6 | Create Curves

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.

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.