Fiziwig's Animator Studio Tutorials

Gary's Anime Studio Experiments is my collection of experiments, in tutorial form, put together while learning how to use Anime Studio. I hope you find them useful.

On Dec. 22, 2007, a Lost Marble Anime Studio Forum member, DK from Australia, posted an innovative method of accomplishing head and body turns in Anime Studio. Read the original post here. This ingenious method of rigging a character to simulate 3D turns is relatively simple, and gives excellent results. Here is a sample of the results as drawn by DK himself:

There are, as they say, a lot of ways to skin a cat. And there are a lots of ways to rig a character for animation. This is only one approach. I will be covering many different approaches later on, so if this particulat method is not to you liking, be patient, there are many other ways to approach this task.

If you simply look at the bone rigging for this character it might be a bit overwhelming. It looks like an extremely advanced topic. But rather than simply present the completed bone rigging for the head and body turn, I'm going to start with some basic principles of bone motion and scaling, as well as the clever "self-masking" idea also developed by DK to handle parts of the drawing which need to disappear at certain times during the turn. Taken one small step at a time, we can come to understand each part of the process so that we can adapt it to our own characters.

In particular, I'm not at all happy with the outcome of my earlier head and body turn experiments with the Egg Man. Particularly since I am trying to put together a short 3 minute story animation staring the Egg Man.

Scaling a bone changes its size. When we think of scaling, therefore, we might think only of changing the size of whatever object that bone controls. However, something else happens when we scale a bone. While the tail of the bone remains fixed in place, the tip of the bone moves closer to, or farther from the tail. If we place a child bone at the tip of the first bone, that child bone will move in response to scaling of that first bone.

At the top of the figure is the original bone before scaling. Below that, we have stretched the bone, and in the process, moved the child bone, thus moving any object or layer that is bound to this bone. So that I can more easily discuss them, I'm going to call the horizontal scaling bone the Scale Control Bone, and the vertical bone that controls the points or layers, the Point Control Bone.

In order to do head and body turns using a single scale control bone we will need to have that bone controlling several point control bones that do the actual moving of the body parts. We also need to take into account the fact that when scaling in one direction, we may want some of the objects or layers to move in opposite directions from each other. We also want to be able to turn the whole figure, so we will need a single root bone that controls the placement and 2D rotation of the whole figure.

Here's an example of how two objects can be controlled with one scale control bone. Starting with a new empty project, we create a bone layer, with two vector layers. In one vector layer we draw a red circle, and in the other, a blue circle. We'll name the layers accordingly.

Next we will place a single vertical root bone to control overall position and rotation of all the objects in this collection. From the tail of the root bone we will draw the scale control bone horizontally as show below.

At this point we could put a single point control bone at the tip of the scale control bone and bind it to the two layers, however, that would really not accomplish anything we couldn't have done by simply moving the layers with the translate layer tool.

What we need is for this single scale control bone to control the two layers differently. In other words, we don't want the two layers moving together, we want them each moving in their own independent way. To solve this problem we introduce the idea that the scale control bone can be used to control the scale of a different scaling bone for each layer. To begin with, each of those bones needs to move with the tip of the scale control bone, and each bone needs to react to scaling in it's own unique way.

To lock these new horizontal bones to the tip of the scale control bone, we use two intermediate bones I call Transfer Bones to transfer the tip motion of the scale control bone to the secondary scaling bones. At the tip of each secondary scaling bone, which I call Offset Bones, is the child bone, the so-called Point Control Bone, which actually controls the motion of the object or layer. To do that, simply bind each point control bone its associated layer; the Red Point Control to the Red Ball layer, and the Blue Point Control Bone to the Blue Ball layer. Here is what the rig looks like, with the bones named as I have named them in the Anime Studio source file given below:

The final step, the step that makes it all work, is to use Bone Constraints on the two offset bones, so that their scaling is controlled by the scale control bone. Select the Red Offset Bone and open the bone constraints panel. In the section for Scale Control, select the bone named Scale Control Bone and set the control value to -1. In other words, when we scale the control bone UP, this offset bone will scale DOWN. Repeat this step for the Blue Offset Bone, giving it a scale control value of 2.5.

In practice, the scale control values for each given situation will have to be determined by trial and error until you find the combination that gives you the motions you want. These values will give the result below. The entire animation was controled only by rotating the root bone, and scaling the scale control bone. All the secondary motions of the red and blue ball happened under control of the scale control bone.

To watch the bones in motion, download the anme file here and watch it in Anime Studio.

At first glance it might appear that the intermediate Offset bones are not necessary. Why couldn't we just use the bone contraint for Position Control on the point control bones, tying them to the position of the Transfer Bones? That seems like it would have the same effect, but in reality the position of a bone is always measured relative to the tip of that bone's parent. The result is that when the Scale Control Bone is scaled, the transfer bones do move relative to the view window, but they do NOT move relative to the parent bone tip. It is this fact that makes the use of offset bones absolutely necessary. It is only by using the scaling of the scale control bone to change the scaling of the offset bone that we can change the position of the point control bone.

Take another look at the animation at the top of this page, paying particular attention to the shape of the nose. In the front view it is a full circle, but as the head turns to the side, that circle opens up to becomes a half circle as part of its outline goes away. The most straightforward way to do something like this would be to use point animation. Start with a circle that has one line segment hidden, and animate the endpoints of the hidden line segment, closing them toegther to form a full circle.

The problem with that is the nose shape would be distorted as the points were moved, and getting to look right through the whole animation would be difficult. The solution is to mask out a portion of the object as it is moved. Here's a simple example where we want the right side of the circle to open up as the circle is moved to the left.

Inside the circle, and above in shape drawing order, is another shape, a tilted square in this example. This inner shape has the same fill color as the circle, and has outlines turned off. The same kind of bone rigging is used as above, but in this case the point control bone is bound to all the points of both shapes except for the single rightmost point of the square mask shape. Now when the cirlce, along with three points of the mask, are dragged to the left, the fourth point of the mask remains behind, stretching the mask shape. Since this shape is higher in shape order than the circle, the outline of the circle hides behind the mask. The result is a circle that seems to gradually open up as it is moved to the left.

You will notice that the line is cut off at a strange angle. A small refinement of the mask makes it possible to cut the line off with a square edge. Two additional offset bones are added at the tail of the root bone. However, these bones are set perpendicular to the scale control bone. Then they have their scale constraints controlled by the scale control bone with a larger control value, -10 in this case. Now the horizontal scale control bone controls the vertical scaling of the gap offset bones, which move the gap point control bones. The mask is chaned to a triangle with one vertex at the center of the circle, which is bound to the same point control bone as the rest of the circle. The outer points of the triangle are bound to the top and bottom gap point control bones. As a result, the triangular mask opens up with lines connected to the center of the circle, insuring that the ends of the line in the gap are always squared off.

This triangular mask has a more limited range of motion, and cannot open the circle far enough to give us a true half-circle. For practical purposes, the angled cutoff on the lines is not really noticable, and is perfectly adequate.