What is Epics definition of vertices?


I am curious as to what Vertices mean in the engine?
The reason for this is the following.

I noticed strange behavior when using instanced materials. Where skeletal meshes would look like they have another mesh on top of them.
While searching for potential bottlenecks in performance i started looking at meshes.

So i took a cube. a Cube has 8 corners. Also 8 vertices.


Then when i view that cube in UE4 4.7.2 that same cube is said to have 24 vertices. However the triangle count appear to be correct.


I would like some clarification as to why the engine states there are higher vertices that what there is please.
This is creating a lot of confusion when viewing meshes to see of they are not too high in vert counts when optimizing.

Is this a bug, are are there in fact now 3 cubes on top of each other and i simply cannot see them because they are skin tight?

A vertex is a unique set of vertex attributes, including position, normal, vertex color, tangents, UVs. In your example each face of the cube has its own smoothing group, which means each corner is actually made of 3 vertices, one for each unique face normal. Then 4 vertices per cube face * 6 faces = 24 total verts.

Unreal splits faces for smoothing, it doesn’t have the system where it can just smooth them to groups based on parameters.

Excellent. Thank you for clearing that up.