Let's Learn Blender! #5: Smoothing & Hard Edges - YouTube
Subdivide — Blender Manual
Subdivision Surface Modifier — Blender Manual
subdivision surface - Unable to find "Subdivide Smooth" option in blender 2.8 - Blender Stack Exchange
Please help me, how can I smooth those lines? I thought that subdivision surface smooths those corners, but no :( I don't get the logic how some lines are smooth and some