vpoint, list, vports, pan, chprop, hide, vslide, osnap, 3dface, zoom, transparent commands, pedit, undo, erase, oops
Begin by opening your model, using the open
In plan view, the four rectangles you have drawn seem to present simple figures. If you view them three-dimensionally, however, they will look quite a bit different.
* To obtain a view from the southeast (assuming the x axis to be the east-west axis), with a viewing position that will give you a 45-degree angle looking downward, type vpoint
As you can see, this isometric view makes the rectangles appear to be very irregular. They are, of course, in the sense that the corners have different elevations. You will also see that the Rect. B and Rect. D are not at the same elevation. Can you figure out why? When we copied Rect. B (a 3d polyline with each corner at a different elevation), we put its lower left corner at the elevation (z-value) of 0, but when we drew the original rectangle, we put the upper left corner at 0 elevation.
Rect. C looks very strange because its corners are at different elevations. Where are the labels? They are all drawn at an elevation of 0; so some of them look as though they are in the wrong place here. (There is a default value for elevation; that is 0 now, and it determined the elevation of the text, since we could only indicate the x- and y-values when we picked the point for the text. If you type elev or elevation, you can change that default - but please don't do that now.)
* Type list
* To see that, in plan view, the rectangles are still positioned as they were, let's divide the drawing window into two halves - AutoCAD calls them viewports. Type vports
* Select the viewport on the right, if it's not the active one, and then type plan
You will probably find that the figures are too close to the corner of the viewport; so you may want to use the pan command to shift your image so that the part you are interested in lies more nearly in the center of your drawing window. Just type pan
* Use the viewport containing the plan view, and select Rect. A by clicking on it with the mouse.
* Having selected Rect. A, you should now type chprop
* You are going to change the thickness of the lines; so you should type t
Observe the change in Rect. A, a change which is visible only in the viewport with the 3D view. The lines for Rect. A now have thickness (in AutoCAD's terminology); furthermore, these thick lines are treated as surfaces.
* To see that these thick lines are treated as surfaces, switch to the isometric viewport and type hide
Notice what is hidden. It now looks as if Rect. A is a box with no top or bottom. For all practical purposes, it is. (But the box should hide the text and does not. I don't know why.)
* To show more clearly how surfaces and lines differ in a 3D model, there is a prepared image for you to examine on the server. (You must download the file to see it - click here to download the file in .ZIP format while you're on line. Unzip it - the zipped file is called viewhl.zip and the unzipped one hlsurf.sld - and put it in the directory where your model is stored. If you are not on line while working on the model, you may want to go back to your networked computer to download the file. The tutorial does not depend on your seeing the image, but your understanding of 3d views may.) Type vslide
* Return to your model by typing redraw
The only surfaces we have made so far are on the sides of a hollow box, Rect. A. To give the box a top, you must make an explicit surface, using the 3dface command. Since you are going to use only existing points in the model to make this surface, you can tell the system that all mouse clicks are intended to find the end of the nearest line (easier than typing endpoint before selecting the point, as we did before, when you're going to do so several times).
* Type osnap
* To make the new top surface, type 3dface
* Type hide
* Since we've finished drawing the 3D face, we need to turn off the requirement that the system find the ends of lines; if we don't, difficulties can arise, as mentioned above. So type osnap
* This is a good time to save your work. Type qsave
* Since we've seen that thick lines make good surfaces, let's make the lines for Rect. B and Rect. D thick as well. Using the plan view viewport, select one edge of Rect. B and one edge of Rect. D (using the direct click method, not a window). Now change the thickness to 1 (the command is chprop, remember?).
* Now click on the other viewport and type redraw
* Type hide
One of the advantages of using a polyline is that it can be treated as a single entity; lines with multiple segments, on the other hand, are multiple entities. Polylines can be moved, rotated, colored, and altered in other ways with a single selection; lines cannot.
But polylines cannot have different elevations at different vertices. That's one thing that makes 3D polylines different. They can have a different elevation for each vertex. However, 3D polylines cannot have thickness. That's why you weren't asked to give thickness to Rect. C. That would not work. We can, however, add explicit surfaces (3D faces) to the basic rectangle with the 3dface command.
* Using either viewport (the 3D viewport is often best with complex shapes, but it can be confusing with a shape like this, one that has different elevations at the corners), find the coordinates of the northwest corner of Rect. C. To do that, type id
* So, type 3dface
* Then enter the coordinates of the first point of the new surface, 3.8,5.375,1
* Then, for the second point, type endpoint
* For the third point, type endpoint
* For the fourth point, type @0,0,1
Now, if you start with the correct corner, you should be able to make another 3D face for each of the other sides of Rect. C without knowing any coordinates but knowing that the last point will always be 1 unit above the third one. (Remember that typing
* Type hide
* Now change to the plan viewport and draw another polyline ( pline command)
* From point 9,0,0
* To 1,0
* To 1,9, and here type arc
* and then 9,9, for the end of the arc.
* Type close
ZOOM & PAN
* In the plan view you may not be able to see the entire new polyline; so type zoom
* Now use the list command; type list
PAN, ZOOM, Transparent Commands
The pan and zoom commands are valuable viewing aids, of course, but they can also be crucial ways of letting you see the appropriate part of a model while you are making a new figure. Sometimes, though, you can be in the middle of making the entity when you realize that you need to pan or zoom. In an earlier lesson, you used the command 'z to zoom in the midst of a pline creation. That's called a transparent zoom (I don't know why they call it that either); you can also use 'p to do a transparent pan, panning in the midst of another process. (The apostrophe before a command - many commands but not all - indicates to the system that it can interrupt the current process to perform the command and then return to finish the current process. Check the manual to see what other commands can be used in this way. Note that you can use the help command in this way; in fact, typing 'help
* You can edit a polyline in two ways. The easiest way is to click on it so that the "handles" show. The handles are the little blue boxes at the vertices.
* To move the southwest vertex of the last-drawn polyline, click on the handle so that it is solid-filled.
Now type @0,1
* The other way to edit a polyline is to type pedit
* Type e
* and then keep typing n
* Type m
*You can also add a new vertex to a polyline with the pedit command. Type pedit
* Type e
* and then type i
* To locate the point, type mid
UNDO, ERASE, OOPS
*Since we don't want the point you just inserted to remain in the model, type undo
You will be prompted for a response, with number being the default. The number you type will be taken to be the number of command operations to undo. Typing
* To erase the polyline, either type erase
Erase the polyline using one of the methods just described. Having done that, however, you have changed your mind
* so type oops
Oops differs from undo, because it is intended only to change the last command, and it applies only to a small group of commands, including erase. Undo is a far more flexible command.
Save your work by typing qsave
Then make slides of your current work. You will need two slides, because each viewport must be treated independently. Select one viewport, type mslide
Now return to a single viewport using the vports command. Make sure you have a plan view showing.
Time to stop.
End of Session Two