Problem with subdivision modeling outcome

So this is one of my first blender projects. I have a problem though.
When you increase the subdivision count some of the edges(the ones that aren’t “landlocked”) that were straight transform into a curve. I want some parts of the model to just have straight edges. How can I do this?
One more question. I want my mesh to have a smooth surface, but when you increase the subdivision count these crevices become apparent. they are really annoying and I don’t really know how to fix them. What should I do?

Have the mirror modifier above the subsurf modifier. Modifiers are applied from top to bottom, you want to subsurf the mirrored object not mirror a subsurfed object.

You can use edge creasing to control edges or use additional geometry. Read the blender manual
We no absolutely zero about the mesh of you model since you haven’t supplied a link to downlaod your .blend file.

If you see errors/artifacts in the mesh, turn off the subsurf and go and look at the mesh at those points

Yea, modeling questions usually require to see the mesh. The purpose of the model (still, animation, game, 3D print, other) is often important information also. Showing the references shouldn’t hurt either, if possible.

A lot of information is hidden in the file and easiest to share that is with the .blend like suggested above. Instructions on how to prepare a .blend for upload and how to upload is linked in my signature.

Ok, thanks, I will look into that.

stormtrooper helmet 3.blend (749 KB) heres the file.

heres the reference image. I have fixed some of the problems I had, but I just need some advice on shaping the mesh. I think some parts need to be more rounded. What should be my next step?

The way I built the example was

From top left:

  • cube
  • subdivide smooth
  • scaled and deleted extra
  • and shaped with proportional editing
  • inset and deleted faces
  • extrusion down, moving vertices, loop cuts
  • extrusion, moving vertices
  • extrusion, moving vertices

Added mirror modifier when it was time to start extruding edges and moving things around.

Thanks for the help, I will start over again and follow your example.

I am having a bit of trouble with the part where you inset the faces… everything else is working great though.

Nevermind I figured it out.

untitled.blend (731 KB)
Ok, I followed your directions as closely as I could and here is the result. But when I apply the subdivision modifier it goes a bit crazy. If you have any idea how I can fix that, thanks.

In edit mode “select all” then “remove doubles”

Yup, double geometry.

The structure is not very far from this

Thanks guys!