Clients teach me new things nearly every day. This week the lesson I learned is the difference between using DVIEW to rotate your design on screen and rotating the UCS about the Z axis. All of my CAD career, I've used DVIEW. For a long time, when someone mentioned rotating the UCS in a 2-D drawing I would cover my ears and go "Llalalalalalalala." Before this week, all I knew is that rotating the UCS caused major problems in survey software.
The company I trained this week had always used the UCS to angle designs into a more comfortable drafting mode. After telling them that they should use DVIEW instead, they naturally asked, "Why?" At a loss for a real reason, I've taken it upon myself to dig deep and understand what the difference is.
A little background…
UCS stands for User Coordinate System. When you first enter a drawing your UCS lines up with the WCS. WCS stands for World coordinate system where Y is up, X is right and Z pops out of the screen at you. WCS is a nice, normal place, where things don't go wrong. In any new drawing, the world coordinate system lines up with the user coordinate system, much like a rectangular piece of paper whose edges line up with the edges of the desk it is sitting on. Rotate the piece of paper and you are rotating the Coordinate system. If instead you just started working on the drawing by scooting your chair to another position, that is more like what DVIEW > Twist does.
DVIEW > TWIST & SNAPANG
DVIEW is accessed by typing DVIEW at the command line. (Shocking, I know.) DVIEW stands for dynamic view, and represents the position of your eye (or in Autocad terms, the Camera) in relation to the canvas. After you start the DVIEW command, you are prompted to select objects or select a DVIEWBLOCK. I usually go for DVIEWBLOCK unless I'm just going to eyeball the rotation with a line or two as reference for the rotation. Type TW for twist and key-in your rotation angle. A positive angle will rotate the camera counter-clockwise.
You can leave the drawing as is, but your cursor will have rotated too. I usually use SNAPANG to untwist the cursor back to parallel with the bottom of the screen.
Rotate Coordinate System
To rotate a coordinate system, use the view tab and find the Z axis rotation. Enter the angle you wish to rotate the view.
Rotating the UCS is redefining where the zero angle is, therefore a positive angle will rotate the coordinate system clockwise.
PLAN <CURRENT>
Like DVIEW, the rotated UCS leaves you with a wonky cursor. Key-in PLAN, then hit enter for Current to straighten things up.
Un-twisting
To un-twist from DVIEW, I type in PLAN, then W for world. (If you know of a slicker way, drop me a comment). To untwist a UCS, click the world button on the View tab.
Now that I understand the differences, I totally understand rotating the UCS if lots of text is going to get placed relative to the rotation. However, that is the only compelling reason to do it. Overall, I still recommend DVIEW over rotating the UCS. A drawing can only have one UCS at a time, but you can use DVIEW in every viewport if you wanted to. A rotated UCS can seriously impact how XREFS line up and how blocks are inserted. A rotated UCS will cause XREFs and blocks to come in at unexpected locations - you are changing the coordinate system after all!
DVIEW (Pros)
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UCS (Pros)
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Different dview twists can be set in different viewports
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Text placement follows UCS
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Works better when XREFS and blocks are inserted
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Can use cad objects directly to set angle (DVIEW requires you to measure first)
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Can be used in multiple viewports
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Preferred method for many 3rd party apps
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So next time one of your co-workers insists on rotating the UCS, you don't need to cover your ears and spout nonsense words. Get the whole story - then decide!
-HUGS, Lou
PS: Sign up NOW for my AU class Civil 3D for Beginners. November 29, 2011 1:00PM. Only a few spaces left! (Also, I bring candy.)
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4 comments:
I tend to rotate the UCS around Z when getting setting up the viewport views for plotting.
I'll look at the DVIEW command now though - good lisp here http://civil3d.wordpress.com/2011/10/04/rotating-your-view-without-changing-coordinate-values/
Rotating UCS does not scare me. You just have to be more aware of what your UCS settings are before you insert or xref other content.
One particular thing that I do all day is to set the UCS to "View" which is a newer option. This way text, multileaders, dimensions, etc. come in oriented to the viewport.
We have two basic Lisp routines - "UCV" changes the UCS to view; "UCW" changes it to world. Although it is pretty simple even without those.
All this to say - don't be afraid of changing UCS. It is not scary once you fully understand what is going on.
I like to use the vprotateassoc settings to adjust my viewport rotations. I rarely rotate in modelspace, I mostly rotate viewports only, so this method works good for me.
Rotate my viewport with the settings at 1, view rotates with the viewport, then set it to 0, and rotate it back. The viewport holds the new rotation. I sometimes grip edit the viewport back to the shape I'm after without adjusting the vprotateassoc setting.
You Have a lot to learn about UCS. I have used them for over 20 years for Plan/profile sheets. I create the desired UCS angle for my plan view, go to paper space create the vport. Set the vport to the UCS. Zoom to the correct scale. Lock the vport. return to model space and set the UCS back to WCS, and leave it there. When I need to add text I do it through the vport. This way model space is aways in world the WCS and my text always aligns with my view ports.
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