Is extruded face like this okay in game retopo especially for rigging (image included)

hegvbwkeuyrv

pretty straightforward. I think the result is pretty nice except for some artifacts that i need to solve later. Will i have problem rigging this later? especially for the skinning part cuz the vertices are INSIDE the armor.

zachagreg

If the chest of the actual character goes completely behind the armor with out some reasoning behind why it would to that is a bad idea. For one it wastes precious UV space where it could be better used providing resolution to other parts of the mesh. A second reason this would be bad is because it complicates the process of weighting and animating the model like you're asking about.

Technically the answer to your question is no as it can be done, however, there is not much of a reason to make things more complicated for yourself if you are never going to see the model without the chest armor. The chest armor should just be placed directly onto the skin of the mesh in your highpoly and then on your low poly not even including the concave area between the chest and the armor.

By doing this you save, polys, texture space, and various headaches that come with weight painting such areas.