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Ahhh.... Yes. Is it a Quote? An Editorial? or an AutoCAD Tip? Who cares!

NOTE: Several AutoCAD Tips and Editorials are exactly the same!

WARNING: Not all of the Tips etc. have been tested with AutoCAD® 2002 or above - at least not yet! Most of these tips being from my EBCD newsletters from years ago!

Please read the DISCLAIMER.

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SNAPANG controls the angle of, for one, the crosshairs and most importantly ORTHO. It controlled other aspects of the program, however being able to rotate the crosshairs/ORTHO is invaluable.

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Similar to SNAPANG, SNAPBASE is a control for a basic variable - in this case the point of origin for SNAP and most importantly the origin for HATCHING.

Continued Below....

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MIRRTEXT controls how TEXT is mirrored. The default in AutoCAD® for many years was for it to mirror TEXT like the world is full of ambulance paint job designers.

Just make sure to set MIRRTEXT to "0" and be done with it.

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A sure sign of an AutoCAD® novice is overly complicated drawings. Complicated on many levels. For example: too many text styles, layers, dimension styles etc.. And, most often of all -- too many entities. Now, you might be wondering how on earth could you have too many entities? You need a line to draw a line . . . don't you? Yes, more or less. The "less" is the important part of that statement. Here are a few rules to keep in mind:

  • use POLYLINES instead of LINES
  • use BLOCKS for repetitive objects
  • use SHAPES for repetitive simple objects

At first one doesn't think much about the fact that most of one's time working in AutoCAD® is spent making "selection sets", first selecting objects, and then using the REMOVE and ADD options to modify the selection set. But you do. Therefore, anything that speeds up the selection set process has an inordinate effect on speeding up your work.

After all, why select two or more LINES/ARCS etc. when you can just select one POLYLINE?!

Why use a half dozen LINES, ARCS etc. when using a SHAPE instead will save time and drawing size?

And last, but definitely not least -- why select possibly hundreds of entities -- when you can select just one BLOCK? This is much more efficient as far as making selection sets, and also, everything else being equal the drawing size will be smaller.

There are, of course, many other advantages to using POLYLINES, SHAPES and in particular, BLOCKS.


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A certain percentage of idiots in every class/office do not understand the importance of using OBJECTSNAP. From the beginning of my "career" as a Computer Draftsman I took it one step further using what I call "Zen ObjectSnap".

Always do the same task in the exact same way. E.g. copying or moving the TEXT entity that makes up a note on a drawing - use the same OBJECTSNAP, from point to point. That way you know that every line of TEXT, every LEADER etc. is in the exact same position in all of your drawings.

WARNING: This only works if you do the whole drawing! Even one other CAD person working on one of your drawings can screw this up!

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"Previous to the last, was the last previous!"
Eric Bailey

I am somewhat chagrined to admit that when I was a beginner in AutoCAD® it was a revelation when it occurred to me that there was a "ZOOM-Previous" and a selection set "Previous". This illustrates the fact that it takes experience to understand all of the possibilities of "LAST" and "PREVIOUS" -- especially in respect to selection sets.

  1. First of all, there is a "ZOOM-Previous", but not a "ZOOM-Last" -- because what would be "ZOOM-Last" is of course "ZOOM-Previous"!

  2. "LAST" is used in making selection sets to select the LAST entity created that is visible in the display area of the monitor.

  3. "PREVIOUS" is similar to "LAST" except it selects the previous object(s) or, in other words, the previous selection set.

  1. In addition to the basics listed above, there are many obscure little tricks to learn . . .

  2. If, after hitting "Enter", you realize that there was an entity(s) that you should have REMOVED or ADDED (or even that you issued the wrong editing command) -- just cancel the command and then hit "Enter" again to repeat (or enter a new command) your editing command and "Previous". This will have reselected the Previous selection set and you will be able to ADD or REMOVE entities as required.

  3. Most importantly and, possibly, the least obvious is "REMOVE-Previous". For example: MOVE some entities (this is selection set 'A') on top of several (hundreds?) other entities. Again, using the MOVE command, use a window to select selection set 'A' and the other entities, then issue -- "REMOVE-Previous". This will remove what you had originally moved (selection set 'A' ), not everything that you just selected! This is because a selection set does not become a "Previous" selection set until the current command is finished!

  4. Editing with GRIPS does not result in a Previous Selection set, the Former-Previous Selection set is in affect.

  5. A "Previous" after using MATCHPROP does not include the Source Object, unless you specifically include it while making the Selection set that will be MATCHPROP'ed

  6. BHATCH does not result in a Previous Selection set, the Former-Previous Selection set is in affect. However using the old HATCH command does create a new Selection set.

  7. The DDEDIT command does not result in a Previous Selection set, the Former-Previous Selection set is in affect, yet other dialogue commands do create a new Selection set!

  8. MPEDIT: has very interesting characteristics. MPEDIT creates a Selection set -- but only of the entities that are already PLINES and only if you answer "Yes" to the question "Convert lines and arcs to plines ?". In other words, LINES and ARCS that are changed into PLINES by the command MPEDIT are not part of the new Selection set !

  9. MIRROR: If you answer "Yes" to the question "Delete original objects ?" in the MIRROR command the newly mirrored entities will be selected by "Previous".

  10. WBLOCK: When WBLOCKing entities a "Previous" (after OOPSing the entities back) will reselect them. This will enable you to easily ADD or REMOVE entities as required to redefine the DWG file you have just created

  11. "Cannot re-enter AutoLISP": This error message after issuing the SSX command requires the use of "Previous" in order to do a "work around". Use SSX to select objects and then issue a LISP routine command NAME, using "Previous" to select what was selected by SSX. You may now revise the Selection set using ADD and REMOVE.

As you can see the permutations are almost endless, however the main thing to remember is that you must be aware of how AutoCAD® actually works! Only in this way will you avoid random lines, arcs, text etc. appearing all over what should be a pristine CAD drawing.


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Although AutoCAD® usually works logically -- there are exceptions. For example, one would think that the selection set option "LAST" would select the last entity created in the drawing file. However, what it actually does is select the last entity created that is visible in the graphics display.

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Play with BLOCKs....
Eric Bailey

BLOCKs are one of the most powerful features in AutoCAD®. It is unfortunate that so little time is spent exploring their use in schools and offices. When I was in school it was mentioned in the same context as the COPY command – mainly as a way of drawing something once and then reusing it over and over. Specifically, it was mentioned in concert with the WBLOCK command as a way to create a block library. A very important feature.

However, the real power inherent in BLOCKs is to use them as an editing tool. Having INSERTed a number of BLOCKs into a drawing, you are free to edit, redefine for example, the BLOCK as required. Of course, in AutoCAD® 2000, you may do this very easily using the REFEDIT command! XREFs are a whole other subject (although almost identical to BLOCKs, XREFs are much more complicated from a CAD-managers perspective).

Try this exercise: Create a BLOCK consisting of one vertical line. ARRAY (or COPY etc.) the BLOCK along a line that represents the finished grade. This creates a simple "fence". An ugly fence, but a fence. However, because it was drawn originally by using a BLOCK, you can easily redefine that BLOCK to create the vertical boards and horizontal structure of an actual fence, with all horizontal lines matching, all (standard) details complete. If you use "BYBLOCK" and "LAYER 0" you may also control the COLORs, LINETYPEs etc. of your BLOCKs.

In particular, for Beginners, if you open a drawing that is filled with BLOCKs – do not EXPLODE them in order to edit them one at a time. First, explore the options/tools to automate the editing of BLOCKs, e.g., REFEDIT, basic redefining, Express/LISP routines that will SCALE or ROTATE etc. the BLOCKs and/or ATTRIBUTES for you!

EXPLODE a BLOCK to edit it only as a last resort. In other words - Play with BLOCKs....

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POINT. My point being, do not draw with points. Many people with little or no training in AutoCAD® think that they are being clever by using a POINT to draw a "point". However, a POINT's appearance can be more than just a "dot".

Points "locked" into a block is a whole other topic Note that POINT size is controlled by the variable PDSIZE.

No, it is much safer to just draw a really short line and make a block out of it. Ideally, draw a line say, 0.00000001 mm long, scale it by 0.001., and create a block out of it. Remember to set the colour of the LINE to BYBLOCK. Use MIDPOINT for the insertion point of the BLOCK. This will plot as a dot no matter what PDMODE is set to. PDMODE determines the appearance (e.g. line, circle, cross etc.) that points will have.

NOTE: Because of variations in computer setups, AutoCAD® releases etc., please do not assume that all of these tips will apply to your specific situation.

Please read the DISCLAIMER.

Click here for Editorials ~ including a number about AutoCAD and Computer Drafting.NOTE: Several AutoCAD Tips and Editorials are exactly the same!

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