by Montgomery Martin

Prior to this tutorial, you may wish to review Tutorial X: Video Output to familiarize yourself with the basics of working with a single video output source.

Working with multiple displays opens up powerful design options. Using multiple instruments empowers you to create massive display walls, intricate overlapping designs, and three-dimensional interactive spaces filled with dynamic video or graphical effects.

Isadora supports up to six video output channels, called Stages. In this tutorial, you will learn how to configure Isadora to facilitate video output to up to six displays.

What is a Display?

  • Typically, a digital video projector. Since Isadora uses the term “projector” quite specifically to refer to the Projector actor, it’s not uncommon for Isadora users to call these instruments “beamers” for the sake of clarity. “Beamers” are extremely diverse, and range from small, hand-held units to massive cinema-grade machines.

  • A television set

  • A discrete computer monitor.

  • The built-in monitor on a laptop computer

There is no requirement to use identical units or displays with Isadora, as the application automatically detects the resolution of each display. You could work with two different projectors plus a television set, for example. However, users interested in using Isadora’s multiple display features, such as edge blending and projection mapping may wish to consider the visual consistency offered by using identical units.

Part 1: Choosing the Right Hardware

You may already be familiar with connecting a single video output to your computer, so in this section we will discuss how working with two or more video outputs simultaneously may require additional hardware considerations.

Just as with a single video output, your computer must have a video output device of some kind to connect to a display. When securely connected to your computer, Isadora will “see” this display automatically. The most ubiquitous types of video output connections today are VGA, HDMI, and DVI.

As laptops continue to shrink in size, fewer machines are manufactured with physical VGA or DVI ports. Instead, many computers include a MiniDisplayPort or Thunderbolt Port. While the ports are identical and compatible for video output purposes, Thunderbolt includes additional functionality. By using a MiniDisplayPort to VGA, HDMI, or DVI adapter, we can cover the MiniDisplay Port or Thunderbolt port to whichever connection we require.

Most laptops only support a single video output without additional hardware. However, a notable exception to this is the Apple 15” Macbook Pro with Retina Display, which can support up to three video outputs on its own. Apple’s powerful Mac Pro desktop units are also equipped with six Thunderbolt ports, although Apple’s specifications note that the machine can only support output to a maximum of three displays at a time.


A Matrox TripleHead2Go unit connected to three computer monitors.

A Matrox TripleHead2Go unit connected to three computer monitors.

Many users ask if there is some way to “split” the video outputs to operate more then one display on a laptop or machine with only one output. We recommend such users consider the Matrox DualHead2Go or TripleHead2Go, which facilitate additional displays. Later in this tutorial, we will discuss how Isadora includes additional options that make working with a DualHead or TripleHead easy.

It is technically possible to combine a TripleHead with the additional outputs on a 15” Retina Mac to output four or more displays. However, depending on your design, this may tax the limitations of your machine. We recommend users operating more then three displays from a single computer consider a powerful desktop solution instead of a laptop.

Desktop PCs can be built with a wide range of dedicated graphics cards, which may support a variable number of outputs. The number of physical ports on a graphics card may not be an indicator for how many displays it can actually support, however. Careful research is required when purchasing a graphics card to ensure it can support the number of displays you require!

Part 2: System Set-up (Mac OS X)

Note — If you are using a Matrox TripleHead or DualHead, follow the instructions from Matrox to configure the device and connect your displays before starting these steps.

  1. Connect all your display units securely to your computer, and power each unit on. As the displays are connected, it’s normal for the screen to flash once or twice. Once all your units are connected you may notice the resolution of your display has changed, or that all of your open windows have moved from your main display to one of the other displays. Navigate as best you can for now: we will be setting everything up properly in just a moment.

  2. Tip — As a best practice, it is wise to test your physical connections and configure your system before mounting your displays, especially if you need to hang your beamers in a lighting grid. Make sure you have a clear, flat, simple surface to point your beamers at during this process! Furthermore, if you are using display extension cables to cover a very long cable run, you should thoroughly test the cables first. Once you know that everything is working and set up properly, you can take it all apart, hang and focus your beamers, and run the cables.

  3. On Mac OS X, launch System Preferences.

  4. Choose “Displays” from the system preferences menu, and open the “Arrangement” tab. You may see a screen that looks something like this one:

  5. Disable the “Mirror Displays” option, if it is checked. Your displays may flash again. If the “Mirror Displays” option is already unchecked, leave it unchecked.

    Mirrored Displays

  6. After disabling the “Mirror Displays” option, or after connecting your displays if the option was already unchecked on your system, the System Preferences tab may have moved to another display (as well as any other items you had open). We will correct this in a moment. Regardless, your Display Preferences window should now look something like this: 

  7. Note — In the example image above, my computer is connected to two projectors and an LED Cinema Display for a total of four displays. Depending on how many displays you have connected, you may see something slightly different. If this panel shows fewer displays than what you connected, check your hardware.
    Note — If you are using a MatroxTripleHead or DualHead, you will see only your Main Display and one elongated rectangle instead, like this: OS X Display Arrangement with Matrox Triple HeadEach of the blue rectangles represents one of the connected displays. You can easily identify which display is which with a single click, since a red outline appears along the outer edges of the actual display when you click it.

  8. Set the main display. The white bar that runs across one of the displays represents the OS X menu bar. Isadora will recognize the display with the menu bar as the “Main Display” in your setup. Our Main Display will be the screen we will use to edit and control Isadora, and will not be used as a video output stage. Typically, this is the built-in display on your laptop computer or the main monitor on your desktop computer.

  9. Click and drag the menu bar from whatever display it is currently on to whichever display you wish to use as your Main Display now. While you perform this action, OS X will outline the display the mouse pointer hovers over in red to help you identify the correct one.

  10. You’ve now set up your multiple displays on OS X, and it’s time to configure Isadora’s stages. You should now see a desktop image on each screen. You should be able to drag the mouse pointer across your displays. At this time, you may want to see the desktop image to a flat black (or white, depending on your design.) This way, if your computer freezes or Isadora unexpectedly crashes, your audience simply sees a blackout instead of an image of the Yosemite or El Capitan mountain

Optional: Hiding the Menu Bar on additional displays in OS X

In newer versions of OS X, Apple may show the Dock and Menu bar on each display. Unfortunately, this causes the menu bar to overlay Isadora’s stage output, and is quite unsightly. However, it is easily corrected:

  1. Return to the main System Preferences panel.

  2. Choose “Mission Control”.

  3. Uncheck the option “Displays have separate Spaces”. Note that you will need to log out or restart your computer before this option is applied. Do so now.

Part 3: Setting up Isadora

  1. Launch Isadora and start a new file.

  2. From the menu bar, choose Isadora > Preferences… (Mac OS) or Edit > Preferences… (Windows) to open the Isadora Preferences.

  3. Click the "Stage” tab. You should see this panel:

  4. As a reminder, Isadora supports output to up to six displays, which we will call Stages. We will now assign each display to a stage.

  5. Set the stage for “Stage 1” by clicking the drop down menu labelled “Place On”. A list of the displays connected to your machine appears, showing the number and resolution of each display (see below)
    Screen Shot 2016-01-06 at 12.48.13 PM
    From this list, choose the display you wish to assign to Stage 1. Remember, you normally don’t want to assign your Main Display to a stage!

  6. Repeat this process for each stage until you have assigned each display to a stage. You don’t have to assign a display to each stage.

  7. Tip — Write down your stage to display assignments! Think of this exactly like the instrument, dimmer, and channel assignments in a lighting system.

  8. Click OK to finalize your display assignments and return to the scene editor.

For users working with a Matrox TripleHead or DualHead only:

You’ll notice that you don’t have many options in Step 5: your computer thinks the three beamers connected to the Matrox device are one long display. Isadora includes a special feature here just for users like you which helps “split” this display back into its discrete parts. Beside the “Place On” drop-down menu, we have another drop down menu that is set to “Full” by default. Within this drop down, you can configure Isadora to only use one-half or one third of the display as a stage:

The different stage options for a Matrox Triplehead of Dualhead

When using a Matrox DualHead, set Stage 1 to the Left Half, and Stage 2 to the Right Half. Make sure the drop down option for “Place On” is set to the same display for both stages.

When using a Matrox TripleHead, set Stage 1 to the Left Third, Stage 2 to the Mid. Third, and Stage 3 to the Right Third. Make sure the drop down option for “Place On” is set to the same display for all three stages.

This feature is designed for the unique way the Matrox products work. Since your computer recognizes a Matrox triple head not as three distinct displays, but as one “extra-long” display, this feature allows you to treat the displays as discrete entities within Isadora. It is essential that you “divide” your display to properly use the TripleHead or DualHead!

Part 4: using Multiple Displays in the Scene Editor

Now that you have configured your stages, lets try making a simple patch to test the configuration and learn how to use multiple stages in the Scene Editor.

  1. In the same Isadora file you used to configure your Isadora Preferences.

  2. Import three different image files from your computer into your Media Bin.

  3. Drag one Picture Player and One Projector actor for each Stage you have created from the Toolbox into the Scene Editor.

  4. Link each Picture Player to the Video input on a different Projector.

  5. Choose one of the Projector actors, and set the “Stage” output to “2”.

  6. Choose a different Projector actor, and set the “Stage” output to “3”.

  7. Leave the “Stage” output on the last Projector actor as “1”

  8. Choose Output > Show Stages. You should see a different image appear on each beamer’s output!

Many other actors use the Stage output to determine the destination stage for the video stream received by that actor. Each actor works on the same premise: simply change the number on the “stage” input property to the corresponding stage you wish to send the video output.