XREF's, BLOCKs & other Disguised Stuff

I receive files created by others with which I must work with
individual layers of objects to do my job.

Sometimes I get a lot of info. that was drawn then put into a single
BLOCK (I guess).

Sometimes everything is on a layer that is an XREF ???

Sometimes I can select and explode a block in Autocad, save it and
then load it into the program I use. Then a single block with
everything in it gets separated into its individual layers before
leaving Autocad.

Sometimes I can load it first, and see that the blocks are already on
individual layers, and then I select all explode them in the program I
use, and I can then work with the data.

Sometimes I can see the data I want - text blocks of spot elevations
in ACAD for example - but I cannot figure out with my limited Acad
knowledge why these do not get passed on in the software I work.

Is there anywhere I can find an explanation of why and how these items
are not just plain old drawing entities that I can work with?

How many ways are there to make things difficult to work with?


Happy Trails To You

 

Also, I am told that Acad can keep some info - like points elevations,
or text describing these - in "attribute" databases? using MS Access
databases - what topic in the help can I look at to discover if this
has been done, or will there exist somewhere - hopefully in the
transmitted files, an Access database file with this stuff in it?

Happy Trails To You

 

See comments interspersed below:

The LIST command will clear up any confusion about what it is.

A "layer" is not an "xref". See help for both. The insertion of an XREF is
on a layer, and an XREF can have objects within it which are on the same or
other layers.

What program do you use? Does it have one item per layer?

What's that mean?

What's plain and old? The smartest way to structure a drawing may baffle you
today, but that doesn't mean it is wrong. There are advantages to be had by
adding complexity to CAD files, as long as the structure makes sense for the
given job, and that everyone who works on it understands it. If the drawing
is being used by different people for very different purposes, it could be
that the chosen structure of the file might not suit every equally. That
sounds like your situation.

Depends on the skill of the operator, and the tools at their disposal.

 

Michael,

Thanks for taking the time to respond.

My questions were prompted by a desire to learn not so much "what" it
is I am dealing with, but "why". Why would someone take a complete
drawing with building outlines, curbs, parking areas, serwers and
water mains, etc etc etc, and cram it all into a single block instead
of just leaving it as it was created - a bunch of lines, arcs, points
& text on separate layers of a drawing.

One I worked on a couple of weeks ago had the single block of all
drawing objects placed on a layer called XREF - hahahahaha.

Why would someone do that? I do not know enough about the workings of
Autocad to answer this question myself, so I asked the group here.

Terramodel - any number of items per layer. And infinitely more user
friendly methods of quickly displaying what various drawing objects
are (opinion/fact?).

Sometimes I load a drawing first in Tm, then explode it - sometimes I
have to run it through Acad to explode things, then import the result
into Tm.

By this I mean individual drawing objects on their respective layers.

I was hoping for a bit of explanation of exactly what these
complexities might be in Acad - not an acknowledgement or
justification of their existence.

Why and when does one use an Xref?

Why and when does one put a complete drawing into a single block - to
archive it? Or to pass it on in a slightly more compact, or ,more
obscure format?

If you considered "your" skill level, and the "tools" you normally use
every day in Acad, would it be possible for you to state briefly what
these might be?

I personally think someone would have to be a completely
non-co-operative obstination (I know it's not a word) to do some of
the stuff I see - but I'm willing to allow that there may be a good
reason for it that I just do not see.

I'm posing these questions here to find out.

Since posting a coupla hours ago I have fooled around extensively with
the layer manager in Acad, and also used the attribute extraction tool
to create several files of points which I have then edited slightly
and imported into Tm onto different layers - existing grades, proposed
grades, manhole & catchbasin tops, building FFE's, etc., so I'm having
a good afternoon, with a little help from you guys.

By monday I'll have some DTM's to load into my company's automatic
grading system, which is why I do this stuff.

- Tom

Happy Trails To You

 

In the case of an XREF, it's usually because someone wants to refer to a
drawing that is being worked on by someone else and/or is likely to change
before the project is complete. The XREF updates itself everytime the host
drawing is opened. It makes working in teams on the same project easier.
Blocks have to updated manually. Entities scattered everywhere would require
tedious repititious editing of every file in which the change occurs.

; P I do that sometimes. Usually with land surveys, or base-building
drawings.

The decision to this or that is situational. Only the operator will know why
its that way.
We can only guess.

See above. Are you sure it is an XREF? It could be a "plain old" block.

It's not more compact. Maybe they "blocked out" what they wanted you to
have, instead of deleting everything they didn't.

In acad, there's not much that puzzles me anymore. If I had to work on newer
platforms, I maight have a bit of a learning curve on some of the newer
features. Of course, someone could do structure something in a way that is
frustrating for my purposes, but if it was warranted, I would just
restructure the file. Luckily, I don't have to deal with others' CAD
drawings very much anymore.

It could also just have been expedient, or stupid. I'll never know from
where I sit. Just be advised that it is a common reaction to be frustrated
by the work of superior draftsmen when you are at the journeyman stage. All
I'm saying, is keep an open mind.

 

A lot of the things you seem to be encountering have to do with how
someone else organizes their work. Blocks, xrefs, templates and macros
are some of the powerful tools drafters use to avoid having to draw the
same thing over and over. Once a drafter/designer gets settled into a
position, there is usually a certain degree of repetitiveness to their
work - or at least some parts of it. The creative user will streamline
their workplace and add greatly to their effectiveness by using some of
the tools built into AutoCad to automate these tasks.

Ploughing through someones else's shortcuts to figure out what they were
doing and why can sometimes be confusing, even for experienced
operators. In your case, it sounds like you would benefit from looking
at the way the drafters of the drawings you inherit used these tools,
and trying to emulate them. Look in AutoCad's help menus, and in third
party texts - you may end up learning some tricks that will help you
enhance your own efficiency. the nice part about most AutoCad automation
routines is that they are relatively easy to learn, and give benefits
immediately, with a progressive learning curve.

 

While it is true you can often learn things very quickly by looking at
the way others do things, I would however rather educate than emulate
many of the draftsmen that supply the stuff I need.

The biggest fault I find, which I expect will change with more people
using LDD, is that in the fabrication of tin's, which other software
processes very quickly using 3 3D points per triangle, Acad designers
always seem to use 3 3d faces (lines) to describe each triangle,
requiring more than twice the data to describe, semmingly slowing down
the potential processing speed for these.

All software that I know of that forms tin surfaces from Acad designs
ends up throwing away the thousands of duplicated points in completing
this task.


Happy Trails To You