I’m working on the helmet tutorial in the official documentation.
I have two different objects: the side and upper of the helmet, and the lower region.
I combined them using Mesh > Combine.
Then I select the border edges from the two objects by using the select border edge tool.
I select five border edges for each object like illustrated on the picture and I’m sure there is nothing else selected.
I go to Bridge tool and put 0 division, then try to bridge and I have this error:
“Error: Invalid selection : polyBridgeEdge requires equal number of border edges to be selected for source and target selection.”
I guess it means I have more or less edges selected on either the source or the target, but I’ve checked everywhere, I can’t see any another lost edge selected…
Is it a bug or my fault somewhere?

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The Bridge tool works fine, within the limits of its capability. But it is simply not as smart as you are, and can easily be confused about what is supposed to connect to what.

Bridging multiple edges can be tricky. Besides selection order, normal direction is used to match the surface front and back sides, which is needed so that the correct end of each edge is connected to the correct end of the other edge.

Try this in smaller bites. Pick two edges, I would recommend the middle two, and bridge those. If you get a surface that crosses over itself (sort of an X shape) then that would indicate that one part or another is inside-out. Selecting a group of faces and then Normals -> Reverse should fix that. In the Display menu you can turn backface culling on and off, with it on, faces will be invisible from the back side… not a good way to work but an excellent way to determine that you have your inside and outside portions correctly oriented.

But if that works right, just merge the rest in pairs. If you do that, you will probably need to select and merge (Edit Mesh -> Merge) pairs of edges, because Bridge does not merge the edges.

<* Wes *>

Hi Wesley, thanks for your help.
Actually I’ve just solved the problem before I read your post because I found another one dealing with the same issue.
As you said it’s a matter of normals. It took me a while before getting it but eventually I selected the lower region faces then reversed its normals, then bridged and it worked fine.
I’m going to send a comment to Autodesk about this section of tutorial because as we can see, it doesn’t work fine as they say.

Glad you got back on track.

I never actually did that tutorial, but learning to make things with the inside inside is an important step in your modeling education, an issue that is not confined to Maya modeling.

Having two-sided polygons as a default and backface-culling off makes it easy to miss the problem. Some other modeling programs paint backfaces black or just display them as invisible (as they would be in a game engine). But Maya and Max default to double-sided, fine for film, not so good for games.

<* Wes *>

I haven’t understood well the purpose of turning off backface culling. I see the difference in the panels but for example it doesn’t change the polycount, whether it’s on or off, nor the render because I can still see the inside of the helmet with backface culling turned off.