Autocad 3d Draw on Z Axis
Topics covered in this Lesson:
3D Coordinate system | Rotation in 3D
The 3-D Coordinate System
By now you should be very comfortable working your way around the X-Y coordinate system. Anyway, here is a quick review. Looking from the plan view, this is what you see to figure out where is positive X and positive Y.
If you were to look at the same picture, but at a slight angle, you would see the third axis. This new axis is called the Z-axis. Imagine that the positive Z-axis is coming towards you out of the monitor.
The Z-axis has always been there, lurking in the background, waiting for you.
When you entered points previously, you would enter them in the format: X,Y. By doing this, you let AutoCAD know that in these cases, Z was equal to zero. Entering 4,3 would be the same as entering 4,3,0. Now if you drew a line from the origin (0,0,0) to a point at 4,3,2, you would get a line that goes 4 inches to the right, 3 inches up and 2 inches towards you. The properties of this line would be this:
Notice that the line is actually 5.3852" long. If you were to look at it from the plan view, it would look exactly like a line drawn from 0,0 to 4,3 Draw a line from 0,0 to 4,3 and then compare the properties.
The diagrams below, show this line from 4 different views to illustrate how things can look different in 3D. Look at each one carefully, and see if it makes sense to you.
What the above images show you is that you will have to get used to looking at a 3D world on a 2D monitor. In each image, the black line looks flat, but you have to use your reference points to determine where it truly is. If you don't understand this perfectly right now, don't worry. It's just an exercise to expose you to 3D viewing. As the lessons progress, you will get much more familiar to this.
Why is this important to look at before entering the world of 3-D? If you were to only look at a 3-D model from the plan (top) view, you would not be able to see any difference between the two lines. (Draw them and see for yourself) On a 3-D model, you can easily have many points over top of each other. This would be very difficult to work with. You may think you're snapping to a particular endpoint, but the reality of it could be very different (think of how the top of the wall looks the same as the bottom of the wall if you're looking straight down it).
Fortunately, AutoCAD provides different viewing options for 3-D drafting. This will be discussed in more detail during in a later lesson. For now, one way to change your view is to type in the VIEW command. It will bring up this dialog box:
Using the options shown above, you can see what the SW Isometric view looks like by selecting that choice on the left and then pressing the "Set Current" button. This will close the dialog box and change the view.
To get back to the top view, just start the VIEW command and choose "Top" from the list on the left and press "Set Current" again.
3D Rotation
Now for the confusing part. You already know how to rotate 2D objects, but you also have to know how AutoCAD measures angles of rotation in 3-D. There is a somewhat simple rule for this called "The Right Hand Rule". To figure out which is the positive rotation angle, imagine that you are wrapping your right hand around the axis with your thumb pointing towards the positive end. The direction that your fingers are wrapped is the positive direction of rotation. This applies to all three axes.
Direction of positive rotation using the right hand rule
The main point of this lesson is to tell you that objects can trick you in 3D space. Shortcuts don't always work, you have to be careful with Osnaps and your drawing can turn into a mess very quickly if you're not paying attention. Trust me, I've seen enough students take the easy route and have to start over. If you want to learn 3D, review each lesson before progressing. Make sure you know the concepts inside and out. This is just an introduction to the concepts, you will learn more in the following lessons. You may still want to refer back to this tutorial, though.
Video: Working in 3 Dimensions
Fun fact: AutoCAD R13 as the most hated release of AutoCAD when first introduced in November 1994. It was so buggy that the company soon shipped the first in a series of incremental updates in an attempt to quash the problems.
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Source: https://www.mycadsite.com/tutorials/level_3/view-rotate-3d-autocad-3drotate-3-3.html
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