Drawing circle is a basic operation in CAD designing just like drawing lines. The parameters for circles are simple yet different from drawing lines. The following are some common methods for drawing circles.

Two parameters are needed to draw circles: the radius and the center. The hard part is that we have to specify the location of the circle by its positional relation with other objects, such as tangency, that’s why drawing circles are different from drawing lines in many ways. You can see there are many options in the menu and toolbar to help you draw the circle you want, as shown in the following picture.

Given different elements, we can create circles with a center, radius, two points, three points, etc. With GstarCAD, you can also draw concentric circles.

Shortcut L is recommended when we draw lines, that’s because using the shortcut is faster than moving the cursor to click on the icon. But using a shortcut when drawing circles is another thing: We have to enter C in the command line, press Enter, enter the parameter and then press Enter again. Center and radius are default parameters, so if we know the value of them, then using shortcut will be faster. But there are exceptions such as tangency. Tangency has its icon in the toolbar, but it doesn’t have the corresponding parameter, in this case, we can only use the toolbar to execute this command.

We use some triangles to practice drawing circles in the following picture.

We can see the three circles are different to draw: for some of them, we know the center and radius while for others, we only know the radius and tangency. But how to exactly draw them, let’s explore more with the following steps.

- Enter C, press Enter to execute the circle command.
- Find the vertex of the triangle and click with the mouse to specify the position of the center.
- When prompted to enter radius or diameter in the command line, just enter 3 and press Enter to finish the drawing of an upper-right circle.
- Press Space or Enter key to repeat the command of drawing circle.
- Enter T, press Enter to use the method of tangency, tangency, radius.
- Move the cursor to the bottom, click to specify the first point when the tangent snap point shows, as shown in the following picture.

7. Move the cursor to one side, click to specify the second tangent point when tangent snap point shows.

8. When the command line prompts to enter radius value, enter 1, press Enter to complete the drawing of the second circle.

9. Click Tan, Tan, Tan button in the Toolbar, and snap the tangent point with the triangle one by one to complete the drawing.

Conclusion: Drawing circles is relatively simple and the key lies in what we know about the circles we are going to draw and choose the best method. We’ve also learned another skill: press Space key or Enter key can repeat our last command, which improves our efficiency.