Does EdgeSplit modify geometry? I'm making robot models exported from SolidWorks look better by smoothing the shading of the faces, here is my work-flow:


Import mesh
Remove double vertices
Smooth faces
Apply EdgeSplit
Export final model


This works great but I am not sure of one thing, from what I understand the EdgeSplit modifier only modifies the vertices normals on specific regions of the mesh (given the split angle).

When applying the work-flow above on some meshes (example), the poly count changes and I don't understand why:


Original file: 230 vertices
Removed doubles: 226 vertices
Smooth faces: 226 vertices
After EdgeSplit: 421 vertices


Why is the EdgeSplit affecting the poly-count in some cases and other not?
Yes, the Edge Split modifier does modify the geometry.

Edge Split works by actually splitting edges, i.e. making an edge two separate (overlapping) edges.  This is why your vertex count goes up after applying edge split, each vertex which is on an edge that got split is turned into two vertices.



Note how the vertex became three separate vertices after Edge Split.