Thursday

Command: _LENGTHEN

4 Comments Dec-04-2008 | Posted by Erhan Toker | Printable Version | Level |

We use this command to define length for an object.

Most of the time; we use TRIM and EXTEND for editing the lengths of objects. However, we  may wish to define the length of an object to a certain value. This is when the LENGTHEN command comes in handy. There are two main points that we need to note while using this command. You can define length for linear objects and define either length or angular distance for arc objects. Let’s take a closer look at defining linear lengths:

Fig.1 The larger grids are 50 units in size.

After our operation with the command, the new length of the line will become 150 units.

See how the command works:

Command: LEN
Select an object or [DElta/Percent/Total/DYnamic]:

Notice that there are four more options you can choose before selecting an object. They are:

Select an object or [DElta/Percent/Total/DYnamic]: DE
Enter delta length or [Angle]: -50
Select an object to change or [Undo]:

DELTA: Specify the amount of change you need (linear or angular) from the current state of the object. Use + to increase or – to decrease. Real simple. In my example, I entered -50 as the Delta value and then selected the line (Fig.1) to decrease the length of the line by 50 units.  In case you regret the changes, there is UNDO .

Select an object or [DElta/Percent/Total/DYnamic]: P
Enter percentage length <100.0>: 75
Select an object to change or [Undo]:

PERCENT: You can specify the magnitude of the change in terms of percentages. It is a ratio of the final length of the object to the initial length. Values greater than 100 increase while values lesser than 100 decrease the size. Remember that our line was 200 units in length. We user %75 in the command to achieve the same final length of 150. (150/200=%75)

Select an object or [DElta/Percent/Total/DYnamic]: T
Specify total length or [Angle] <1.0)>: 150
Select an object to change or [Undo]:

TOTAL: Specify the final Total length of the object, regardless of the inital value.

Below you can see a table comparing the various Lengthen methods for our example (fig.1)

Table.1

DYNAMIC: Can be used to specify the new length of the object by using the mouse. Very dynamic.

Our unit of measurement should be degrees rather than length units while working on arcs.

Fig.2

Arc lengths need to be defined in terms of angles as in Fig.2 In table.2 you can see the results of the various methods that can be used. We simply replaced the units in Table.1 with angles.

Tablo.2

You can use angles as an input method in every query under the Lengthen command.

Select an object or [DElta/Percent/Total/DYnamic]: DE
Enter delta length or [Angle] <0.0>: A
Enter delta angle <0.0>: 45

In our example, we used 360 degrees as a full rotation and as usual, counter clockwise was the positive direction for angle measurement.