Speaking of mixing animation, the latest hot topic in 3D software is NLA: non-linear animation. The concept is that you have a library of animation clips that you can mix, match, and loop like video clips in a non-liner editor. In CS3 this is called Motion Flow. The complicated part with NLA is the transitions that the software has to create. Going from a walk to a run might be simple, but what about a flip into a dropkick? As with the mo-cap filters you can let CS3 try its best, and it does a good job, but some situations will require tweaking. Also like the mo-cap filters you can have the software display skeletons of both clips simultaneously. Then all you do is scrub the timeline back and forth and look for similarities, for example, when both clips have the biped moving to put weight on the left foot. So now we have our finished animation mix and of course it can be saved and applied to other bipeds, maybe even other bipeds in the same scene. To make things more realistic you can have Motion Flow apply the clips randomly. More than just having the bipeds start at different times, you can go in and assign percentage chances for a transition to happen. You will see the huge possibilities this opens when used with the crowd system.

Let me introduce the CS3 crowd system by saying that for some people it will be worth the price of the entire package. It is a powerful, fast, behavior based crowd simulator the likes of which I've never used before. Let's say that we've created a 3D visualization of a city park. To populate it we start by creating a motion flow including generic actions like standing around, turning left and right, walking, talking on a cell phone, etc. We can create a variety of different bipeds and assign that flow to them. Now we set up a crowd system where these people will move through the flow randomly and avoid hitting each other or trees. Simply click solve and suddenly believable people populate your park. We'll call those people 'normals' and create a new group called 'tough guys'. We'll give tough guys the same rules normals have and give normals an additional rule that they will give way to tough guys. Let's add a third type called 'wannabees' whose rules are to follow tough guys but avoid everyone else. Click solve and watch the world you created come to life. Not only is it extremely useful, it's actually quite fun. I found myself experimenting with this as if I were a kid putting insects together in a jar and watching them fight.

A group of Bipeds programmed to avoid the sphere.

You can use this crowd system for more than just bipeds. One example included with the software is a flock of eagles circling a large rock pillar. Using a script behavior the eagles flap their wings when going up and glide when descending. The end result looks really good. Another example is a swarm of bees that I'm sure that could be done with particles, but with CS3 you can go even further and have them move to avoid the hand when your character takes a swipe at them. Behaviors can be scripted so you can write your own logic - just imagine the possibilities. Now you probably have the same question I did, 'sounds awesome but how fast is it?' It's actually quite speedy. With a decent machine simple crowds are nearly real time and it goes up from there. I had one fairly complex crowd and when I got back from the fridge with a beer it was done solving.