Create Curves

What are Curves in Rhino?

Curves are the simplest form of geometry in Rhino. They are often the starting point for any 3D model. In Rhino, a curve encompasses lines, polylines, arcs, circles, conics and freeform curves. Any of these can be used as input for creating surfaces. Like any NURBS object, the shape is defined by its degree and control point location.

Curves are the starting point for most models. The shape is defined by its control points

Curves are the starting point for most models. The shape is defined by its control points

Linear Curves

Let’s start by using some of the commands that create geometry from straight segments.

To create segments:

  1. Run the New command.
  2. Select a template of your choice.
  3. Maximize the .
  4. Turn Grid Snap on.
  5. Run the Polyline command.
  6. At the Start of polyline prompt , type 0. The first point snaps to the Origin of the Grid.
  7. At the Next point of polyline prompt keep picking points by snapping to the Grid as you draw a profile shape.
  1. Right-click or press to end the command.
  2. Run the Line command.
  3. At the Start of line prompt snap anwhere on the grid.
  4. At the End of line prompt snap to another Grid intersection.
  5. Press to run the command again. Continue creating other lines at will.

Arcs, Circles and Conics

Learn how to create conic curves in Rhino

To create a pattern using conics:

  1. Change Layer to Layer 01.
  2. Turn Grid Snap on.
  3. Run the Circle command.
  4. At the Center of circle prompt , type 0.
  5. At the Radius prompt , type 20.
  6. Run the Ellipse command. At the Ellipse center prompt , type 0.
  7. At the End of first axis prompt , type 50 and click along the X axis (red).
  8. At the End of second axis prompt , type 30 and click along the Y axis (green).
  1. Run the Arc command.
  2. At the Center of arc prompt , type 0.
  3. At the Start of arc prompt , snap to the top of the ellipse.
  4. At the End point or angle prompt , type 90.
  5. Press to run the Arc command again.
  6. Create the second arc on the bottom side. As follows…
  1. Try it on your own! Use other commands like Rectangle or Polygon to add more details.

Freeform Curves

Freeform curves are the heart and the soul of Rhino. They allow you to place points in space and create a smooth shape in between. It is the way you define the shape of your product or model.

To use freeform curves:

  1. Change Layer to Layer 02.
  2. Turn Grid Snap off.
  3. Run the Curve command.
  4. At the Start of curve prompt , pick a point anywhere on the grid.
  5. At the Next point prompt , keep placing points randomly on the grid. Notice how it creates a network of points that contain the curve. The curve does not go through the control points.
Placing points far apart allow for a better curve flow.

Placing points far apart allow for a better curve flow.

  1. Right-click to end the command.
  2. Run the InterpCrv command.
  3. At the Start of curve prompt , pick a point anywhere on the grid.
  4. At the Next point prompt , keep placing points randomly on the grid.
Note how the curve goes through the points.

Note how the curve goes through the points.

Learn more about NURBS curves…

Curves in 3D

There are multiple ways of obtaining 3D curves. The main one is to use multiple viewports to draw the curve in 3D space.

To draw a 3D curve:

  1. Change Layer to Layer 03.
  2. Turn Grid Snap on.
  3. Maximize the viewport.
  4. Run the Curve command.
  5. At the Start of curve prompt , pick a point anywhere on the grid.
  6. At the Next point prompt , place two more points.
    Placing points in the Top viewport

    Placing points in the Top viewport

  7. Use the Viewport Tabs to switch to the and continue placing points.
    Placing points in the Right viewport

    Placing points in the Right viewport

  8. Switch to the and continue placing points.
    Placing points in the Front viewport

    Placing points in the Front viewport

  9. Right-click to end the command.
  10. Switch to the to view your 3D curve.

Curve Orientation

Curves are often the starting point for creating 3D objects in Rhino. When creating surfaces from curves, you will likely need sets of curves that are oriented parallel or perpendicular to each other.

To draw curves with different orientations:

  1. Change Layer to Layer 04.
  2. Turn Grid Snap on.
  3. Maximize or switch to the viewport.
  4. Run the Curve command.
  5. At the Start of curve prompt , pick a point anywhere on the grid.
  6. At the Next point prompt , place a few more points.
  7. Right-click to end the command.
  8. Right-click or press to run the Curve command again.
  9. Create a second curve on this viewport.
  10. Switch to the viewport.
  11. Make sure the End Osnap Control is enabled.
  12. Run the Circle .
  13. Select the 2Point option in the prompt .
  14. At the Start of diameter, snap to the end of your first curve.
  15. At the End of diameter, snap to the end of your second curve.
    Two sets of curves oriented perpendicular to each other

    Two sets of curves oriented perpendicular to each other

  16. Try it on your own! Run the Sweep2 command and follow the prompts to obtain your first 3D surface!
Learn more about creating surfaces from curves…