The Trim/Extend modifier
is used primarily to clean up overlapping or open splines in a multi-spline
shape so that lines meet at a single point. As with the Fillet/Chamfer
modifier, this modifier operates on the splines at the sub-object
level in the shape. When applied to a selection of multiple splines,
Trim/Extend works as it does on a single spline.
To trim, you need intersecting
splines. Click the portion of the spline you want to remove. The
spline is searched along its length until it hits an intersecting
spline, and deleted up to the intersection. If the section intersects
at both ends, the entire section is deleted up to the two intersections.
If the section is open on one end and intersects at the other, the
entire section is deleted up to the intersection and the open end.
If the section is not intersected, nothing happens.
To extend, you need an
open spline. The end of the spline nearest the picked point is extended
until it reaches an intersecting spline. If there is no intersecting
spline, nothing happens. Curved splines extend in a direction tangent
to the end of the spline. If the end of a spline lies directly on
a boundary (an intersecting spline), then it looks for an intersection
As of version 3 of 3ds Max,
interactive trim/extend functions. The only reason to use this modifier
is to apply it at a specific location on the stack.
Before and after initial
use of Trim
Before and after second
use of Trim on above spline
Before and after using
To trim a shape using the Trim/Extend
- Create an open
Line shape in
the form of roughly concentric overlapping circles.
- Apply the Trim/Extend modifier.
- Click Pick Locations.
- Click the inner spline sections of the
concentric shape to trim them away, or click the open spline segment
to extend the spline.
- Pick Locations
Click to turn on Pick mode.
While in this mode, the mouse cursor changes in appearance when
over part of the spline that can be affected by the Trim/Extend modifier.
Click to either trim or extend the spline, based on the settings
Specifies the type of
operation that's performed on the selected spline.
When this is chosen,
a Trim is first looked for and, if not found, an Extend is attempted.
In most cases, a Trim will occur when Auto is chosen. An Extend
can occur, however, in cases where an open spline exists without
intersecting other splines.
- Trim Only
Performs only trims. Turn
on Pick Locations, and then click the spline section you want to trim.
- Extend Only
Performs only extends. Click
Pick Locations, and then select the open spline section you want
- Infinite Boundaries
For the purposes of calculating
intersections, turn this on to treat open splines as infinite in
length. For example, this lets you trim one linear spline against
the extended length of another line that it doesn't actually intersect.
NoteAs the number of
open splines in the shape increases, the chance of finding an intersection,
when using Infinite Boundaries, increases as well. This can produce
results you might not have expected because of projected spline
intersections you hadn't considered, particularly if you're in Auto
mode. For predictable results, avoid using Auto mode when using
These options specify
how the Trim and Extend functions determine a valid intersection.
Projects the lines onto the
active viewport, and judges the intersections accordingly. These
are the intersections as you see them in the active viewport.
- Construction Plane
Projects the lines onto the
current construction plane.
- None (3D)
Considers only true intersections
as the splines exist in 3D space. They must physically intersect
to be considered.