Techniques - Head Rotation Using Scale Rotate
I developed this technique after seeing a post on the lost marble forum regarding a recent discovery stumbled on by an anime studio user. It involves bone scaling that results in child bones that rotate in a 3d like manner. As soon as i saw the post i knew this concept could be adapted to a 2d model to replicate a head turning in 3d space. It took some developing but the end result speaks for itself. I termed the technique scale rotate.
Make a face similar to this on a layer.
Create a bone layer. Drag the vector layer up into the bone layer. Create 3 x master bones. One vertical and two on an angle. Use the grid for precision. Name the bone's 1, 2 and 3. Give bone 2 and 3 a bone strength of 3.
With bone three selected create two more bones that run horizontally from the center, name these two bones "left side and right side respectively.
Select the left side bone and open the bone constraints panel. Select scale control bone drop-down and set the scale control bone to 2 and type in a value of 5 into the panel on the right. Select the right side bone and repeat the process selecting 3 as the scale control bone and also give it a value of 5.
Now we need to bind some points to the face bones. Highlight the left side bone, select all points on that side of the face and bind them to that bone. Repeat the process with right side bone binding the right side face points.
We need to create 3 profiles on the time line. Front, left and right. Drag the time line marker off frame 0 to any number, say frame 6. Now highlight bone 2 and select the scale bone tool. Try scaling bone 2. You will see half of the face begin to rotate. Tweak bone 2 and bone 3 untill you get a good left profile. Drag the time line on to frame 12. Create a center profile by copy/pasting the original points from frame 0. Drag the time line on to frame 18 and create a right profile.
Draw the rest of the head and neck using as few points as possible (see image). Select the left side bone and add the two left side chin points to that bones bind point group. Do same for the other side.
Go back to frame 0 and select the bone layer and bone1, (the large center vertical bone). Create 3 smaller bones at the base of the neck starting with the center bone, right then left. bind the three base neck points to the bone at the center base of the neck. Bind the left mid neck point to the left base neck bone and bind the right mid neck point to the right base neck bone.
Select bone 2, (the large left angled bone) and create a small child bone at the left side of the neck and bind that corresponding point to it. select bone 3, (the large right angled bone), create a small child bone at the right side of the neck and bind that corresponding point to it.
Drag the time line along to your first profile and select the translate bone tool. Drag the right parent bone horizontally so the whole face and chin slightly overhang the face to create a perfect profile. Do the same with the other profile. Your head should now perform a perfect rotation from right to left. Drag the parent bone left or right to match your profile.
Time to play. Select the manipulate bone tool and use the left angle bone, bone 2 and drag it around to bend the head up or down. Use the neck bones to adjust the shape of the neck to suit different poses. You can now store your movements as action files for later recall.
Thanks go to Muuvist for the original inspiration and Genete.
Have fun! D.K. — Dktoons
© 2007 David Knight