Unity is removing vertices from my mesh when I want to keep them

I’ve tried various settings for importing with no luck. I am working with OBJ format mainly but the same thing is happening with DAE too.

In brief I want to be able to do morph target animations. So say I have two models of a human head - one model is a neutral position and the other is with mouth open. My algorithm would compare the two models vertex by vertex and move vertices around depending on the strength or weight of the morph.

For this to be possible, each model has to have the same number of vertices.

But when I import my two models I see they have either lost or gained a few vertices. I tried things like turning off ‘Optimise Mesh’ as that sounded like it might do something I find undesirable. Is there some other setting I can change ?

I’d like Unity to do nothing to my meshes apart from import them and respect the vertices. Is this achievable please ?

Many thanks for any advice. I have just started with Unity by the way.

Unity supports morph-targets - it’s called BlendShapes, so you don’t have to code it yourself.