Rotating objects

In rotating a geometric object, the program moves it from its original position to a new location by rotating it at an angle. Apart from rotating, the object can also be copied, which results in two objects: the original and the rotated one.

To rotate an object or a series of objects

1. Select the objects you want to rotate.
2. Do any of the following:

• On the Transformation toolbar, click Rotate .
• On the Transformations menu, click Rotate.
• Press CTRL+T+R.

A contextual edit bar appears above the graphical area.

Copy Leaves a copy of the original object.

Select Distance (Available when a center of rotation is set) Starts the mode for selecting the object whose angle will serve as reference in the rotation. For an example of how to use this functionality, see Example 2 and Example 3 below.

Step angle Rotates the objects at angle intervals equal to or divisible by the value. Leave empty if you do not want to specify a step angle.

Rot. Angle Rotates the objects at the entered angle value.

NOTE: The Rotate button appears only if there is at least one selected object in the drawing.

3. (Optional) In the contextual edit bar, click Copy to keep the original objects in place.
4. (Optional) In the contextual edit bar, in Step angle, enter an angle value. The objects will be rotated only by angles that are equal to or divisible by the Step angle value.
5. In the drawing area, click anywhere to define the starting point of the auxiliary axis in respect of which the objects will be rotated. This is the center of the rotation.
6. Drag the auxiliary axis to where you want it to be. It is displayed as an intermittent line, rotating the objects in respect of it.

7. Do one of the following:

• In the contextual edit bar, in Rot. Angle enter an angle value.
• Use the mouse to rotate the objects to where you want them to be.

8. Click to position the objects.
9. (Optional) To rotate the same objects around the same starting point, repeat Steps 3–9.
10. To exit the mode, press ESC.

Example 1: To rotate objects by using a reference line from the selection

During rotation the program shows relations between the axis of rotation and the rest of the objects. When we need to rotate a selection so that one of its lines (reference line) points in a certain direction — for example, to become horizontal or vertical — it is best to use the technique described below. During the rotation, we will make the axis of rotation and the reference object collinear; thus the relations the program indicates will apply also to the reference object.

1. Select the objects you want to rotate.
2. Do any of the following:

• On the Transformation toolbar, click Rotate .
• On the Transformations menu, click Rotate.
• Press CTRL+T+R.

A contextual edit bar appears above the graphical area.

3. (Optional) If you want to keep the original objects in place, in the contextual edit bar click Copy .
4. On the object, click the line that you want to use as reference object for the rotation.

The center of rotation has been set.

5. Press and hold down CTRL, and then click another point along the same object.

6. Release CTRL.

Now the axis of rotation is collinear to the reference line:

7. Using the mouse, start moving the selected group of objects. It begins rotating relative to the reference line.
8. Wait for the relation you are looking for, and then click. See an example of how you can do this:

We begin moving the mouse until we find the rotation position that we need. The mouse pointer indicators indicate the detected relations to the coordinate axes: parallel to the y-axis (left) and parallel to the x-axis (right).

Example 2: Rotating a selection by using a reference and target lines

The following example teaches you how to rotate a selection so that one of its lines (called reference line) becomes parallel to a line outside the selection (called target line).

We will rotate the hole so that its straight section (the reference line) becomes parallel to the box's crease line (the target line). Consider the picture:

1. Select the objects you want to rotate.

2. Do any of the following:

• On the Transformation toolbar, click Rotate .
• On the Transformations menu, click Rotate.
• Press CTRL+T+R.

3. Set the rotation center (the point of rotation).

Notice that the program automatically goes into the Detect Relations With Pointed-To Objects Only mode. In this mode, each pointed-to object — any object the mouse pointer goes through — is highlighted and its ends are marked by little cross marks (pictured).

HINT: To clear the set of pointed-to objects, press CTRL. As a result, the pointed-to objects are no longer highlighted and the cross marks disappear.

The center of rotation has been set.

We proceed by setting the reference angle, which we will use to rotate the selected shape. We will extract this angle by pointing to an object from the selection.

4. On the contextual edit bar, click Select Distance .
5. Press and hold down CTRL, point to the line that you want to use as reference, and then click.

IMPORTANT: Before clicking, wait until you see a little compass at the cursor (pictured). This type of cursor indicates that you are in the mode for extracting line angle.

The reference line is set. Notice that the rotation axis is now parallel to the reference line:

We now move to setting a target line.

6. On the contextual edit bar, click Select Distance .
7. Point to the line that you want to use as target, and then click.

IMPORTANT: Before clicking, wait until you see a little compass at the cursor (pictured). This type of cursor indicates that you are in the mode for extracting line angle.

NOTE: There are two positions the selection can take on to accomplish the task. These are visualized depending on where you click with respect to the middle of the target object.

8. To complete the rotation and exit the mode, press ESC.

Example 3: Rotating by using a virtual reference and target lines

This technique consists in the rotation of a selection by defining virtual reference and target lines. In this case, we will use two clicks (1, 2) to define a virtual reference line in the selection. We then proceed to make this virtual line parallel to another virtual line defined by two other points (3,4).

1. Select the shape.
2. Do any of the following:

• On the Transformations toolbar, click Scale .
• On the Transformations menu, click Scale.
• Press CTRL+T+S.

3. To define the center of rotation, click anywhere.

We proceed by setting the virtual reference line, which we will use to rotate the selected shape.

4. On the contextual edit bar, click Select Distance .
5. Press and hold down CTRL, and then click the two points (Points 1 and 2) that we will use to define the virtual reference line. We will use its angle as a reference angle.

IMPORTANT: Notice the graphics the cursor acquires while we click. For Point 1, the numeral 1 appears at the cursor, indicating that we are in the two-point angle-extraction mode. When next we click Point 2, a small numeral 2 appears at the cursor. This indicates that the definition of the reference line and the extraction of its angle have been completed.

The rotation axis has become parallel to the reference line defined by the two points we clicked in the selection:

Next we will set the virtual target line. We'll do this by two clicks.

6. Click Select Distance , and then click consecutively Point 3 and Point 4.

IMPORTANT: Notice the graphics the cursor acquires while we click. For Point 3, the numeral 1 appears at the cursor, indicating that we are in the two-point angle-extraction mode. When next we click the Point 4, a small numeral 2 appears at the cursor. This indicates that the definition of the target line and the extraction of its angle have been completed.

The program has extracted the target angle and rotated the selection so that the virtual reference line is now parallel to the virtual target line:

7. Press ESC to exit the scaling mode.