Background Masking

Most of my blog entries are simplistic in nature. This is on purpose. My validation is that somewhere, someone is a brand new Civil 3D user. so my posts are aimed at them (as well as the Introducing C3D book). So this is a continuation on that vein. The rest of you more seasoned veterans can follow along too.

Have you ever wondered why or how the background mask sets its invisibility? Check it out after the jump.

The background mask is nothing more than smoke and mirrors on Autodesk’s part. Here I have a surface with some contour labels applied. Notice how the text appears to be floating above the line.


The mask color is actually set to the color of your background. Don’t know how to change your model space background from the Civil 3D 2010 off-white default, to black? Simply:

  1. Go to Options. This can be accomplished many ways, but the easiest one for me is to right-click on the commandline and select Options…
  2. Click on the Display tab and on the left-hand side, pick the Colors… button.
  3. In the Drawing Window Colors dialog box, make sure that Context: is set to 2D Model Space and Interface element: is set to Uniform background.
  4. Now look at the right-hand side under color: and change the color to your liking. 99.99% of the people that I have run into prefer the old (pre-2010) color of black.
  5. Click the Apply & Close button at the bottom. This dismisses the Drawing Windows Colors dialog box.
  6. Click OK to save your changes.

So back to background masking… to prove my point, I will change my background color to something drastically different. And if I were to do some more contour labeling, the background would inherit this new color.


In my example, you can see that the background color is still set to black even when we changed the physical background color.

Again, we’re keeping it simple here folks. But the inquisitive person in me wants to know how paper space works with this background masking and why, when one explodes a drawing that contains Civil 3D masking objects (such as contour labels) does the mask show up in paperspace as a black hatch pattern. But that is for others to let me know – which I’m sure they will.


  1. Hey Rick,
    Sort of along this topic, I’d like to point out the new component for 2010 on the contour labeling. Maybe you want to expound upon the “Contour Line Only” masking. This seems to be a good alternative for those that are having problems with the plotting using the background mask or having to create a “wipeout” block in their contour label style.
    I really haven’t looked into the internal components of how this is done, but it doesn’t seem to be using a colored hatch or wipeout object when exploding them.

  2. J. Stevens says:

    When you explode or save back to a previous version of cad those black hatches become an issue because you can’t see the text under it when you plot. We have run into this a few times when sending drawings out of the office. We have since set all of our styles up to use wipeouts instead. The background masks would be much nicer to use if it weren’t for this issue and also the fact that our OCE plotter ignores them.

    • Rick Graham says:

      We also have an Oce Plotter and run into that same problem regularly. Luckily, if you plot from paperspace, you may be able to see those voids. What we do is select one, right-click Select similar and then press the DEL key, All black voids are gone. Or if they are persnickety, we have to use the filter and select only the hatch with color 250 and then erase. of course if you’ve changed your background to something else (like I did in the example above), then you’d have to erase that color too.