Floating windows

written by Eric Deren, February 24, 2008

Objects appearing in negative-z space (between the screen and the viewer) can sometimes be problematic if they intersect the edge of the screen.  This is because the edge of the screen, which usually acts like a window, is now creating a retinal rivalry, allowing you to see part of the object with one eye, floating over the area beyond the frame.

(insert image with window violation here)

This is called a window violation and it is uncomfortable for the audience in most viewing situations.  Careful scene composition is the primary defense against window violations.  However, there are situations where, for artistic reasons, objects will need to cross the edge of the screen while in negative-z space.  This is where a “floating window” is used.

(insert image with floating window correction here)

The theory is to move the perceived edge of the screen into negative-z space by enough to allow objects in negative-z space to pass behind the edge of the screen.  In practice, it is as simple as matting the left edge of the left eye, or the right edge of the right eye, by the same number of pixels as the width of the parallax difference of the negative-z object in question.

This matte should be the same color as the edge of the screen, which in most theatrical situations will be black. However, if the content is being shown on a website with a different colored background, that background should be replicated in the matte. I have padded all of the images on this page with black to allow the floating windows to be effective. I could have also acheived this effect by coloring my entire background black. For obvious reasons, a textured background would be counter-effective.

Floating windows, if they are done correctly, will not be noticed by the average viewer.

Floating window notes:

  • Feathered floating window edges

      Some people believe that this floating window edge should be feathered or "blurred". This will work, as long as the blur is matched on the floating matte and the edge of the screen. However, feathering is not necessary. It works just fine as a hard line, because viewers are used to seeing the edge of the screen as a hard line.

  • Animated floating windows

      Floating windows can even be animated (albeit slowly), pushing out to accommodate a negative-z object, and then pulling back to allow for the maximum screen to be used again.  It should be noted that changing directions without a pause will probably be noticeable.  The acceptable speed of floating window animation and the amount of pause time needed to hide a change in direction is dependent on subject material and the existing motion onscreen… if there is more going on visually, the audience is less likely to notice the modifications of the floating window.

  • Can floating windows be used on the top and bottom of the screen?

      Yes, but they are not common. To create a floating window on the top and bottom of the screen, one would be required to disrupt the top or bottom edge of the screen with something your eye can resolve to create depth. In normal viewing situations, the horizontal edges do not return depth information and our brain just assumes that they connect to the left and right edges of the screen. To create depth information, one would have to add detail of some sort, either with a texture or by using a shaped matte.

    (include picture of floating windows on all sides)

    [an error occurred while processing this directive] No pathinfo