Wednesday, January 11, 2012
Where do AutoCAD Dimensions Belong? Paper Space or Model Space?
There are some topics that will always be debated; Paper or Plastic, Mac or PC, Football or Soccer, Standard Time or Daylight Savings Time, Dimension in AutoCAD’s Model Space or Paper Space?
The problem with this question is the same as with the other questions that I mentioned, the answer depends on what you are doing. That answer sucks to be honest, but it’s the truth. Many times it really won’t matter. Other times having dimensions in model space is the worst thing to do! Or the worst will be having a million dimensions in paper space across several tabs that have to be updated when one model space dimension would have updated everything.
When is dimensioning in Model Space ok? When that dimension (and this goes for text too) needs to be shown everywhere (or nearly everywhere) or when there will only be one paper space tab in the file.
When is dimensioning in Paper Space ok? When you have multiple paper space tabs in your file and your dimensions do not carry over from sheet to sheet.
When you dimension in Model Space make sure to use annotated dimensions. This AutoCAD feature will display your text and arrows at a defined paper height regardless of the scale of the viewport.
When you dimension in Paper Space make sure the AutoCAD system variable DIMASSOC is set to a value of (2) two. Also make sure that your dimension styles do not scale the length of the measurement. Keep this value at (1) one. That is the DIMLFAC variable. If you are going to create Dimensions styles for specific scales then you have to set a value for DIMFLAC and set DIMASSOC to either (o) zero or (1) one. But why create more dim styles to have to manage? But why create a possible dimensioning error because the wrong dim scale was used? If these settings are not correct then dimensioning in paper space is a chore.
A long time argument against dimensioning in paper space (and it’s a good one) has been that if the linework moves you have to move the paper space dimension. Well, if you set (as I recommended) DIMASSOC to (2) two then any dimension that is associated to that linework will update automatically. Besides, if your model space linework changes then you will still have to update your model space dimensions. But then again DIMASOC set to (2) two will update that as well. (This setting works with leaders too.)
Now for my personal preference coming from an AEC design background. Annotate in paper space. If it is a street name, lake designation, or some major attribute that needs to be displayed everywhere then annotate that in model space but keep it limited. Everything else goes in Paper Space.
What do you do and why?
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The only time dimension should be in paper space is when the associated line work is also in paper space, details for example.
ReplyDeleteIf you wish to keep your model mostly free of annotation, xref it into another drawing and annotate there, then xref that into your sheet.
But the problem in dimensioning in paper space is that when model drawing were updated or moved the dimensions gives inaccurate lengths. for example, if i have a drawing which have a 3000 in dim length, after some modifications, dimensions becomes very inaccurate anymore giving me a different sizes. I noticed that one specially working on big files. Have a check
DeleteThat's why i recommend to dimensions should be on model space only, and any annotations like leaders, text, tables and tblocks should be in paperspace.
Thanks.
We create a separate drawing for dimensions in model space. This drawing is an xref in the appropriate sheet and no others. Keeps the base file clean and you can have multiple people working on the project with one assigned to verify that all dimensions have been updated.
ReplyDeleteThanks for the comment MrJackson. I am curious. Why never dimension in paper space? What are the reasons?
ReplyDeleteI think it makes for a cleaner drawing, easier to move things around without having to worry about something getting missed or jumping around. You also don't need to switch between paper space and model space often when working.
ReplyDeleteIf you draw in 3D then dimensioning in paper space might be your only option.
ReplyDeleteIf you only ever have one view on each sheet then I could see how you could dimension in paper space, but it always seems a little unreliable to me. Even with dimassoc set to 2 you have to do a lot of toggling back and forth to check that there are no mistakes.
We do a lot of broken views, with the item drawn at full size in model space, but only the joints and junctions shown in viewports. In this case dimensioning in model space is the only option.
My preference is dimensioning in paper space - using Xref's if it is a shared base file.
Why would you ever want dimension in paper space? If there are dimensions that you do not wish to show in every layout, put them in a special layer and use VP freeze to hide them or put them in an xref.
ReplyDeleteGreat question @Soylent and great solution. I typically dimension in Paper Space because we typically have multiple tabs in a a file that overlap. I have no desire to make multiple layers for display controls. To me it adds more work and more file management that can cause issues in the future. If I am the only one that ever works on the file then that issue goes away. I know what was done. Typically where I work we often have multiple people working in the same project and drawings so they need to be streamlined and mostly independent meaning that If i change something in a drawing only that drawing is affected. Adding new layers to accommodate new dimensions in a new tab (as an example) can cause issues. There are many good reasons to dimension in model space; if the scale of the viewport is likely to change, if the dimensions need to show up in multiple viewports/tabs, if the final setup of the viewport is not set. Moving a viewport, rescaling a viewport, is much easier to do when the dimensions are in model space. In my case that rarely happens. Changing the scale of a viewport with dimensions in paper space is an issue. That rarely happens to us as we set the views before we start to dimensions them.
ReplyDelete