Blend shape vertex numbers

Unity Engine
1

From a performance standpoint does the total number of vertices in a model, which uses blend shapes, matter when the blend is performed? Or is the overhead contained in just the delta of the vertices that move?

For example, say I have a model which has 20000 verts and 200 of them move during a blend. Would that be more expensive (to blend) than a model that has 400 vertices with 200 moving during the blend.

The reason I ask is I have a character for which, from a production pipeline pov, it would be useful if it was all one mesh. But it has a very small number of blending vertices which are currently a separate object.

If I were to attach the blending object to the main mesh, would I see a performance hit?

Thanks in advance

2

I don’t think it really has a misurable impact. Nowadays you’re able to push an insane number of vertices, not only on high end PC hardware but on mobile too.
Your real bottlenecks are the number of draw calls and the number of pixel processed (so shaders, post processing and so on).
Sure if you literally have hundreds or thousands of characters on screen it -might- have an impact, but again you’ll have other problems to solve first (draw call, how to process so many characters efficiently and so on).