3.1Model space vs paper space: viewports (windows) & scales
This is THE concept that unlocks professional layout: the distinction between model space (Model) and paper space (Layout). You always draw in model space at 1:1 scale (a 5 m wall measures 5000 mm). You lay out in paper space, on a virtual « sheet » at paper size (A3, A1…).
The bridge between the two is the paper space viewport: a « skylight » cut into the sheet that displays the model space drawing, at a precise scale (1:50, 1:100…). You can create several viewports, at different scales, on the same sheet (a general plan + an enlarged detail). Understanding this mechanism is finally knowing how to print right — the foundation of all of level 3.
Section vocabulary
- Model space (Model)
- Drawing space at real 1:1 scale. All the geometry is built there.
- Paper space (Layout)
- Virtual sheet at paper size for layout and printing.
- Paper space viewport
- « Skylight » in the sheet displaying model space at a given scale.
- Viewport scale
- Display ratio of the drawing in the viewport (1:50, 1:100…), lockable to avoid misadjustments.
- Viewport lock
- Freezes a viewport's scale so an accidental zoom doesn't change it.
What does a paper space viewport display?
In practice — Laying out with viewports
- Switch to a Layout tab; it represents a sheet at paper size.
- Create a paper space viewport (MVIEW): it displays your model space drawing.
- Double-click inside the viewport to enter it, set the precise scale (e.g. 1:100) then LOCK the viewport.
- Add a second viewport at another scale (a detail at 1:20) on the same sheet.
Key points to remember
- You draw in model space at 1:1 scale.
- You lay out in paper space (sheet at paper size).
- The viewport displays model space at a precise scale.
- Locking viewport scales avoids accidental misadjustments.
Frequently asked questions
Why not simply draw and print everything in model space?
Because model space is at real scale: to print a 20 m building plan on an A3 sheet, it must be reduced to a scale (1:100). Paper space handles exactly that, cleanly, and allows several views/scales on the same sheet with a title block. Printing directly from model space is possible for a quick sketch, but does not allow professional multi-scale layouts.
How do I set the exact scale of a viewport?
Enter the viewport (double-click inside), then assign it a standard scale via the scale list (status bar) or the Properties palette (« Standard scale »). Once the scale is correct, lock the viewport (padlock in the status bar): that way, zooming in to navigate will no longer change the scale. It's an essential step for a reliable sheet.