Graphics Reference
In-Depth Information
that allows you to select different elements of the scene easily, and at differing levels
of detail.
If your hierarchy is not logical, your fi le may be confusing to others. Worse, it
may not animate or render properly. Grouping affects animation because animation
is applied to individual nodes. If those nodes are part of a group, then all nodes
subordinate to the animated node will be affected by the animation as well. If you
have the tires on the right side a car grouped together, for instance, they will rotate
together, even if their opposites on both axles remain motionless.
If you move a subordinate node from its position below an animated node, it will
immediately cease to be animated by that node. In the same way, if an animated
node is added to a group, all of its new subordinates will inherit its animation. For
this reason, objects that will be animated independently of other scene elements are
kept independent at the group level as well.
9.6.4
Layers
Most 3D applications have layers , a method of sorting selected items under arbi-
trarily named separation barriers. Often layers have several attribute fl ags that may
be set for all objects within them. The most common are visibility and sensitivity . 1
If the sensitivity fl ag is off, objects on that layer cannot be selected, but they will be
drawn to the screen as long as the visibility fl ag is set to on.
Layers are useful for creating temporary working space as you construct an object
or a scene. With them, you can store stray objects that are either unfi nished, in the
way, or temporary save objects just before you execute a risky modeling operation.
9.6.5
Materials
Material assignments are another way to organize data in a 3D fi le. With these, you
may create several different materials for your scene, like wood, stone, and glass, and
then assign individual polygons, groups of polygons, or polysets to them. Once this is
done, most applications will allow you to select objects based on material assignment.
9.6.6
Node Chart
When you group objects in your scene, it will create a node chart to show how the
objects, represented by nodes, are related. It won't always sort objects the way you
want it to, so you may have to edit it so that the nodes appear in a logical order. For
1 Like other terms of this type, the actual name of the function will vary depending on which appli-
cation you are using.
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