Like all the other aspects of this 3D modelling project, there are multiple ways to approach the creation of a mouth. You could try and alter your mesh as it is but I think this is a good point to introduce the “Boolean” modifier.
The “Boolean” Modifier
This modifier basically takes two objects that have been intersected and applies one of three boolean modifications:
- Difference: Combine two meshes in a subtractive way
- Union: Combine two meshes in an additive way
- Intersect: Keep the part of the mesh that intersects with the other selected object
The reason why this will work for us, is that we can create a shape that mimics the gap of the mouth and then delete the difference from our Sackboy mesh.
For this we will need a modified cube, so go back to Object Mode, add a cube and then flatten it into a wedge that will eventually sit through Sackboy’s mouth:
You’ll notice I’ve really flattened one end of the cube, this just means the edge of his mouth should look a little better when we’re done. Next you need to add a bunch of edge loops from the top view in order to give this cube some vertices that our curve modifier can work with:
Next up we need to add some curves to give Sackboy a smile, we’ll start with his side on curvature. To create a curve we have to first “Add” > “Curve” > “Bezier” in Object Mode. Then Rotate it so it’s facing directly down the Z axis, you can then tweak the curve to match Sackboy’s smile from the side, something like this:
Then all we do is select our mouth wedge and add the “Curve” modifier. Select your BezierCurve as the “Object” and then move your mouth onto the curve:
So we can now apply that modifier, delete the bezier curve and do it all again for the curvature at the front:
And now we have a perfect, mouth-shaped wedge! Place it into position and now we just select the Sackboy mesh and add a Boolean Modifier with these settings:
And voila! We’ve subtracted a perfect mouth-shaped wedge from our mesh. Make sure you apply your modifier and then delete the “mouth-wedge-cube-thing” and the mouth is done!
We now have the general gist of Sackboy so it’s probably a good time to take a picture of him to see him in all his glory!