Render issues with subdivision surface The issue is I modeled a coffee mug, and I did several renders of it with different colors. But at a certain point it started rendering as though the subdivision surface modifier wasn't there.

For the time being I found that if I set the viewport value to 6 it renders alright. But if I set it to a lower value it looks pretty horrible and square.

Working like this is tedious because I set the viewport value to 1 to make the computer go faster while I am making some changes to my design, and then I forget to reset it to 6. Then I find myself swearing my head off to the ceiling as after 20 minutes of rendering I have to start over again. And my computer isn't terribly quick, which doesn't help.

I hope someone can help me out and explain why this is happening to me, and what I need to do in order to fix it. I am a complete novice in blender and for the moment I am completely clueless.
Best to post a screenshot of your mesh and the modifier.

Check the image attached to make sure the camera icon on your modifier is on.