I have made a face in 3D with his lips closed, but I want to create the interior of his mouth for animation even if we do not see it currently. How can I do that, without open his mouth and therefore deform my mesh ?
Thanks for your help.
Hi @123EE_M!
There are a few functions that are going to be useful here.
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Basic Mesh Visibility operations. You can hide the surrounding mesh area to make only the mouth interior visible. This will be even easier if you have assigned distinct poly grouping. Then you only need to shift+ctrl click on them to hide or reveal them.
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The visibility functions in Tool> Visibility. These will give you finer control over the visible polygon selection. For instance, if you could use the functions in the above section to hide all polygons but the very rear of the mouth cavity, you can “grow” that selection until it contains all, or most of the polygons of the mouth. Then these polygons can be polygrouped to make hiding or masking them much easier.
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The Brush> Auto Masking> Topological option. This can make it easier to sculpt on, for instance, the upper lip without affecting the bottom lip.
Hope that’s helpful! 
[Edit] If you were asking about how to create the mouth cavity, just say so and we can go over that as well. Thanks!
Thanks for your advice I did it by polygrouping the lower jaw and lip to the rest, now i did a hole and create the mouth-bag but I have another question, how can I sculpt the mouthbag ? Indeed, I can’t sculpt it because it is hidden behind the skin and so I can’t not clearly see my modification when I draw and even less draw on it without affecting the skin ? Should I polygroup the mouthbag ? And Is it better to have teeth and tongue in another subtool ?
This is where the functions I described above come in. You would hide the face and any other geometry in the way to sculpt on the mouth cavity. This is much easier to do if those portions of mesh are separate polygroups. Then you need only Shift+Ctrl click on them to hide them.
I would. But as long as the face is it’s own polygroup, it will be easy to hide with a click.
Generally, yes.
Sorry , I am a bit noob with polygroup, I understand it is useful to isolate part of mesh but how can I deal with the gap created between the polygroups ? I can’t sculpt anymore between the polygroups without increase this gap
Thanks again
Have you polygrouped the mesh portions, or have you actually split them into a separate subtool?
Mesh portions that you need to be able to sculpt on simultaneously in unbroken fashion should be part of the same subtool, and separated by polygroups. Polygroups should not separate as I’m seeing in the picture. Although, if you sculpt across the border of a polygroup while one of them is hidden or masked, it can result in a seam or a crease in that location.
Subtools are completely separate meshes, and cannot be sculpted on at the same time as geometry in another subtool.
So in this case, you’d ideally want your face to be one polygroup, and the mouth cavity to be another polygroup that ends at the inner lips. In this way you can quickly hide the exterior face to work on the mouth cavity. If you happen to sculpt across the border while the other polygroup is hidden, it will be in an out of sight location where you can touch up any seams.
They are in the same subtool in the picture, just other part are hidden with ctrl shift, currently i have just 4 subtool: Face, eyes, teeth and body. Here I have five polygroup : ears, eyes area, mouth cavity, the lower jaw with the lower lips, and the rest of the face