I have a cube and I’d like to make the top smoother without just puting a sphere on it.

Something like this :

“Question” is not a meaningful header. Nearly everbody posting here has a question. :wink:

You could subdivide the top face of the cube two or three times, select the vertex in the middle, and use proportional vertex editing (O-key; Shift+O to toggle between sharp and smooth, + and - buttons on the NumPad to increase or decrease the sphere of influence)

The best way I find, is to subdivide the entire cube about 3 times.

You can do it quickly by pressing

Then press the Tab key twice

Then select all vertices on the top of your cube and in the Edit Buttoms (F9) click Select Swap and then Hide.

You should now be left with just the top face of your Cube.

Then select the middle Vertice of the Top Face, press the O Key to get into proportional editing. Now from a Side view num_pad 1 or 3 press the G Key to move the vertice and distort the surrounding vertices accordingly.

For the dome effect that you’re looking for, I would suggest the Smooth FallOff option. Remember by pressing + or - buttons on the num_pad will adjust the digree of influence that the centre vertice has on the rest of the face.

Hope this is of use to you