UCS change or DVIEW TWIST?

[hdh500]

Hi all,

First time posting, and I hope I don't sound to naive. I've been using LDT3 for a couple of years now for stationing, cut and fill, sections, and profiles.

A recent thread had a comment about why you would change the UCS in a LDT drawing and I'm wondering what the general consensus is on the topic.

Quite a few times I am forced to change the UCS on my site drawings to make the area fit on a standard sheet size (24x36 or 30x42). When I have to do a LDT command I always have to make sure that my UCS is set at World. This is the only reason I see for changing the UCS. I'm not a fan of the DVIEW, TWIST option, I've gotten burned on that a few times.

Thoughts?

[mjfarrell]

My thoughts are Leave Model Space in WCS as this is the
real world we are representing.
In your Layout tabs, through the Viewport use DVIEW and twist.

In this manner the data in your Model Space will always look like
the real world, and on your sheets it will be rotated to fit the viewport
correctly. It does take a little getting used to seeing it one way in
the model and then flopped over on your layouts.

To label some items in model space it *may* be desirable to
create a UCS such that ones labels are plan readable.
The best practice when doing this is to always save and name
the UCS.
One could also temporarily apply a north rotation in the Drawing Setup
to accomplish this, and then after done with the labels, change it back.

[sinc]

One could also temporarily apply a north rotation in the Drawing Setup
to accomplish this, and then after done with the labels, change it back.
This is probably not a good idea..

If you only change the north rotation in the drawing setup, you'll screw up your drawing. The north rotation essentially rotates the N,E coordinate plane. This moves it away from your drawing objects.

Therefore, in order change the north rotation, you also have to turn on and thaw all layers in your drawing, and select and rotate all objects in your drawing by the opposite amount as you change the north rotation. That is, if you set a north rotation of 50°, you must then select all objects in your drawing and rotate them by -50° (310°). Otherwise, your linework will be at the wrong N,E and facing in the wrong direction.

For a variety of reasons, this process is not desirable. If you do it and you have a drawing with more than a few Cogo points, Autocad may crash/hang. You may also have various labelling issues. Not all text (i.e., curve text from Label Curve By Points) will move once created. Attributes in blocks may end up facing the wrong way. Dimensions may reformat themselves in undersireable ways.

There are ways around most of these issues, to be sure. For example, if your drawing contains more than a few Cogo points, you can first open your point options, and on the "Update" tab, check "Allow points to be MOVEd in drawing", and UNCHECK "Update points after MOVE". This helps keep Autocad from crashing/hanging. You can learn what causes the various dimensioning quirks, and thereby avoid most of them, or figure out a quick-fix. But grabbing everything in a drawing and rotating it makes everyone I know nervous, just on general principal. It's a dangerous edit operation that should not be used lightly.

I advise against using the north rotation in most situtations. It has its uses, but it causes a lot of problems (mostly with XREFs), and is generally best avoided. When it IS used, it should be thought of as similar to the drawing scale - it's something you set BEFORE you start to label your drawing, and once set, you generally don't reset it.

[tyeelaw13]

You don't want to physically change the ucs, then your coordinate system will be hosed. Dview is a good way to think about rotating the world to your view- rather than just the drawing. once you dview twist, it sometimes can be tough to get things to draw properly withougt setting your ucs to new and view. This way your crosshairs will change to your view, but won't effect the drawing in any way. Once you find that you want to go back to the "real world" view relative to the wcs, then just dview twist it back to 0. Then change the ucs to world, and you're back to the way the world relatively looks rather than having it rotated. I use to dview twist when i was setting houses for a surveyor. It was much easier to dview twist and change the ucs to new view rather than trying to work with the crosshairs not lining up with the way the lot looks.

[MHultgren]

I pprefer to work in WCS in model space and then set my veiw with DVeiw Twist option. I have a little macro that will set the crosshairs at the veiwtwist angle and back to 0 as needed. If I have to dimension something, I do that in paperspace to avoid the upside down dimtext problem. Labels go in MS as well as linework. We use xrefs to put our sheets together and by placing the dims in PS, we don't have to worry about having multiple layers for dimensions in different scales. We don't use more than one tab in a drawing so more than one peson can work on the project sheets at one time. I will OCCASIONALLY set a temp UCS for placing hatch patterns like Gravel and Concrete, but I think of any other time I would switch. I have another routine that prints out the twist angle so I can make sure that all my drawings are set to the same angle. I used to use one that had a box that showed your VPort limits with an X through it that you would pick to set the twist angle, but I got tired of seeing the lines running through my drawings.

[Baghera]

I pprefer to work in WCS in model space and then set my veiw with DVeiw Twist option. I have a little macro that will set the crosshairs at the veiwtwist angle and back to 0 as needed. If I have to dimension something, I do that in paperspace to avoid the upside down dimtext problem. Labels go in MS as well as linework. We use xrefs to put our sheets together and by placing the dims in PS, we don't have to worry about having multiple layers for dimensions in different scales. We don't use more than one tab in a drawing so more than one peson can work on the project sheets at one time. I will OCCASIONALLY set a temp UCS for placing hatch patterns like Gravel and Concrete, but I think of any other time I would switch. I have another routine that prints out the twist angle so I can make sure that all my drawings are set to the same angle. I used to use one that had a box that showed your VPort limits with an X through it that you would pick to set the twist angle, but I got tired of seeing the lines running through my drawings.
Mark,

Would you be willing to post the crosshairs macro?

[Aquaserpent]

You don't want to physically change the ucs, then your coordinate system will be hosed.

This is not totally correct, you have reset the origin to the vertex of the 2 lines used to create the new UCS.

Like I have stated in previous discussions on this issue, I develop my design in the world UCS, then when I am ready to annotate I will setup a polygon that represents the scaled area I will be documenting on each sheet in the plans. Then I create a UCS that is retaliative to the polygon and then name it. I then create a view of the polygon, while in the new named UCS, this process is repeated for each polygon that is not at the same orientation as another that has previously been created. After all views, named UCS, and annotations have been created I return to the World UCS to continue with the design efforts. Once I am ready to create my sheets I change my TileMode to 0 and insert a plan sheet. In the area setup for the view port I create one and then call-up a view into the view port. This process I have just documented gives me named views and UCS's that with a little planning are easily associated with a sheet tab name (ie. tab 03, will have PL03 and PR03 in the plan and profile view ports). The UCS name at this point is not relevant, however I can now call-up that orientation without calling up that view.

This whole process leaves the original World origin untouched and when I revert back to the World UCS my project coordinates remain the same as they were before I started this process.

[MHultgren]

Here is the code I use:


;;these are for osnap settings
(DEFUN C:OS0 () (prompt "\nOSNAP Mode reset to NONE")(setvar "osmode" 0)(princ))
(DEFUN C:OSE () (prompt "\nOSNAP Mode set to END")(setvar "osmode" 1)(princ))
(DEFUN C:OSI () (prompt"\nOSNAP Mode set to INSERT")(setvar"osmode"64)(princ))
(DEFUN C:OSN () (prompt"\nOSNAP Mode set to NODE")(setvar"osmode"8)(princ))
(DEFUN C:OSS () (prompt"\nOSNAP Mode set to 167")(setvar"osmode"167)(princ))
;;to set snap angle to 0
(DEFUN C:S0 () (COMMAND "SNAPANG" "0") (PRINC))
;;to set the snapangle to match the twist rotation of the VPort
(DEFUN C:STW () (setq snaprot (- 0.0 (* (getvar "viewtwist"))))(setvar "SNAPANG" snaprot))
;;to set the twist rotation to match the snapangle
(DEFUN C:TWS () (setq twrot (- 0.0 (* (getvar "SNAPANG") (/ 180.0 pi))))(command "DVIEW" "" "tw" twrot "" ""))

I save these in a lisp routine named Mytools.lsp that I load from the acad2000doc.lsp by adding a hook at the end of the file like this:


;; Load Mytools.lsp
(load "Mytools.lsp")
(princ)

[Baghera]

Thanks.....