Creating Free Form Curves on Surfaces

You can create free form curves on a surface: Free form curves passing through all the points you select, or isoparametric curves. The curves must lie on the surface, but do not need to divide it.

This task shows you how to:

Before you begin: Open an existing 3D shape that contains a surface.

Create a Curve Point by Point

You can create a curve on a surface by joining from point to point.

  1. From the Creation section of the action bar, click Curve on Surface .
  2. In the Creation Type area, select Point by point.
  3. In the Mode area, select the curve creation mode.
    • Through points: Creates a multiarc curve passing through each selected point.
    • Near Points: Creates a single-arc parametric curve with a specified order and smoothed through the selected points.
    • With control points: Creates a parametric curve with the selected points as the control points.
  4. Select the surface on which the curve to create and click the start position of the curve.
  5. Click as many locations as you want the curve to go through.

    The curve is previewed as you move the cursor.



  6. To modify the shape of the curve during its creation, move the cursor to a control point and drag the handle.


  7. To edit the position of a control point or keep a record of its position, right-click the control point and select Edit or Keep this point.
  8. Double-click or click OK to create the end point of the curve.
    Note: You can toggle trough the 3 modes after the curve creation.

Create Isoparametric Curves

You can create isoparametric curves on a surface, in both U and V directions.

  1. Click Curve on Surface .
  2. In the Creation Type area, select Isoparameter.
  3. In the Mode area, select Manual selection.
  4. Select the surface on which you want ot create the curve.
  5. Move the cursor over the surface and click to create a curve.
  6. Move to a second position and click to create a second curve.


  7. Optional: Right-click and select Invert Parameter to inverse the direction of the curve.
  8. Click OK.
  9. In the Mode area, select Automatic selection and repeat the above steps.
  10. Enter values for the number of isoparametric curves in the U and V directions.


  11. Click OK.

Create a Tangent Curve

You can create a tangent curve on a surface.

  1. Select the With control points mode and click the first two points on the surface edge (parametric line).


  2. Continue creating the curve as described above.
  3. If you want to make it tangent on both sides of the surface, proceed by clicking two points on the other edge.


  4. Click the last point on the surface edge.
    This is especially useful when breaking a surface. The surface edge presents a tangency continuity.

The resulting curves always lie on the surface, even if you modify them using the control points capability after creation time.