2011

Associativity allows you to:
■ Reshape the generating profiles to automatically reshape the surface.
■ Work with a group of surfaces as if they were one object. Just as reshaping
one face of a solid box adjusts the entire primitive, reshaping one surface
or edge in a group of associated surfaces adjusts the entire group.
■ Use geometric constraints on the 2D profiles of a surface.
■ Assign mathematical expressions to derive properties of surfaces, such as
height and radius. For example, specify that the height of an extruded
surface be equal to one half the lengh of another object.
As you add more objects and edit them, all these objects become related and
create a chain of dependency. Editing one object can ripple through and affect
all associated objects.
It is important to understand the chain of associativity because moving or
deleting one of the links in the chain can break the relationship between all
the objects.
NOTE To modify the shape of a surface that is generated from a curve or spline,
you must select and modify the generating curve or spline, not the surface itself.
If you modify the surface itself, you will lose associativity.
When associativity is on, the DELOBJ system variable is ignored. If Surface
Associativity and NURBS Creation are both on, surface are created as NURBS
surfaces, not associative surfaces.
Save time by planning your model ahead; you cannot go back and add
associativity after the model has been created. Also, be careful not to
accidentally break associativity by dragging objects away from the group.
Quick Reference
Commands
BREP
Removes the history from 3D solids and composite solids, and associativity
from surfaces.
EXTRUDE
Creates a 3D solid or surface by extending the dimensions of an object.
506 | Chapter 22 Create 3D Models