InterpCrv | Rhino 3-D modeling

Note: Many CAD programs use the term spline to describe an interpolated curve.

Steps

Pick the start of the curve.

Pick the next points.

Press Enter to end the curve.

AutoClose steps

Move the cursor close to the start point of the curve, and pick.

The curve will close.

Press the Alt key to suspend automatic closing.

When drawing a high-degree curve, the output curve will not be the degree you request unless there is at least one more control point than the degree.

Determines how an interpolated curve is parameterized. When the spacing between the picked points is equal for the whole curve, all three parameterizations generate the same curve.

When you draw an interpolated curve, the points you pick are converted into knot values on the curve. The parameterization means how the intervals between knots are chosen.

The knot spacing is always 1 and is not based on the physical spacing of the points. Uniform parameterization can be used if the point spacing is roughly equal and it is desirable to draw several curves that have the same parameterization. This is possible only with uniform curves (unless you rebuild the curves). Uniform guarantees that every control point affects the surface exactly the same way, no matter how much the surface is edited.

The spacing between the picked points is used for the knot spacing. This makes curves that have widely varying point spacing behave better than uniform curves.

The square root of the spacing between picked points is used for the knot spacing.

The PersistentClose option closes the curve as soon as there are two points placed.

Note: If you continue to pick points, the curve updates the shape while remaining closed.

Draws the start of curve tangent to another curve or tangent to a direction shown by picking a start and end direction.

Draws the end of the curve tangent to another curve or tangent to a direction shown by picking a start and end direction.