the comp? Is the depth of field enabled?
Have you tried a 1-pixel stroke viewed at 800%? There is a slight difference in antialiasing when you change to a 3D layer, and scaling up the layer even 1000% will only show a slight aliasing difference, but it would be completely different if continuous rasterization is turned off. By the way, you cannot turn Continuous rasterization off with shape layers or text layers.
Tried to create the same shapes and I've got the same result as yours, it's very subtle and I don't think the viewers will notice that unless it's used as a still picture, but yes there is a blurry edge for the 3d layer. It looks like a limitation in the Classic 3D render engine.
I tried Cinema 4D engine and blur gone, definitely restriction in Classic 3D engine.