In Crysis they show the full body more or less but they still have first person animations that are forced on the arms that aren’t the same as the third person animations. This way they ensure things look good from both angles.
I myself tried to do this and have it look good but it’s hard. If you do full body view from first person wrong, mouse looking will feel wrong. Games like quake, for example, feel great as you look around but you just see floating arms. Just slapping a camera onto a third person mesh head feels really awkward, so you have to go to extra lengths to make things look good.
I actually gave up on the whole full body experience because I cared more about having a solid fun well controlled first person shooter. I REALLY wanted to do it too, believe me. I may revisit it again though. It’s a great way to have your own shadow be in the world.
One thing I tried is faking it by having first person legs and arms but no body. And I’d make the third person mesh cast shadows but still be not visible to viewer. So when you look down you still see the legs, and it’d play the same animation and you see your legs walking. I think this is what they did in Halo 2. However, it was very hard to find a good camera position such that when you look down you see your waist and can’t see where the legs end. The camera needed to be placed much lower than eye level, and it looked good but my eyes were now around my chest, making it look very weird when I walk up to another fellow character. Mouse looking in Halo 2 on PC never felt right either since I could tell the camera pivot was somewhere behind your eye location.
I ended up having to pull some tricks I read others did and scaled the legs vertically by like 2x to do a perspective trick. When you look down things still look pretty normal even though the legs are stretched such that the waist is actually about where your neck would be. And I was then able to still place the camera near the eye level.
In the end, I scrapped this because it still looked kinda bad and I had to limit the look angles so you can’t look all the way down like you can in most other fps games.
Also I read some polls, and people generally said they don’t even like seeing your legs when you look down all that much. The walking animations usually look weird anyway. It looks OK when it’s in third person, but somehow it always tends to look wrong in first person since the legs don’t move quite right. It just takes a ton of effort to do right or don’t do it at all and go with the classic feel which is known to feel great and solid.
One nice thing I learned from this though is all the cool perspective tricks you can do with first person geometry. In UE4, there aren’t separate depth groups for first person view arms anymore, so you can see your gun and hands clipping into walls in all of the samples nowadays. I simply scale my character’s first person arms down to like .25 scale or so. All that matters is the arms generally fit within the collision capsule. In First person view, they still look right, and they don’t clip into the walls. I haven’t had any horrible issues with this yet. It’s not guaranteed to work 100% though because if my character suddenly takes out a huge long sniper rifle, it’ll probably still penetrate a little since I scaled down for the average case. If I change scale depending on weapon, it’ll noticeably change the arm size so you just have to keep it constant.