Compare “Num Selected” in Editor vs. Packaged (via Widget or whatever).
In the packaged version it shows me the “official” number from when you hover over the Static Mesh in the Unreal Editor: 24 Vertices for a Box created in Unreal. It shows 8 in the Editor version. Similar discrepancies for every other Mesh I tried - imported and created in Unreal. Triangle count on the other hand is the same.
I suspect there is a difference in count because of split vertices or something? But I can’t figure out why it would use different methods for counting in the Editor than in Packaged.
The different vertex count is because in the Editor, the mesh that the node copies from is the ‘Source Mesh’, which is based on the imported mesh file and supports multiple UVs and normals per-vertex (depending on the connected face), so that (eg) a cube can be represented as 8 vertices that have different normals and UVs for each of the 3 adjacent box faces.
However a GPU cannot render a mesh in this format, vertices with multiple UVs or normals must be split into unique vertices that have a single unique UV0/UV1/etc and normal/tangent. This is referred to as the ‘Render Mesh’ in the CopyMeshFromStaticMesh input options. In the render mesh for a cube, the 8 vertices will each need to be duplicated 3 times, resulting in 24 vertices.
At runtime, the Source Mesh does not exist, it’s an editor-only concept, and CopyMeshFromStaticMesh can only copy the Render mesh. So that’s why you are getting the 24 vertices in-game.
To try to resolve this, you can do a WeldMeshEdges to try to geometrically merge the split vertices back into a connected dynamic mesh. This will not always work because it’s essentially trying to reverse-engineer your input topology based on overlapping 3D positions, so that will fail if you have (eg) overlapping geometry that is precisely aligned at vertices/corners. But if your render meshes are “clean”, it will generally be ok.
