# Trimming and Extending Curves

To trim or extend curves

- On the Command Panel, click on
**Geometry** and then **Curve**.
- Click on the
**Modify** action button.
- Select
**Trim** from the drop-down menu.
- Enter in the appropriate values for
**Volume ID(s)**. This can
also be done using the **Pick Widget** function.
- Select
**Curve** or **Vertex** from the Trim At menu.
- Enter in the appropriate settings for this menu.
- Click
**Apply**.

**Trim Curve <id>
AtIntersection {Curve|Vertex <id>} Keepside Vertex <id> [near]**

Curves can be trimmed or extended where they intersect with another
curve or at a vertex location. When trimming to another curve, the curves
must physically intersect unless they both are straight lines in which
case the **near** option is available. With the **near**
option the closest intersection point is used to the other line - so it
is possible to trim to a curve that lies in a different plane. When trimming
to a vertex, if the vertex does not lie on the curve, it is projected
to the closest location on the curve or an extension of the curve if possible.

The **Keepside** vertex is needed to determine which side
of the curve to keep and which side to throw away. This vertex need not
be one of the curve's vertices, nor does it need to lie on the curve.
However, if it is not on the curve it will be projected to the curve and
that location will determine which side of the curve to keep.

If the curve is part of a body or surface, it is simply copied first
before trimming/extending. If it is a free curve a new curve is created
and the old curve is removed. The figures below show several examples
of trimming/extending curves.

## Trimming a Curve

Figure 1. Trimming a Curve
to an Intersecting Curve

Figure 2. Trimming a Curve
to a Non-Intersecting Curve Using the Near Option

Figure 3. Trimming a Curve
to a Vertex

## Extending a Curve

Figure 4. Extending a Curve
to An Intersecting Curve

Figure 5. Extending
a Curve to a Non-Intersecting Vertex Using the Near Option