# Spline in AutoCAD

**Spline in AutoCAD (easy)**- a smooth Bezier curve, which by default runs through given points, or deviates from them within tolerance.

or

**Spline in AutoCAD (complex)**- is a piecewise smooth polynomial curve NURBS (NURBS - Non-Uniform Rational Bezier Spline) - nonuniform rational Bezier spline - Bezier curve, as a special case of the B-spline, passing near a set of control points.

## Properties spline in AutoCAD

In AutoCAD, there are several types of splines, but they all have similar properties.

Spline divided into segments (similar polyline), called knot. If the nodes (segments) are unevenly distributed along the spline, the spline is called nonuniform B-spline.

To shape the spline using fit points and control vertices. Defining the default points are on the line, and the top of the control - outside of it.

Order spline defines how many times the curvature of the spline can be changed within a single segment. The curve of the first order - a straight line. The curve of the second order has a constant curvature (arc). By default, a spline curve is a combination of polynomials of degree-3 segment (also called cubic curve - may be one change in the curvature of the curve segment of the fourth order -. Two changes, etc, you can bring the value to 10.

## Command Spline

Responsible for the construction of a spline in AutoCAD Spline command. That you can call:

- Draw lines from the menu - Spline line in the drop-down list of two lines with a choice of ways to build: Spline Fit and Spline CV;
- Home tab of the ribbon tools - in a group Draw - two buttons with a choice of ways to build: Spline Fit and Spline CV;
- toolbar Draw - Spline button;
- or to register the name of the team in the Spline command line.

## Building a spline in AutoCAD for defining points

Call Spline command from the command line. prompted the command prompt:

Specify first point or [Method/Knots/Object]:

The current settings are also displayed in the command line: method = Sets, Units = chord. Select the first defining point of the spline. By default, it displays the dashed yellow line that will follow from the first defining point-cursor to a crosshair. AutoCAD prompts you:

Specify next point or [start Tangency/toLerance]:

If you want to ask a touch at the starting point, then select the option at the beginning of touch, because after specifying the second point defining this option is not available. We point coordinates of the second point defining the spline click in the drawing. AutoCAD will trace portion of the spline and display the dashed line is yellow, which will be followed by a second determining point-cursor to a crosshair. AutoCAD prompts you:

Specify next point or [end Tangency/toLerance/Undo]:

We take the following decisive point of the spline. AutoCAD prompts you:

Specify next point or [end Tangency/toLerance/Undo/Close]:

After specifying a third point defining appeared Close option that closes the spline.

You can choose toLerance option that lets you change the precision of the stroke determining spline points (does not apply to the extreme points). Tolerance value 0 builds spline curve that passes exactly through all the control points. The tolerance value is greater than 0, builds a spline curve that passes the vicinity of the reference points within tolerance.

Touching option at the end allows you to specify the condition of tangency at the end point of the spline.

press "Enter" to complete the construction of a spline in AutoCAD.

## How to build (make) a spline in AutoCAD various mathematical methods

Splines in AutoCAD are constructed with mathematical precision. Building a spline by defining points Knots includes an option that allows you to choose mathematical methods for constructing spline. Mathematical methods for constructing spline determine how components are combined curves between adjacent determining points on the spline.

Chord. (The method for determining the length of the chord). Accommodation units, connecting each component curve is proportional to the distances between each associated pair of defining points.

Square root. (Centripetal method). Placing nodes curve connecting each component proportional to the square of the distance between each associated pair of smoothing points. This method usually produces "softer" curves.

Evenly. (Equidistant method). It places the nodes for each component of the curve at an equal distance from each other regardless of the distance between the points of smoothing. This method often produces curves lengthening defining point.

## Building a spline in AutoCAD for control vertices

Call Spline command, then select the Method option - CV. At the command prompt, you are prompted:

Specify first point or [Method/Degree/Object]:

Specify the first point of the spline click in the drawing. By default, it displays the dashed yellow line, which will stretch from the first point to the cursor, crosshair. AutoCAD prompts you:

Enter next point:

That is, we need to specify the coordinates of the first control vertex spline, because said first point is not. When using the method of construction of the spline on top of the first control point and end point of the spline set defining points. Define the control vertex spline click in the drawing. As soon as we give the top management, displays a thumbnail of the spline, which will stretch from the first defining point-cursor to a crosshair. The dashed yellow line will extend from the top to control the cursor, crosshair. The dashed line is displayed in white, which begins in the first defining point of the spline, and passes through the specified control vertex spline to a crosshair cursor. AutoCAD will issue the following query:

Enter next point or [Undo]:

Specify the following control vertex spline click in the drawing. The dashed yellow line will stretch from the last specified control vertex spline-cursor to a crosshair. The dashed line of white color will start at the first point defining the spline and passing through said apex to control the cursor crosshairs. Sketch spline will also extend from the first defining point to the crosshairs.

Notice how the spline is constructed by control vertices (a special case). The dashed line of white color, connecting the top of the control forms a broken line. Spline broken line inscribed in and passes through the end vertices of the polygon, as well as through the midpoints intermediates polygonal spline inflection in the case in those areas.

prompted the command prompt:

Enter next point or [Close/Undo]:

Let us end the decisive point of the spline click in the drawing. press "Enter" to complete the Spline command.

## How to convert a polyline into a spline in AutoCAD

Spline in AutoCAD command with the Object option allows to convert two-dimensional or three-dimensional polyline to a spline.

If you want to convert a polyline into a spline without anti-aliasing, then select the Method option - CV (the construction of a spline by control vertices).

Converting a polyline to a spline by defining points without antialiasing impossible.

## Video "Spline in AutoCAD" (Russians)

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