Power Tip

From CADD Master Ray

When Left Is Right, Which Way Is Up?
 
My first column on 3D Drafting covers one of the key difference between CAD and 3D Drafting, the nature of directions.

In CADD, X is always horizontl, and Y is vertical. this is partly due to the fact that the coordinate system is constrained to a single plane, but actually has to do more with the fact that, for now anyway, you can't rotate the cursor.

In 3D Drafting, the cursor can face any old way. In fact there are several commands (KA, Cursor Align; KR, Cursor Rotate; KS, Cursor Standard; RR, Rotation Reset) which cause the 3D cursor to rotate, often independently from the drawing. This means that positive X might be to the left, right, up, down, or any other direction that you specify. Fortunately, and by design, this greatly simplifies the creation of most objects in three dimensions.

In contrast to the flexible nature of the coordinate system, there is another set of directions, used by several commands, which are absolutely rigid. Left, Right, Front, Top, and Under (bottom) are fixed with relation to the objects in your drawing, not the current cursor or display orientation.

If you draw a BOX, for instance, in OBLIQUE mode, the FONT will be parallel to the screen and closest to you, the RIGHT side will be on the right, the LEFT side on the left, the TOP on the top, and so on, as you would expect.

However, if you use a VIEW STANDARD to view the object from the BACK, the left side will now be on the right, and the right side will be on the left. This makes perfect sense if you take a cardboard box (in the real world) and paint the words TOP, UNDER, LEFT, RIGHT, FRONT, and BACK on each of the appropriate sides, and then walk around it or turn it around. The same thing happens.

When you perform a VIEW STANDARD: LEFT, you specify the left side of the object, NOT to the left of where you are now standing. As an Architect, I prefer a different terminology that might help you as well. I call the back NORTH, because it is initially facing toward the top of the screen. I then cal the right side EAST, the front SOUTH, the left WEST, and I usually call the top PLAN. I call the bottom a CHOISI, and it's usually too confusing, so I don't worry about it too much.

I then use the following macro commands, which I have added to my VIEW menu in 3D Drafting, to get me where I want to go from any view, centering on either the last point entered or the origin:


NORTH,VS,V,0,0,0;
WEST,VS,L,0,0,0;
SOUTH,VS,F,0,0,0;
EAST,VS,R,0,0,0;
PLAN,VF,0,0,0,VS,T,0,0,0;


The comands can be executed in any VIEW mode except Perspective, and will cause the specified orientation to face toward you. The PLAN macro is an exception, which automatically selects a flat view. Four more macros get you to the four principal elevations just as easily, from any VIEW mode:

NORTH ELEV,VF,0,0,0,VS,B,0,0,0;
WEST ELEV,VF,0,0,0,VS,L,0,0,0;
SOUTH ELEV,VF,0,0,0,VS,F,0,0,0;
EAST ELEV,VF,0,0,0,VS,R,0,0,0;


I see I have no space LEFT to put any more of what's UP in FRONT of you RIGHT now, but I'll be BACK next time, you UNDERstand, to help you stay on TOP of CADD and 3D Drafting.