weird glass effect artifacts - Principled BSDF, Transmission 1 I'm a filmmaker and 2d motion designer that's starting his journey in 3d. Following blender guru tutorial I've encountered first major problem that I cannot overcome. I have those weird artifacts when try to apply glass shader onto the cup. The plate renders fine, but the cup has artifacts (it's the same material on a plate and on a cup.

Do you maybe have any ideas how to resolve this?
Nice cup! But it has 2 issues:

duplicated vertices
flipped normals

When you turn on Face Orientation in the overlays, you will see your cup is mostly red (flipped normals) and there is some flickering/pixel fight going on (duplicates).
To fix it select the cup, switch to edit mode, select all vertices with key A, then press M to open the merge context menu. There, select by distance to get rid of the duplicated vertices.
Then press SHIFT + N to recalculate the normals (outside).