January 22, 2010

**Computing areas** is a function widely performed among the designers in the fields of **AEC** and manufacturing. Can the **area computation** functions of __ZWCAD__ meet the requirements of these designers? The answer is definitely “Yes,” and can be proved easily by the following examples.

1. Computing the Area of a Single Object

Areas can be found through three commands in ZW**CAD**: Area, List, and MassProp, Let’s look at each of them.

Ø Area Command

1) Draw a circle with a radius of 40 units.

2) Enter the Area command, and then follow the prompts to type E (for entity) to select the circle. The final result is displayed in the command prompt bar, as shown below.

Ø List Command

1) Draw a rectangle with sides of 100 and 80 units.

2) Select the rectangle, and then enter the List command.

3) When you press Enter, the final result is shown in the Text window (highlighted in the figure below).

Ø MassProp Command

1) Draw a hexagon inscribed in circle with a radius of 100 units.

2) Apply the Region command to turn the hexagon into a region object.

3) Use the MassProp command for a result like the one highlighted in the figure below.

Notice that this command finds not only the area of the hexagon but also its moment of inertia. (Note that the Standard version of ZWCAD does not include the Region command, which is provided with ZWCAD Professional version.)

The commands described above were used to find the areas of single objects. But what about calculating the total area of several objects?

2. Calculating the Total Area of Several Objects

The commands AreaSum, Area, and CalArea are used to sum the area of selected objects. Although they all appear to perform the same function, each has particular advantages and disadvantages. Let’s have a look.

AreaSum

1) Use the Polyline command to draw a closed polygon with a random outline.

2) Also draw circle with a radius of 50 units and a rectangle with sides of 100 x 200 units.

3) Select the three objects, and then enter the AreaSum command. The result is shown below.

This command operates simply: select several objects, and then input the command’s name (AreaSum) to arrive at the final result. But this command cannot be used to compute the area of a single object, and is limited to calculating the area of closed objects such as circles and rectangles. If the closed object is drawn with the Line command, this command will not work.

Area

From the screenshot below, we see that the Area command computes not only areas of single objects, but also the sum of several objects. The sum of the areas is listed correctly after following this operation:

1) As an example, let’s draw two circles with radius of 50 and 100 units.

2) Start the Area command, enter A (Add option), and then enter E (entity option). When you choose the larger circle, its area is computed.

3) Again enter A, and this time choose the smaller circle to get its area. When done, the total area is shown in the command bar.

How about subtracting one area from another? Here are the steps involved:

1) Restart the Area command, enter A (for addition), and then E (for entities).

2) Choose the larger circle, and get its area.

3) Press Enter to confirm.

4) Continue with S (for Subtraction), then E, and finally choose the smaller circle. From this, you get the difference in area of the two circles.

The steps above show how Area can be used to compute both the total and the net areas of objects. However, the many steps involved make it less than practical.

CalArea

The CalArea command is a more practical but is found only in ZWCAD Mechanical. Here is how to use it.

1) Draw two circles with radii 50 and 100 units.

2) Start the CalArea command, and then click any part of the 100-radius circle.

3) Right-click, and this dialog box appears:

From the figure, we can see how adding and subtracting areas involves merely clicking the Add or Subtract buttons. Let’s sum the areas of the two circles.

4) Click Add, then pick any place inside the 50-radius circle.

5) Right-click to see the result, as shown below.

6) Directly, we can also get the net area: just click the Subtract button.

From the screenshot, we see that the CalArea command can not only be used for area calculations, but also for determining the weight and specifying the material selection. For example, when we chose the material of Carbon Steel, the Density (kg/dm3) automatically adjusted to 7.8500. When we changed the Height (mm) to 100, again the weight updated automatically to 30.8269.

The above examples show how practical CalArea is, and so it is no wonder that it is popular among designers. But remember: the function is available only in the ZWCAD Mechanical, and not on the regular __cad software__.

To sum up, all five functions -- AreaSum, Area, List, MassProp, and CalArea -- show clearly that the area calculation function of ZWCAD meets the requirements of designers.

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