# Shape Keys - opening the mouth

Any advice on the best way of opening the mouth using Proportional Editing or rotating the bottom jaw from the pivot point/3D cursor? It's the latter I'm trying to achieve. Sadly, the jaw always looks a bit too wooden, like a ventriloquist dummy's.

Thanks

• Please show your work with Blender screen captures. Yes there is an attached Blend file. Still it clarifies your question to readers to include screen captures in this question and all future questions. Probably the reader above could make the observation and corrections you need without opening your file, if you choose a meaninful screen capture. – atomicbezierslinger Dec 6 at 16:18
• I'm sorry if I sounded rude. If you included the armature and the original weights in your file, it would be easier to demonstrate some weights which can open the mouth with only the jaw bone. – Leander Dec 6 at 16:49
• Updated the original post with an image. I'm aware I could use armature instead, and I do have some set up, but I'm practising with Shape Keys at the moment. Plus, I had to delete some stuff for that save file as it was over 30Mb – DustyShinigami Dec 6 at 16:49
• Bones/Joints are much better suited for movement which rotates around a pivot point, namely the eyelids and the jaw. Both will interpolate strangely if their not pivoting the base of the movement (where the bone would sit in reality). Shapekeys will only switch between states and are best suited for the eyebrows, mouthcorners and and other movements which rely more on muscle contractions instead of mechanical relations (like bones). – Leander Dec 6 at 16:54
• Can't seem to get Weight Paints to work with my jaw bone anyway, which is weird because I swear I did at one point. I keep trying to parent the head to the jaw bone and applying Automatic Weight Paints, but nothing happens. If I paint the jaw in red manually, manipulating the bone doesn't do anything – DustyShinigami Dec 6 at 17:09

## 1 Answer

From my comment

Bones/Joints are much better suited for movement which rotates around a pivot point, namely the eyelids and the jaw.
The Jaw will interpolate strangely between open and closed if it is just shifting between a shapekey. A bone would ensure a rotation similiar to the real world jaw bone.
Shapekeys are best suited for the eyebrows, mouthcorners and and other movements which rely more on muscle contractions instead of mechanical relations.

Edit: To understand the images illustrating this post, you must note, that I have used a custom weight paint range. Every vertex weight above 0.000001 looks similiar to the standard weight settings. However, a weight of 0.0 is set to white. I did this to be able to tell the difference between a very small weight (e.g. 0.00001) and actually no weights, which is not possible with the standard mapping of blue.

## Weight Painting the Jaw

1. Make sure all of your head geometry is associated with the head bone.
2. Add the jaw bone, make sure that
• there is a vertex group named exactly like the jaw bone
• the jaw bone has deform enabled
• the jaw bone is part of the armature used by the the mesh (via the armature modifier)
• your geometry is not unnecessarily dense (it seemed you have applied the subsurf modifier, this makes the process very difficult. I would unsubsurf the model 1 step with the decimate modifier.)
• in weight paint mode, Auto-Normalize is checked
3. Lock all groups except for the head and jaw vertex group.
4. Roughly paint the jaw to the jaw bone.
5. Now open the jaw with the bone and make sure the complete jaw is fully assigned to the jaw bone.
6. Now choose the the mix brush and paint weights of approximately 0.5 on the corners of the mouth. Choose other quantized weight for other areas if needed. Roughly block out the correct shape. You can raise the mouth corners by adding weights to the head vertex group and you can lower them, by adding weights to the jaw group.
7. Using the blur brush smooth the area. Then use the add brush with a very fine Strength to shift single vertices untill the desired shape is reached.

Image shows the head's weight group.
• Thanlks for this. I'll give it another go. Looks like the reason why I couldn't get it working before was because I'd forgotten to set the bones to Deform. Also, what exactly does Auto Normalise do? Thanks – DustyShinigami Dec 6 at 18:59
• The manual explains it well: "Auto Normalize_ Ensures that all deforming vertex groups add up to one while painting. When this option is turned off, then all weights of a vertex can have any value between 0.0 and 1.0." In this case, we want weights to be removed from the head when we add them to the jaw. – Leander Dec 6 at 19:04
• Not having much luck with this; I find weight painting to be tedious, finicky and time consuming. :-\ – DustyShinigami Dec 6 at 20:44
• May go back to using Shape Keys; I was finding those easier to use. I suspect the book I’m following suggests to use them for the mouth as well – DustyShinigami Dec 6 at 21:03
• I can't, for the life of me, get this nailed. :( No matter what brush I use, I can't seem to match how you've done it. I keep trying to paint over the vertices and nothing happens. I can't seem to get passed this ventriloquist dummy look. I've updated the first post with an updated image showing what I currently have. – DustyShinigami Dec 7 at 1:02