This section contains tangency constraint descriptions of fixed, free, and floating alignment entities.
An alignment entity's tangency constraint can be changed. For example, you can change a free curve to a floating curve. For more information, see To Work With Changing Alignment Constraints.
Note: If alignment entities are tangential, the overall alignment length does not change when a tangency constraint is changed. If alignment entities are not tangential, the overall alignment length may change when a tangency constraint is changed.
Fixed Entity (Not Constrained)
A fixed entity has the following characteristics:
- It is defined by specifying parameters, such as points or radius.
- Its parameters are fixed in their position. Only you can change the parameters that define this entity.
- It is not dependent on any other entity to define its geometry or to maintain tangency, but its length can be affected by another entity that is attached to it.
- It can be initially created with a tangency association. Fixed entities that start from the beginning of another fixed entity can be initially tangent to the other entity, but the tangency is not maintained when either entity is edited.
Floating Entity (Constrained by Previous, or Constrained by Next)
A floating entity has the following characteristics:
- It is defined by the parameters that you specify and is always tangent to one entity.
- It is always tangent to the entity it is attached to. A floating entity cannot be attached to a free entity, but a free entity can be attached to a floating entity.
- It can be attached only to another floating entity or a fixed entity.
- It is dependent on being tangent to one other entity to define its geometry.
Free Entity (Constrained on Both Sides)
A free entity has the following characteristics:
- It is defined by the parameters that you specify and is always tangent to an entity before and an entity after.
- It must have at least two other entities to add to.
- It is dependent on two other entities to define its geometry.
- It can only be attached between either two fixed entities, two floating entities, or one fixed and one floating entity, but in any order.