How to remove split mesh seams
Whats This Tutorial about
This tutorial will show you how to get rid of those annoying seams you get when splitting a part of a mesh. This tutorial will explain why it happens, and how you can fix it.
To illustrate the problem, here's a picture showing a unit for the M2TW mod Rising Summer.
On this picture you can clearly see a vertical seam all the way across the middle of the unit.
Unit by Odoaker
Whats Causing This
The seam is caused by the way the light hits the surface of the mesh, and the way the normals work.
On a mesh with a single smoothing group the normals look like this:
(grey is the mesh, green the normals)
As you see The normals gradually transit into each other, making a smooth transition.
When you split the mesh on that edge, you also split the left side from the right side at that point, meaning that the normals can no longer transit into each other, resulting in a sharp edge. where if the hit hits the left side it will show a different intensity then the right side, and because there are no longer any normals in between to provide a smooth transition, you get a sharp edge.
As seen, the normals can now only come straight from the plane's surface. resulting in a sharp edge.
How can you fix this
simple, but it requires a bit of work. The best option is to not split the mesh, but unfortunately you need to do that for M2TW and RTW models, so that's not an option.
So how can we fix it? Well, you just need to make sure that the normals on both sides of the seam are in the same direction.
(seam in red)
That way the light seam disappears, and you get a smooth transition instead of the sharp seam line.
A simple cut along a straight plane will do:
(seam in green)
Thats how you get rid of those annoying seams.
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