There are three types of attributes, as described in : inherent, predefined, and custom. Some nodes and compounds automatically get and set certain attributes of any of these types, but you can also get and set particle attributes on their own.
Attributes are used inside many compounds. In the compound property editors, they are disguised as parameters that you can set. For example, when you set the Initial Values parameters in the Emit compounds, you are setting the Init_AttributeName attributes (see ), as well as others.
Attributes are used in the Get Particle AttributeName and Set Particle AttributeName compounds. These compounds make it easy for you to quickly use specific particle attributes. They are simply the Get Data and Set Data nodes with a specific attribute already selected for you.
Getting attribute data from particles and setting attribute data for particles is something that you'll probably need to do a lot when creating ICE particle effects. In fact, you've already set attribute data if you have set parameters in most particle compounds.
You can get and set attributes for the particles in a point cloud. Some of these particle attributes are exposed in special Get Particle and Set Particle compounds to give you a head start, but you can also get a simple Get Data or Set Data node and expose any attribute in it that you need.
These compounds use the Self. string as a reference plus the appropriate attribute name. For example, if you want to use the Age attribute, choose the Get Particle Age compound; or if you want to set the Size attribute, choose the Set Particle Size compound. Everything's already set up for you.
Drag a Get Data or Set Data node into the tree from the Data Access group on the Tool tab of the preset manager. Then enter the name of the referenced object or the Self. string in the Reference text box — see for information on this.
If you used a Get Particle AttributeName compound from the Getters group, or a Set Particle AttributeName compound from the Setters group, the attribute is already specified for you, but you can change it using either of the following ways.
The ICE attribute shaders allow you to access a particle's ICE attributes that are driven by ICE trees. You can also apply the Attribute shaders to geometry that is used as shape instances on ICE particles.
These shaders allow you to control your shading based on calculations done by an ICE tree, thus creating a link between data in the ICE tree and data in the render tree. For example, you can make smoke dissipate or a color change with a gradient depending on the velocity of the particle.