Hello everyone

I am pretty new to Maya and I wanted to start by making simple Minecraft models but I have a bit of a problem. My mental ray crashes every time I use it, so I have to stick to Maya Software.

When I want to smoothen the edges, I choose the object and press "3" on the keyboard -I don't know if this is the proper way to do it, but it works for me - but when I render it, the edges are sharp as original. This works with mental ray, I don't know why it doesn't.

I know it is probably something silly, but since I am new, I have no idea how to fix it

Thank you in advance!