thinkingParticles offers many powerful features that are generally new to 3ds Max users. One new feature is the use of Hierarchies to arrange animation events and objects in your 3D scenes. The Particle Group Tree View is the place within thinkingParticles where you set up these new hierarchies and enables you to freely arrange how particles are grouped together.

The Particle Group Tree View

Nearly all of the advanced effects that you can create within the system are based on the fact that thinkingParticles is able to store particles in separate Groups. Those Groups are like containers that encapsulate the particles placed within them. These containers can also contain other smaller containers and so on. By creating and using these groups, and placing them into a single hierarchy you can create particle animations where only certain particles (those within a specific Group) get affected by a set of conditions or rules while other groups of particles aren't affected at all. What's more is that particles that reside in one Group are not permanently locked or associated with that group. Particles can be passed from one Group to another within the system at any time, based on any set of rules or conditions you set up.

Now by default, thinkingParticles uses the ALL Group as the base container to store particles when no other groups are available. The ALL Group is a permanent, base Group and can't be deleted or moved by the user. It also acts as the Root of any hierarchy and branches you create. This gives you the ability to access all of the particles in your particle system regardless of the hierarchy - simply select the All Group and make your changes here.

A practical example for using groups and hierarchies can be explained as follows:

Imagine you were given the complex 3D scene to animate described in the Introduction where you need to animate a spaceship taking off, flying through a meteor shower, and then getting hit by some meteors. When the meteors collide with the ship, they are supposed to create debris and cause damage to the spaceship’s hull.

More than likely, you would have to create several particle systems to handle the various tasks such as the rocket smoke for takeoff, the meteors, the collision meteors, debris, etc. Then you would have the task of trying to coordinate everything so that the particle animations are synced up with the rocket and meteor motion and believable.

thinkingParticles however, allows you to build a single particle system that handles all aspects of the particle animation required. This is an important concept: thinkingParticles only needs ONE particle system to create multiple particle animations. This is due to the nature of the Particle Groups and hierarchies. You can build one Group of particles that will represent the meteors, another to represent the rocket exhaust, another to represent the debris, and so on. Each group in the hierarchy can also have sub-groups, so for instance, the debris group could have a sub-group called dust that would represent the small particulate matter that flies off of the debris chunks as they spiral away after the collision. There is no limit to how you can create your hierarchies.

Now while you may think that this one system approach may make the setup more complicated, in fact, it offers you not only a single centralized control point to tweak all of your particles, but also removes the need to “time” everything so it is in sync. Since thinkingParticles is rule-based, if the client wanted to later change the timing of one of your particle animations (perhaps the rocket was to fly through slower or faster), it would not be necessary to re-work the new sections; the rules would automatically account for the changes and react accordingly.

There are several things you need to consider when you want to make heavy use of particle groups. First thing you should do before you start creating groups is to do some planning and think about the how you'd like to set up your Groups and hierarchies. Try to determine the different kinds of particles you want in your scene (based on behavior, interaction, etc.) and break them down accordingly. The more planning that you do prior to diving into your animation, the fewer surprises you will have once you get into it. Of course, thinkingParticles does allow for the creation and manipulation of Particle Groups at any time, so if you don't anticipate everything at the beginning, you won't have to start from scratch.

To create new Particle Groups, simply click on the Create button beneath the Tree View. Once you've got a new Group created it will be named Group by default. As this name is not terribly descriptive and is given to all groups you create, when you generate a new group you are strongly encouraged to rename it immediately to something more recognizable.

To rename a created Particle Group you should take your mouse and perform a slow left-click over the name. This process is identical to renaming a file using standard Windows controls. You'll click once to select the group (it will highlight), then do the slow left-click to open up the naming dialog.

Once you have several groups, you might decide that you want to re-order them or make one group a sub-group of another group. To do simple re-ordering of the various groups, you can use the UP and DOWN buttons beneath the Tree View. You also have the ability to drag-and-drop one Group onto another in order to make it a sub-group of that group. This process is sometimes called nesting, and it is discussed in more detail below. You can even drag and drop groups onto the All Group to effectively bring them back up to the main branch level.

As it is really essential for you to understand how the Groups and Hierarchies work together and inter-relate, let's look at a more complicated setup. Check out the sample particle Groups in the illustration below.

In the illustration above you can see that there are 3 main particle Groups (All, New Particles and BurnOutSmoke) along with 5 nested particle groups (SpaceshipFragments, CarFragments, Bullets, Gunsmoke and LeftWheel) and each particle group can be individually accessed by its name simply by clicking on it. Whenever you create a Sub-Group of particles, any rules that affect the upper group in the hierarchy will affect the particles in the sub-group. So if you apply a set of rules to the Bullets group, the same rules will apply to Gunsmoke sub-group as well.

One more important bit of information regarding Groups. When you create them in the Particle Group Tree View window, they are also automatically created in the Groups Create Rollout (shown below). This is done so that you can use these groups within the Wire Setup View. Moreover, the Group nodes created will share the same naming conventions as within the Particle View Tree View. In the image below you can see that all of the groups from the example above also exist within the Create Rollouts with the same names.

Left Click onto the Tree-view Icon to bring up a color gradient dialog. Choose any particle group color to visualize the particle group in the Viewport.

New Particle Group Right Click Menu Option: Right-Clicking on any particle group name brings up an new context sensitive menu.
For each particle group name clicked; a list of operators using or referencing this particle group is listed. Clicking any of the Operator names will automatically bring up and select the DynamicSet in question.
This feature is great for debugging complex DynamicSet setups containing hundreds of nodes.