Draw a curve by placing CVs or edit points

Use the Curves > New Curves > New Curve (cvs) or New Curve (edit pts) tools to draw curves by clicking to place CVs or edit points.

Set up the New Curve tools

To set what parameterization and degree the curves you draw will have, open the tool’s option box and set the Knot Spacing and Curve Degree options.

Draw curves by placing CVs.

1. Choose Curves > New curves > New Curve by CVs.
2. Click in view windows to place the CVs of the new curve, or type coordinates for the CV locations.

   See Use the mouse and keyboard in tools.

   For a degree 3 curve (default), the curve will only appear after 4 CVs have been placed.

   NoteThe general rule is that a curve of degree m requires m+1 CVs before becoming visible. To see the curve sooner, turn on Progressive Degree in the option box.
   TipThe first CV in the curve is shown as a square and the second as a “U” instead of a cross. This helps show the direction of the curve.

   

3. Choose the tool again to start another curve.

Draw curves by placing edit points.

1. Choose Curves > New curves > New Curve by Edit Points.
2. Click in view windows to place the edit points of the new curve, or type coordinates for the CV locations.

   Use the mouse and keyboard in tools

   

3. Choose the tool again to start another curve.
   TipThis tool is useful when you want to create a single span curve from two end points.
   TipYou can continue drawing curves between view windows. For example, click the first point in the Top window, click the second point in the Back window, and so on.

What if...?

I want to add more points to a finished curve?

Use the Curve Edit > Modify > Add points tool.

Create a curve from a library of pre-drawn curves (sweeps)

The Sweeps tool lets you create a curve by pulling a curve from a curve library and transforming and trimming it.

The Sweeps tool is designed for use as part of a workflow: pick the curve from the library, transform it into place, trim it to the section you want, and set its pivot point. The user interface of the tool is optimized for these steps.

Create a curve from a sweeps library

1. Choose Curves > Primitives > Sweeps p.
2. The sweeps window has two tabs for a standard (site-wide) library and your own (user-defined) library. Click a sweep displayed in one of the tabs.
3. Click in a view window to place the curve.
4. Do any of the following:
   • Click Transform and use the transform manipulator to move, rotate, or scale the curve.
   • Click Trim to trim the curve (see below).
   • Click Pivot to move the curve’s pivot point (same as using the Transform > Local > Set pivot).
   • Click Create to create another curve using the selected library sweep.

Trim the curve

1. While using the Sweeps tool, click Trim.
2. Click to place manipulators at the start and end points of the section you want to keep.
3. A red arrow indicates which part of the curve will be kept. Click the other part of the curve to switch the red arrow.
4. Click Go to trim the curve, or click Transform, Pivot, Create, or another tool to cancel the trim.

Manage your sweeps library

Functionality relating to the maintenance of the sweeps library.

Open the library window

• Choose Curves > Primitives > Sweeps p.

Add curves to the user-defined sweeps library

1. Pick the curves.
2. In the library window’s Edit menu, choose Add Sweeps.

   All picked curves are added as individual sweeps.

Delete a sweep from the user-defined library

1. Click the sweep.
2. In the library window’s Edit menu, choose Delete Selected Sweep.

Save the user-defined library to a file

• In the library window’s File menu, choose Save Sweeps.

Add sweeps from a saved file to your library

• In the library window’s File menu, choose Import Sweeps.

Draw a blend curve

Blend curves let you create and edit curves by placing constraints on the shape of the curve.

Draw a curve by placing constraints

1. Choose Curves > Blend curve toolbox to show an extra floating palette containing the BlendCrv Tools tab.
2. Choose BlendCrv Tools > Blend curve create.
3. Click to place blend points.

   If you click on a curve, surface, or mesh, the blend curve is automatically attached to the geometry at that blend point (which is displayed with a slightly different icon).

   Use the mouse and keyboard in tools

   TipIf the tool cannot tell which curve you meant to snap to, it will show the . Point to the hand icon next to the curve you wanted to continue snapping to that curve.
4. Choose the Blend curve create tool again to start a new curve.

   Blend curves

Create a curve connecting objects

How to use different curve tools to draw a curve between existing objects, including continuity.

Connect two points with a blend curve

1. Choose Curves > Blend curve toolbox to show an extra floating palette containing the BlendCrv Tools tab.
2. Choose BlendCrv Tools > Blend curve create.
3. Click the first point.

   You can press the mouse button on a curve, surface or mesh, and drag the new constraint on it. Blend curves allow automatic snapping.

4. Click the second point.

The new blend curve automatically has curvature continuity when you snap to surfaces.

Connect two points with a basic curve

1. Choose Curves > New curves > New Curve by Edit Points.
2. Click the first point. You can use curve snapping to snap the point to a curve or surface.

   See Snap to curves, points, or the grid

3. Click the second point.

The new curve is a straight line between the two points. To make the curve tangent or curvature continuous, use Object Edit > Align > Align 2008 to align the new curve with the existing objects.

See Align, combine, or split objects

Add to an existing curve

Use Curve Edit > Modify > Add points to add CVs or edit points on to an existing curve.

Add CVs to an existing curve

1. Choose Pick > Point types > CV.
2. Pick the CV at the end you want to add on to.

   That is, pick the first CV to add to the beginning of the curve, or the last CV to add to the end.

3. Choose Curve Edit > Modify > Add points.
4. Click to add CVs.

Add edit points to an existing curve

1. Choose Pick > Edit point.
2. Pick the edit point at the end you want to add on to.

   That is, pick the first edit point to add to the beginning of the curve, or the last edit point to add to the end.

3. Choose Curve Edit > Modify > Add points.
4. Click to add edit points.

Add blend points to a blend curve

Edit or reshape a blend curve