Your questions answered, Dimensioning in model or paper space?

This weeks question comes from David.

David asked:

When dimensioning a drawing what would you say is the industry standard method for setting out?
A – Dimension in model space using different size text for each scale as viewed in a view port.
B – Dimension in paper space using one text size with associative dims turned on.
Or is there another method?

Great question – I’m afraid it does depend on what industry you’re in!

Dimensioning 3D models

Dimensioning in paper space can be unreliable, because the dimensions don’t always update with the model space geometry. However it can be made to work in the right circumstances…

Firstly, If you use 3D with traditional floating paper-space viewports, dimensioning in paper space is the only reliable way. Dimensioning in model space is unreliable because it’s way to easy to snap a dimension to the wrong point.

AutoCAD 2013 onwards has a new way of creating 3D views that is much closer to Inventor. There are no floating viewports required – all the views are created as a special kind of block in Paper space. You can dimension in paper space with far more confidence than before.

Now 2D…

Dimensioning 2D models

If you are an Architect, dimensioning in paper space might work out just peachy. Characteristically, architectural drawings involve many Xref’s compiled in model space, with just one floating view port per layout.

The size and position of the view port isn’t likely to change over the duration of the job, so you can dimension in paper space with confidence that your dimension won’t become un-associated by moving the view port around. Because there is only one view port per layout, you only have one place to check and see that you’re dims are OK.

If you are an Engineer, it’s likely that your drawings will contain a great many more orthographic views. In this case, you may well have multiple floating view ports on a layout. In the Joinery industry we often create ‘Broken’ views with the item drawn full size in model space, but only the interesting bits laid up on a sheet.

In this case, checking that the dimensions have updated correctly in paper space every time you edit something in model space is just a Right Royal P.I.T.A. and creating dimensions that cross paper space between viewports simply isn’t possible.

Most people I’ve worked with prefer to dimension in model space, with multiple dimension styles and layers for each view port scale. It’s a bit fiddly to set up, but as you edit geometry you are editing the dimensions and annotations at the same time, so you know they’ve updated correctly.

Dimensioning in Model or Paper space?

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and finally…

There is another way! In order to get around this dilemma, Autodesk created ‘Annotative‘ dimensions. This is a special kind of annotation that contains many different sizes of text which automatically turn themselves on and off depending on the annotation scale or view port scale.

This is also fiddly to set up – and your whole office need to understand the technique (as well as your subcontractors and maybe even your clients!) – probably because of this, I haven’t heard of anybody successfully using this technique (that doesn’t mean that someone – somewhere – isn’t proving me wrong!).

Phew – that was a great question David, I hope that you found my answer enlightening, if not exactly decisive ;)

What’s your view?

Do you prefer to dimension in model or paper space? Why?


17 Responses to “Your questions answered, Dimensioning in model or paper space?

  • The viewport and annotation scales are synchronized when the annotation scaling controls are used. For example, when i change the viewport scale, the annotation scale updates to match the new viewport scale. However, as i zoom in or out of a viewport with my mouse wheel or by using the Zoom commands, the viewport scale updates while the annotation scale will remain unchanged.
    Whenever an annotation object is added to a drawing, the current annotation scale is added to the object as a participatory scale. AutoCAD Architecture objects identified as annotative will scale to match the current annotation scale.
    How can i resolve it ,I dont want that when i change the viewport scale, the annotation scale updates to match the new viewport scale.
    Please advice how could i resolve it.

  • elind21
    9 years ago

    I wish dimensioning in AutoCAD worked like it does in Inventor. The system is so much better. I also wish that drawing would follow some of the same coding rules as inventor sketching. Everything is right there and it is so much easier to use (it is sometimes finnicky, but AutoCAD is always)

  • I will always believe and train individuals to use the Model Space.I understand that Print Space dimensioning can be done under certain circumstances, I think there are too many risks of making mistakes especially if you’re new to the program.

  • I am a fan of layout/paper space. But I never really like annotating in paper space. I tried to fully work with annotation in paper space, and it’s not convenient.
    But it really depends on your drawings. Some drawings probably better with paper space dimensioning, but I believe model space would fit for all drawings.

  • As with everything, it depends.

    I work in the entertainment industry. We heavily mix architectural, mechanical, engineering, and schematic styles/disciplines, so we see every dimensioning method under the sun. I personally use annotative because it lets me use six standard dimension styles to control the formatting of the dimensions (units, precision, visual representation, etc) instead of having a style for each scale and manipulating the other bits manually (or having 40 different dim styles, one for every case). I’ve rolled the annotative styles into our standard templates, and everyone is doing well with them after a little initial training.

    The one thing we don’t do anymore is use 1 dimension scale, and scale the actual drawings in modelspace; those were dark days, and I hope to never see the like again.

    When drafting in 2D (schematic, structural, arch, simple mechanics) I’ll dimension in modelspace. For me, speeds up layout, makes the drawing more flexible, and is generally quicker to revise.

    When annotating 3D models, I’ll dimension in paperspace using the baseview objects and they’ve been great. Dimensioning to them is much easier than the paperspace w/ viewports method, and they don’t randomly jump around when you edit or move parts in the model (they look really good too). I still get to use my six annotative styles though, since they come out just fine in paperspace too. Though at times you have to cheat when you want to dimension from the 3D model to a centerline or phantom line in paperspace.

    • Sounds great. Matt, Have you tried using Inventor for your 3D? Baseviews are a technology inherited form Inventor’s layout tools…

      • Yeah… some of our people use Inventor, I use it for a little bit of mechanical analysis and specialty stuff. Its a touchy subject in our office, as both camps have very strong opinions on the matter. I personally don’t think its a good fit for 90% of the projects we do; our lead times are often incredibly short – often times we don’t have time to finish the designs before the shop starts building them. There’s also the training investment issue, we (and our other locations, clients, and competitors) are heavily invested in Autocad. I have a laundry list of other reasons, but I’ll admit the biggest is that I’m biased… I love the immediacy of manipulating objects in direct modeling; its an incredibly powerful 3D sketchpad. I’ll work out ideas in a very short amount of time without knowing the solution before-hand, and I can’t seem to match that feeling of immediacy with parametric modelers.

        • Funnily enough I started out 3D modelling in AutoCAD.

          My two frustrations were that simple changes in AutoCAD (like adjusting something to fit a site survey) were such a pain in the Arse, and that I couldn’t get a decent drawing off an AutoCAD model.

          I still like draughting in AutoCAD (I still like sketching by hand!) But I prefer Inventor for anything complex.

          I guess you get use to the tools you use in time :)

          Have you tried Fusion 360? That product looks like the best of both worlds…

          • I haven’t taken the time. I used Fusion when it was included with Inventor and as a tech preview, but the inability to save feature information between sessions was a no-go. I’ll have to give it another try; a hybrid feature and direct modeler would be great.

      • elind21
        9 years ago

        I agree, Inventor is totally superior.

  • Brian
    11 years ago

    The first company I worked for, which did $100M civil engineering projects, had dimensions put in paper space. I thought this was the “right” way to do it. Then I moved on to an even bigger company, and found out they put their dims in model space.

    For the past 7 years I’ve worked as a CAD Consultant to small AEC firms in NYC. It’s a rarity to find someone who dimensions in paper space.

    Lastly, the PANYNJ has an awesome CAD Standard, and they dimension in model space.

    Personally… After having been exposed to both ways of dimensioning, I prefer to dimension in model space using a different dimension and text style for each scale as viewed in a viewport.

  • For 20 years I have ALWAYS dimensioned in MS, either by having one style which scales using DIMSCALE or with multiple styles for each scale (it depended on the CAD standards)
    Now I have made the switch to annotative text and dims, in MS, and it’s so EASY now! Yes, there’s a slight learning curve but it’s worth it.
    But why MS? Because PS dims are just a PITA in general.