Virtual Display

A virtual display is similar to a “2D Display/Projector” in many ways, except it is not associated with a physical display connected through a display computer. Instead, whatever is displayed on it is made available for reuse inside WATCHOUT itself.

Virtual displays1
A virtual display named “Texture” has been added to the Stage window.

When you add a virtual display you also get a new entry in the Media window with the same name.

Virtual displays2
The same virtual display also appears in the Media window.

You can use this virtual display media anywhere you use other types of video or images in WATCHOUT, and you can apply all the same transformations and effects to it. This has two main applications:

  • Manage LED wall modules, or other kinds of display devices with odd pixel dimensions, often connecting through some kind of processor, which manages several modules by mapping them into a common pixel space.
  • Create textures for 3D objects using the full power of WATCHOUT, including multiple image and video layers, tween tracks, dynamic content (such as live video), etc.

Managing LED wall modules

LED walls are typically made up of a large number of square “LED tiles”. Each tile has a resolution based on its physical size and LED density, for instance 144 by 144 pixels. Due to this unusual resolution, and the common need for using a large numbers of tiles, the tiles aren’t connected directly to a display computer, as is the case with most other displays. Instead they’re connected through an “LED wall processor”. This processor accepts standard video formats, such as 1920x1080. The LED tiles it manages are then mapped into this pixel space by configuring the system and the processor accordingly. This mapping can be straightforward by placing all tiles in rows and columns to recreate most of the 1920x1080 display.

Virtual displays3
A large number of 144x144 pixel LED wall tiles mapped into a 1920x1080 pixel space.

More often, the pixel budget is used in more creative ways, for example as a narrow and very long strip.

Virtual displays4
26 modules making up a narrow strip of 3744 by 144 pixels.

When producing the presentation in WATCHOUT, you generally want to have the displays in the Stage window arranged in a way that resembles their physical arrangement, and not the arrangement fed to the processor. In the example with the long, narrow strip above, you want to be able to have text and images slide across that entire 3744 pixel wide display area.

While you can’t make a 3744 by 144 pixels regular “2D Display/Projector” in WATCHOUT (because no computer can output such an odd resolution), you can make a virtual display of that size. Images appearing on this virtual display can then be mapped onto a real display, as two copies of that single, long virtual display, like this:

Virtual displays5
A long LED strip mapped twice onto a 1920x1080 pixel space.

The reason you need to map the long strip onto a real display is that the processor driving the LED will generally only accept standard video or computer resolutions, such as 1920x1080 in the example above. The processor will then do the reverse mapping, putting all the pixels back where they belong along the long, narrow strip of LED tiles.

IMPORTANT: When using virtual displays, always create as few virtual displays as possible. Do not create one virtual display per LED tile. In the example above, you could make either a single, long virtual display covering the entire 3744 pixels, or you could make two virtual displays side by side, each 1872 pixels wide (as shown by the colors above). Using a large number of virtual displays may degrade the performance of your system.

Here’s another example of an arch-shaped structure built with the same kind of LED modules:

Virtual displays6
An arch-like structure built from 32 144-pixel LED modules.

Again when representing this in WATCHOUT, use as few virtual displays as possible, for example one for the blue strip along the top and one for each side. Then assemble the resulting three media objects onto a real “2D Display/Projector” using cues on a timeline in any appropriate manner to feed the pixels to the LED wall processor. This will then map them back onto the arch structure.

HINT: Use a set of cues on a paused auxiliary timeline to map the virtual display media elements onto the real display, leaving your main timeline clean and uncluttered for your production work.

The video on producing for LED walls gives a more visual description of how this is done.

Creating Dynamic Textures

While you can use a simple image or video to texture a 3D model, it gives you very little flexibility in how the content is played and positioned. For instance, you can’t do any of the following using that simple method:

  • Position an image anywhere on the 3D model (the entire image will be mapped into the UV space of the 3D model, with no control over its placement).
  • Compose multiple images, video and other content using several layers to build the texture (only a single image element can be used).
  • Change the content mapped onto the 3D model over time (only a single image element is used for the entire duration of the 3D model’s cue).
  • Loop a piece of video used to texture the model (since the video doesn’t have a cue of its own, there’s no place to turn on looping).

All of these restrictions, and more, can be alleviated by first mapping whatever content you want onto a virtual display, using the full capabilities of WATCHOUT, and then using the virtual display’s media item as the texture for your 3D model.

To use this method, follow the steps below:

  • Create a virtual display of the desired resolution.
  • Render content onto that virtual display using multiple layers and cues, as you normally use WATCHOUT.
  • Locate the media item corresponding to the virtual display in the Media window.
  • Add the 3D model to your timeline, positioning it as desired.
  • Make sure the 3D model’s cue is selected.
  • Drag the virtual display’s media item from the Media window onto the selected 3D model in the stage window.

Usually, the virtual display will be square, with a resolution that’s a power of 2, such as 2048 by 2048 pixels. That’s not required by WATCHOUT, but is customary for 3D texturing. Discuss this with your 3D artist. If desired, create the virtual display on a separate tier to keep it out of sight for other displays and projectors (see “Stage Tiers”). The resolution to use for the virtual display should be based on the following factors:

  • The resolution of the content you’re going to place onto it. There’s no point in using a higher resolution than that of the content that will be rendered onto it.
  • The physical size of the object on which you are projecting. If it is a small object, or only going to be viewed from afar, you won’t be able to see any very high resolution content anyway.
  • The resolution of the projector used for the projection. Since you often only use a part of the projector’s raster image to cover the 3D model, the resulting resolution is often well below that of the projector.

Check out this video for an overview of how this technique can be done. The video also discusses how to use multiple virtual displays to texture different areas of a 3D model (see “Using Multiple Textures”).

Preview Quality

The quality of the virtual display media in the production software is lowered to increase performance. There is an option to view it in full quality by selecting the “High Quality” media preview setting in the virtual display dialog. This is useful, for example, when using the virtual display as a texture on a 3D model.

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