How to Create Circles, Arcs, Donuts, Ellipses, Splines, and Revision Clouds in ZWCAD

ZWCAD makes it easy to draw precise curves and round shapes for your CAD designs. In this guide, you'll learn steps to create circles, arcs, donuts, ellipses, splines, and revision clouds using different tools and options.

 

 

Creating Circles

Use the CIRCLE command to create a circle. A circle is made up of a center and a radius (or diameter)

To create a circle, you can:

• Specify the center (sphere center) and radius

• Specify the center and diameter

• Specify two points on the circle

• Specify three points on the circle

• Specify two tangent objects and a radius

• Specify three objects that are tangent to the circle

 

To create a concentric circle, you can:

• Specify the common center and the radius of each circle

• Specify the common center and the diameter of each circle

• Specify the common center, radius of the first circle, and how far apart the other circles should be from each other

 

 

Creating Arcs

Use the ARC command to create an arc. When you draw an arc, it is drawn in a counterclockwise direction by default.

To draw an arc, you can:

• Specify a start point, end point, and a point on circle

• Specify the start point, center, and end point direction

• Specify the start point, center, and center angle

• Specify the start point, center, and chord length

• Specify the start point, end point, and center angle (the distance between start point and end point determines the chord length of arc, and the angle of arc determines the degree of curvature of the arc)

• Specify the start point, end point, and tangent direction

• Specify the start point, end point, and radius

 

 

Creating Donuts

Use the DONUT command to create a donut.

To create a donut, specify the inside diameter, outside diameter, and center point.

• Inside diameter (hole size)
• Outside diameter (outer circle size)
• Center point (where the donut is placed)

If the inside diameter:

• = 0 — solid circle
• = outside diameter — the ring will form a line
• > outside — automatically swap with outside

 

 

 

Creating Ellipses

Use the ELLIPSE command to create an ellipse or elliptical arc. The curve shape of an ellipse is determined by its major axis and minor axis.

To draw an ellipse, you can:

• Specify the center point, major axis, and minor axis endpoints

• Specify three axis endpoints

 

For concentric ellipses:

• You need to specify a center point, major to minor axis ratio, and circumcircle radius.

• The Rotation option allows you to rotate a circle around an axis. To do so, you need to specify two axis endpoints and rotation angles.
• Execute the DSETTINGS command to turn on Isometric Snap in Drafting Settings. The ELLIPSE command can be used to draw isometric circles, which simulate 3D space.

To draw an elliptical arc:

• Create an ellipse by executing the ELLIPSE command
• Set the start and end angles

In the following figure, the elliptical curve between two angles is the elliptical arc.

 

 

 

Creating Splines

Execute the SPLINE command to create splines, curved lines that flow through or near a series of points.

You can draw splines by fitting points or control points.

Creating Splines by Fitting Points

Creating a spline through fitting points means the curve passes through specific points.

In the following figure, several fitting points are specified, and a spline passes through each fitting point by default.

 

Fitting Tolerance

Fitting tolerance controls how closely the curve follows the points (default is 0).

The smaller the fitting tolerance, the closer the spline curve approaches fitting points.

In the following figure, the fitting tolerance is 20.

Knots

Knot parameterization affects the curve shape.

In the following figure, the knot parameterization options for the red, gray, and green splines are chord, square root of chord length, and uniform, respectively.

Create a Spline Through Control Points

Control points are used to control the shape of spline.

In the following figure, several control points are specified to create a spline.

Degree

The degree of a spline means how smooth and flexible the curve is. The higher the degree, the more control points there are.

Spline Conversion

When you select a spline, its fitting points or control points will be displayed. You can use triangle grip to switch between displaying control points and fitting points.

 

 

Creating Revision Clouds

Use the REVCLOUD command to create revision clouds. Revision clouds are composed of continuous arcs.

Revision clouds are commonly used to highlight changes or important areas. For example, in file comparison, revision clouds are used to mark the differences between two drawings.

 

Approximate Arc Length

The approximate arc length specifies the approximate length of each arc on revision cloud, and calculates the minimum and maximum arc lengths.

Revision Cloud Conversion

You can convert specified objects to revision clouds, such as circles, polylines, splines, etc.

Draw Mode

You can draw revision clouds of rectangles, polygons, and any other shape.

• For rectangles or polygons: specify the vertices of rectangle or polygon
• For free drawing: move the cursor in drawing area, similar to freehand drawing

Revision cloud style

You can specify the revision cloud style as:

• Normal: zero width polyline
• Calligraphy: wide polyline with a different starting and ending width

The left figure is in Normal style, and the right in Calligraphy style.