EDIT: I found that you can join them with the F key. It works great and I’ve already tested it, but I now have a different question. When I try to join some surfaces I get an error message saying “Cannot join interior surfaces.”. What does this mean?
Cant think of a time ive had that message, can you show a picture of what you are trying to join so the error can be replicated ?.
Let me explain a bit more, then. When I, let’s say, use the knife tool to cut a line and I want to merge polygons inside the cut/merge triangles to the existing polygon, how do I avoid an error message saying “cannot merge internal faces”? Does this mean that the polygons created with the tool cannot be merged with other ones?
Um, the F key is generally for making new faces, and the alt(i-think)-M key is about merging stuff together. . .
Not really sure what you mean otherwise, if you want to post a pic with the things you’re trying to work with selected it’d help alot :).
I was simply testing this method on the Natalie Portman object I made before with the tutorial. I’ll post a picture later.
I think I know what the message means. Just to ask, is a polygon required to be a certain size? Does Blender show me an error message if I try joining too many of them?
One more thing, I have used the merge tool before, but it’s unsatisfying as it often badly messes the mesh up.
S-Slash, the merge tool works as advertised. It makes two (or more) vertices into a single vertex, and gives several choices where you want that vertex located. Messy mesh merges generally occur because someone had vertices they didn’t want to merge selected. Like most software, Blender does what you tell it to do, which may not be what you want it to do. I’ve gotten into the habit of using a to deselect before I select stuff I want to merge. That way, the merge tool doesn’t pick up any “strays.”
Okay, here’s what the problem is:
I managed to word it incorrectly here, so my apologies for confusing anyone.
I can’t quite see a direct view but I’d make my guess at saying that there is at leat once vertex inside the face. you may want to make another screenshot with the message off to the side so we can see the mesh completely.
Difficult to see how many faces you have selected there, but i think your trying to make some kind of n-gon . you probably know already that blender does not support ngons ( polygons of more then 4 vertices).
I tried to press f with 4 poly selected next to each other, this brings up the make fgon message (fakeing a ngon it just hides the edge not a true ngon), i get your error message so you found a fake ngon that cant be made.
If i was you, i’d just stick to making 3 or 4 sided polygons.
The problem is the center vertice of your selection. The vertices have to be on the outside ring of the selection to make the F-Gon. I would agree with Hazza though on sticking with quad’s or tri’s.
A good description by LetterRip from another thread says it nicely:
The main difference between fgons and ngons is that ngons can have internal vertices and internal holes. Also fgons must have the faces that make up the fgon created before hand, whereas ngons will make the faces automatically. (both are composed of triangles internally, the ngons though hide the process from you…).
LetterRip
Also, If your using the subsurf modifier and the tri’s are not on a perfectly flat surface pinching and other artifacts will start to show up.
That’s exactly what I just tried as well. FGons can’t have a vertex inside of them, like when you make a cylinder and want to “join” all the faces of the cap to a fake-gon. It is not allowed.
I can only agree on Hazza’s suggestion and say: stick with normal polygons. FGons don’t really help you, they tend to hide unclean modeling and therefore are not a help but rather a problem. At least that’s my personal experience.
EDIT: Well, while I was checking that out with my Blender, someone posted before me… 
This could actually be the main reason for why I get the error. What I’m trying to do is to make several polygons into a single one, aka F-Gons, but the mesh prevents me from doing that. This is difficult because fixing triangles becomes harder. Should I simply remove a polygon, merge some vertices and try again?
Where can I find some information about productively controlling polygons and cleaning triangles and other mistakes in the mesh so I can get this to work?
To clean up triangles, the best way I’ve found, is to use edge looping on the base of the triangle and use the f key to turn the new vertex on the base of the triangle along with the original three into a new quad. You quickly end up with alot of new vertecies but I have yet to find a good alternative.
Okay, here’s the deal, the polygon I’m trying to merge does have four vertices, but the subsurf mode has curved the sides of the other one so it bends. Could this cause the error message? Should I remove the subsurf momentarily before trying again?
EDIT: Okay, I remembered your hint about polygons with three or four vertices and it works now like it should. Thanks.