A technique called Inverse Kinematics can be used to animate skeletal motion. The problem with the traditional way of making skeletal motion is one of starting at the wrong end. For example, if you wanted the character to brush her hair, and her hand was by her side, you would start at the shoulder, rotate the upper arm to an approximate position, then move the forearm from the elbow joint, only to find she could not quite reach her head without adjusting the upper arm again. The problem is reduced with inverse kinematics. Instead of working from the shoulder out, you click on the tip of the finger and drag it to where you want it, causing all the preceding joints to be positioned automatically.
The final stage of creation is Direction. This is like being on a movie set. You have a camera, lights and actors. You assemble your cast of characters and tell them what to do. The cast members and their actions may be ones you have created or picked from the existing library supplied with the program. Upon opening Direction you are presented onscreen with a top view of the studio floor represented by a grid. To place the camera click the add button, click the spot where you want to place it then click the camera button. Characters and lights are added in similar fashion. You add a target to tell the camera where to point and a click of a button lets you look through the camera viewfinder. Everything is represented in wire-frame at this stage for speed of drawing. When everything is set you can test the action by having a run through in wire-frame form. This is saved to disk for repeated playing, rather like watching a line test.
When everything in the scene is the way you want them to be, move on to Render. This is where the surfaces are put on the wire-frame models, with lighting, shading, and shadows. A:M will render at any resolution you choose up to film resolution. Obviously the higher the resolution the longer the pictures will take to render. The speed of rendering depends on the complexity of the picture and the power of the processor. It compares favourably with other PC rendering programs. A:M is a true rendering program producing photo-realism if required. The rendering speed I get with A:M compares favourably with other PC rendering programs I have tried. It will render single frames as 24-bit TGA files or movies in the native format of the machine in use; FLI or FLC on the PC, Quicktime on the Mac and Silicon Graphics movie format on the SGI.
There are many other features too numerous to deal with in this review such as channels for modifying the actions, motion blur, alpha buffers and network rendering. The program has a great deal of power but every part has default settings so you do not need to be an expert to get started.
Printed in Animator Issue 32 (Spring 1995)