Understanding paper space/model space

- AutoCAD allows us to draw our geometry in real scale, or one-to-one. This means we can draw a house in real dimensions. But eventually we still need to print black lines on white paper. To scale our final prints, AutoCAD uses layouts and concepts known as paper space and model space. These are somewhat abstract concepts, so don't feel bad if it takes a little practice and use to become comfortable with them. Obviously, we cannot print a full house plan at one-to-one scale on a piece of paper, so it must be scaled down.

Rather than scaling down our geometry and losing the convenience of drawing in real space, we'll use layouts. Model space, shown here, is where we create our object geometry drawn in real dimensions. Here, if I use the distance tool, we can see that this house is drawn at one-to-one scale, 46-foot wide by 41-foot deep. This means that all the lines and all the components are drawn in real dimensions. Here we find layouts. Each layout represents a single piece of paper, and is also drawn to real scale.

So here I have a 36-by-24 rectangle to represent my 36-by-24 piece of paper. Now to show the geometry I create in a model space, I'm gonna cut a hole in this piece of paper called a view port. Think of a view port as a hole with a piece of glass in the paper. The glass allows us to look through the paper into model space below. But the glass can be used to magnify the model to scale so it fits on the page. In pencil drafting we used a standard set of scales, which we'll use here as well.

Here we can use mechanical scales, like 1-to-2 or 1-to-10, as well as architectural scales, like one-eighth inch equals a foot, or one-quarter inch equals a foot. Now before the model space and paper space really took hold, AutoCAD drafters used to scale their dimensions and page layouts to the scale they wanted to print the page at. Like scaling everything by a factor of 48 for a quarter-inch equals one foot scale. The problem came when you had multiple sheets at different scales, or wanted to zoom in to show details at a larger scale.

Dimensions and text would be scaled, too. This meant occasionally dimensions and text would be in the wrong scale and print at different sizes on the same page. Today there are still two schools of thought on using layouts. I see some firms adhere to this older method. Using paper space, drafters would create their pages, as I mentioned, but use a single view port to show everything in their drawing. The other school of thought, of which I find slightly more useful and more closely tied to how the concepts of paper space and model space were originally intended, is to draw your geometry in model space, as I have here, and then place all of your dimensions, all of your annotations, in paper space.

All the annotations, including dimensions, notes, call outs and any other information that essentially does not exist on the final produced product being drafted. In this case, when I actually build this house I wouldn't have the word Living Room stenciled on the floor. If it doesn't go in the final house, it doesn't go in model space. Using this method, you can create just one dimension style and one text style, and these are created at the size you want to see them on the printed page. Text created at a quarter of an inch will be plotted at a quarter of an inch when the page is printed.

This allows for consistency, as well as not needing a dozen dimension styles for every scale. Again, these concepts are slightly abstract and require a little planning and a basic understand of drafting principles, but with the tools provided in AutoCAD for MAC, they should help and allow you to create and use your geometry to your full advantage.