May 03, 2011

By Michelle Nico, a CAD software user

As a ZWCAD user, you use the Zoom command many times daily in your work. You may use it by double clicking to zoom the drawing to its extents, or else employing a favorite Zoom option, such as Window or All. Below, I’ve illustrated the initial prompt displayed by the Zoom command:

Have you ever notice the first line? It holds two options for specifying a special type of zoom scale factor. You may well be wondering how to use them, and what the difference is between them. Until a few days ago, I was also confused, but now I have worked it out. I’d like to share the results with you.

Firstly, there is no difference between them in how they operate in Model space. That’s because both are intended for use in paper space.

• nX sets the zoom scale factor relative to the current view.

Here is an example to help you understand it more clearly:

a. First, I drew a rectangle (shown in blue) in layout space, and then zoomed it to fill the entire viewport (shown in black).

b. I entered the Zoom command, and then typed 0.5x. This makes the rectangle look half the size, relative to the original.

• nXP sets the zoom scale factor relative to paper space.

This can be a little bit difficult to understand, right? OK, so here is an example to help you out:

a. Take the same rectangle, and zoom it to the extents of the viewport.

b. Enter the Zoom command, and then type 0.5xp at the command line. The result looks like the figure below. Notice that you can no longer see the entire rectangle.

c. The differences now look clearer to you, but you still might not understand the mechanism. To make things even more clear, I added dimensions to the viewport and the rectangle.

d. From the dimension values, we see that the rectangle is much larger than the viewport. Let’s work out the horizontal and vertical ratios:

The ratio of the lengths is 205.6/590.38, about 0.348.

The ratio of the widths is 156/264.19, about 0.59.

Here is my point: to view the whole length of rectangle, we need to zoom the rectangle to 0.348 or smaller; to view the entire width of the rectangle, we need to zoom to 0.59 or smaller.

Thus, we need to set the scale factor to 0.348 or less (let’s say 0.34) to view the entire rectangle – both width and length. After entering 0.34xp and pressing Enter, we see the result, as illustrated below:

The nXP option lets us zoom models in paper space at a ratio relative to the viewport:

n – indicates a number.

X – indicates relative zoom

P – indicates paper space

(If you cannot see the whole rectangle, then use the Pan command to position it correctly within the viewport.)

If you have any tips on using ZWCAD, don’t hesitate to share with me!