High > low poly workflow (blend shapes) question

otto2302

Hi,

New to this forum so feel free to move / delete post if this is not in the right area.

I have sculpted a rough anatomical body and a head. I have sculpted secondary details to the head and I'm ready to stop dynameshing and move to subdivision levels. 

My question is about mouth cavity for a model that is going to be rigged and animated. We are going to utilize blend shapes (shape keys) for deformations of the face. This is my first shot for making a facial sculpt to be rigged and animated later, and I'm wondering whether the high poly sculpt (that is used to project details to the retopoed mesh) has any need for the mouth cavity to exist in itself?

Obviously the blend shapes will be applied to the [clean low poly] model that is going to be rigged and animated later. When I retopo the mesh from the high poly sculpt, I can project details to it and then extrude the mouth cavity inwards? Is this the typical workflow? I haven't seen many high poly sculpts with mouth open when browsing images of high poly sculpts. I'm wondering whether the mouth cavity modelling is reserved solely for the low poly model. 


Here are few explorations of the high poly model with a mouth cavity blend shape. I'm assuming that this stage is supposed to be saved later for the low poly model.


(Above) Base sculpt 


Mouth opened, cavity pushed in and blend shape 1 assigned


Mouth cavity closed on the same 3D layer, the corners of the mouth obviously less natural with only little rework done.

pior

Outside of some very specific cases your sculpt will likely have zero relevance to the creation of the actual blendshapes.

In other words, let go of your focus on the "pretty highpoly sculpt" and put all your attention on the lowpoly model, which is the *actual* asset at the end of the day. 99% of the time this is the asset on which the blendshapes will be created, and by that time the sculpt will be a thing of the past (that you'll likely wish you'd spent less time on in retrospect ). It hardly matters if it has a mouth cavity or not, because the low obviously will have one. One good practice is to simply model the sculpt with a slightly open mouth - just enough to create a cavity if so needed, but not fully open either. It'll give the sculpt a bit of a dumb look but as said, it has zero relevance to the end product anyways.

Some even sculpt the eyelids half-closed, to anticipate and avoid any stretching on the final texture. But then again ... another way would consist of not even bothering about sculpting that sort of stuff and just building it directly in low - even throwing in a temporary rig or set of blendshapes to open/close the eyelids at will. Doing things that way allows one to tackle technicalities like mouth and eye behavior on day one, without involving days or weeks of zeedbrushing.

Overall you need to stop thinking in terms of "highpoly first, lowpoly then", especially on things like animated faces. It may sound counter-intuitive but that's just not how things work for this kind of assets. The two really need to be worked on in parallel, non-linearly, otherwise you'd end up wasting a ton of time and energy.

if anything I'd rather recommend working on one animated face asset without *any* sculpting/highpoly first - just straight to low, like in animated movies, and dealing with all the technicalities there (eye setup, expression blends, and so on). Once you have that done you'll have 80% of the work done for the next one since all the tech can be reused. And that way the sculpting will be an absolute breeze, likely doable in a day or so.

otto2302

pior said:

Outside of some very specific cases your sculpt will likely have zero relevance to the creation of the actual blendshapes.

In other words, let go of your focus on the "pretty highpoly sculpt" and put all your attention on the lowpoly model, which is the *actual* asset at the end of the day. 99% of the time this is the asset on which the blendshapes will be created, and by that time the sculpt will be a thing of the past (that you'll likely wish you'd spent less time on in retrospect ). It hardly matters if it has a mouth cavity or not, because the low obviously will have one. One good practice is to simply model the sculpt with a slightly open mouth - just enough to create a cavity if so needed, but not fully open either. It'll give the sculpt a bit of a dumb look but as said, it has zero relevance to the end product anyways.

Some even sculpt the eyelids half-closed, to anticipate and avoid any stretching on the final texture. But then again ... another way would consist of not even bothering about sculpting that sort of stuff and just building it directly in low - even throwing in a temporary rig or set of blendshapes to open/close the eyelids at will. Doing things that way allows one to tackle technicalities like mouth and eye behavior on day one, without involving days or weeks of zeedbrushing.

Overall you need to stop thinking in terms of "highpoly first, lowpoly then", especially on things like animated faces. It may sound counter-intuitive but that's just not how things work for this kind of assets. The two really need to be worked on in parallel, non-linearly, otherwise you'd end up wasting a ton of time and energy.

if anything I'd rather recommend working on one animated face asset without *any* sculpting/highpoly first - just straight to low, like in animated movies, and dealing with all the technicalities there (eye setup, expression blends, and so on). Once you have that done you'll have 80% of the work done for the next one since all the tech can be reused. And that way the sculpting will be an absolute breeze, likely doable in a day or so.

This is something I was 97% sure of, just needed the confirmation. Thanks.

I'll probably do retopology of the entire character very soon (before moving to the sculpting details like skin pores, grooves etc). in 3DCoat to get a clean topology base mesh to get started with rigging etc. I can always do the detail sculpting later in zbrush to project the displacement maps.

As you said, I'm not really worrying about zbrush sculpting right now, the technical aspects of a humanoid character are the hot potato for me.

Eric Chadwick

pior ++