# How can I fix the non-stitched seam that is present after applying mirror modifier?

I've followed the same tutorial I mentioned in the question I asked yesterday and my boat hull looks pretty good. The process is to make 3D B-Splines increase the resolution and then convert them to Mesh Elements. Then you make a plane and cut it in half along the "Y" axis.

I followed through the process and see a couple issues that I would like one of you to address. First, I see that the normals are not correct. The inside of the hull is not important but the outside needs to show materials. Also the hull is not stitched together along the keel. I don't know how to do that on a mesh that has had the Mirror Modifier applied to it.

Anyone care to help?

• You can recalculate the normals using Ctrl+N, and selecting Inside on the tool menu if the result is not what you want. As far as the stitching, select both edge loops and press S-Y-0 – VRM Apr 28 '15 at 15:32
• This site works best when asking one question at a time. I would suggest removing the normals part of the question and focus on the stitching of the hull. See if one of the questions already asked on the site answers the normals part. If not, ask another question. – Ray Mairlot Apr 28 '15 at 15:36

The normals issue can easily be solved by selecting all the vertices in edit mode and pressing Ctrl+N (You may need to select the Inside option as well, depending on your mesh). You could also add a solidify modifier if you want to have the normals correct on the inside and outside.

The edge loops can be merged together by selecting both edgeloops, and scaling to zero along the Y axis. All you then need to do is to remove doubles.

• I'll try both methods. Must be nice to have the level of experience you both have. – Randy Van Nostrand Apr 28 '15 at 17:30
• It certainly facilitates projects, that is for sure – VRM Apr 28 '15 at 17:38

When using the mirror modifier you can enable the 'Clipping' option which will clamp (or 'clip') vertices that are along the edge, at the centre of the mirroring:

This will mean that any vertices that are at the mirror edge are clamped together and will not be able to be moved away from where the mirrored halves meet:

Here you can see the vertex is moved towards the middle and is then locked, you won't be able to move it away from the middle again unless you disable clipping.

If you the apply the modifier the vertices along the mirror line will be merged together (as long as the 'Merge' option on the modifier hasn't been disabled).

Seeing as you have already applied the modifier, I would delete half of the model and add another mirror modifier. Move the vertices towards where the halves meet and they will lock to the middle (when 'clipping' is enabled).

Then you can apply the mirror modifier as before.

• For pure speed reasons, I might not recommend that, but good for the answer ratio – VRM Apr 28 '15 at 15:58
• @NoviceInDisguise I included it to act as more 'preventative' measure for any mirroring done in future. – Ray Mairlot Apr 28 '15 at 16:01
• Ah, excellent idea! – VRM Apr 28 '15 at 16:11
• To be accurate: the 'clipping' option prevents you from moving the vertices past the mirror plane. The 'merge' option really merges the vertices. – jasperge Jun 5 '15 at 5:45
• @jasperge You are correct. I was using the word 'merge' to simply mean both vertices will be locked to the same position, but seeing as merge is already a term used with the modifier it didn't make sense. I have slightly reworded it. – Ray Mairlot Jun 5 '15 at 13:04