Wondering how it works.

Let's say Saints Row 3,4

Skyrim 5

Falout 4

These games can customize player face and body,how it works and is there any tutorial guide you to do a simple body modelling system by yourself?

I mean how to write code to achieve modelling in game,not modding for these games.

For example we want to the user to be able to lerp between male and female by a slider, you can do this by modeling both from the same topology.

Assume we already have a male base model. Move all vertices so it looks female, but don't add or remove vertices.

For each vertex store the difference to the original male position. (we call this a relative 'morph shape',  or 'blend shape').

In the game the character then is made by male_vertex + female_offset * gender_slider.

You can also handle details this way, e.g. make just the nose large (so most vertex differences are zero). You can combine all options simply by: male_vertex + female_offset * gender_slider + nose_offset * nose slider...

The second option to consider is to affect skeleton bones, e.g. Male: wide shoulders, narrow pelvis, Female: narrow shoulders, wide pelvis.

You can utilize scale and sheer as well for skinny / fat and so forth.

But with caution, as altering skeletons also affects its animations.

Thank you very much.

Finally understand how it works,and I will try to make such system myself for fun.