How to Set Up Stereoscopic (3D) Output
How to Set Up Stereoscopic (3D) Output
Configure Backstage to output stereoscopic 3D content through one or more projectors. This covers the entire workflow: preparing stereo assets, creating a Stereo Channel Container, configuring projectors for left/right eye rendering, selecting a stereo output mode, and routing the signal.
Before you start
- A scene with at least one Surface and one or more Projectors
- At least one GPU output detected at startup
- Stereo 3D content — either two separate files (left/right eye) or a single top-bottom or side-by-side encoded file
- For Active 3D Stereo mode: a GPU and display connection that supports quad-buffered stereo (e.g. NVIDIA Quadro/RTX with 3-pin sync)
- For WhiteLine mode: a compatible 3D sync distributor connected to your projector(s)
Steps
1. Prepare stereo content
You have two options for delivering stereo content to Backstage:
Option A — Stereo Channel Container (recommended for separate files): Import your left-eye and right-eye media as separate Assets. Then create a Stereo Channel Container to combine them.
Option B — Single top-bottom encoded file: Import a single video or image sequence where the top half is the left eye and the bottom half is the right eye. Select the asset, then enable Top-Bottom Stereo Asset in the Inspector under the asset's visual properties.
2. Create a Stereo Channel Container
If you chose Option A above:
-
Open the Assets window.
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In the Stereo Container section, click Create Stereo Container.
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Select the new Stereo Channel Container. In the Inspector, set Channels to Stereo 2 (for standard left/right stereo).
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Assign your left-eye asset to Channel 1 and your right-eye asset to Channel 2.
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Optionally, rename the container in the Name field for clarity.
The Stereo 4 option assigns four separate assets to four channels. This is used for specialized multi-view setups, not standard left/right stereo.
3. Configure projectors for stereo
Each projector must be told which stereo channel to render.
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Select the first projector in Scene Objects.
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In the Inspector under Projector Properties, enable Project Stereo Content.
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Set Use Stereo Channel to Channel 1 (left eye).
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Select the second projector and repeat: enable Project Stereo Content, then set Use Stereo Channel to Channel 2 (right eye).
For a single-projector Active 3D setup (e.g. frame-sequential with shutter glasses), you still enable Project Stereo Content on the projector. The stereo output mode on the Output determines how both eyes are packed into the signal.
4. Assign stereo content to the surface
Create a Sequence with a Video Channel targeting your projection Surface. Place the Stereo Channel Container (or the top-bottom stereo asset) as an Event on that Channel. Backstage automatically routes the correct eye to each projector based on the Use Stereo Channel setting.
5. Enable stereo on the output
Open the Outputs window and select the GPU output driving your stereo projector(s).
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Expand the Stereo Output section in the Inspector.
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Enable Enable Stereo Output.
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Select a Stereo mode from the dropdown (see the Options Explained section below).
6. Route projectors to outputs
Open the Video Routing matrix. Check the cell that connects each stereo projector to its corresponding GPU output.
For a two-projector passive setup, each projector routes to a separate output. For a single-projector active 3D setup, one projector routes to one output — the stereo mode handles the left/right packing.
Options explained
Stereo output modes
These modes are set per output in the Stereo Output section of the Output Inspector.
|
Setting |
Description |
Values / Range |
|---|---|---|
|
Enable Stereo Output |
Activates stereoscopic rendering on this output. |
Checkbox |
|
Number of channels |
Number of stereo channels rendered per output. Currently fixed to Stereo 2 (left/right). |
Mono, Stereo 2, Stereo 4 |
|
Stereo mode |
Determines how left and right eye frames are packed into the output signal. See details below. |
Dropdown: WhiteLine, Active3dStereo, Line Interleaved, Column Interleaved, Side-by-Side, Top-Bottom |
Stereo mode details
|
Mode |
Description |
Use case |
|---|---|---|
|
WhiteLine |
Frame-sequential stereo with a sync pulse encoded as a white line in the output image. Left-eye frames show a short white line (1/3 width) at the top; right-eye frames show a full-width white line. An external 3D sync distributor reads these lines to synchronize shutter glasses or projector shutters. |
Professional two-projector installs with external sync hardware (most common). |
|
Active3dStereo |
Native GPU quad-buffered stereo. Requires a GPU and display connection that supports stereo page-flipping (e.g. NVIDIA Quadro Sync with 3-pin connector). The GPU alternates left and right eye frames at the display refresh rate. |
Single projector with built-in active stereo, or setups with NVIDIA 3D Vision / Quadro Sync. |
|
Line Interleaved |
Alternating horizontal scan lines carry left and right eye data. Even lines = one eye, odd lines = the other. Non-stereo (2D) content renders at full resolution. |
Passive polarized displays or projectors with line-interleaved polarization filters. |
|
Column Interleaved |
Alternating vertical columns carry left and right eye data. Non-stereo (2D) content renders at full resolution. |
Autostereoscopic displays or lenticular screens that expect column-interleaved input. |
|
Side-by-Side |
Left eye in the left half of the frame, right eye in the right half. Each eye is rendered at half horizontal resolution. |
Projectors or displays that accept SBS 3D input. HDMI 1.4 3D frame packing over a single cable. |
|
Top-Bottom |
Left eye in the top half, right eye in the bottom half. Each eye is rendered at half vertical resolution. |
Projectors or displays that accept top-bottom 3D input. Common for satellite/broadcast 3D delivery. |
Projector stereo settings
|
Setting |
Description |
Values / Range |
|---|---|---|
|
Project Stereo Content |
Enables stereo channel selection on this projector. When enabled, the projector renders only the assigned stereo channel from any Stereo Channel Container or top-bottom stereo asset. |
Checkbox |
|
Use Stereo Channel |
Which stereo channel this projector renders. Channel 1 = left eye, Channel 2 = right eye (by convention). Channels 3 and 4 are available for Stereo 4 multi-view setups. |
Dropdown: Channel 1, Channel 2, Channel 3, Channel 4 |
Stereo Channel Container settings
|
Setting |
Description |
Values / Range |
|---|---|---|
|
Name |
Display name for the combined stereo asset. |
Text |
|
Channels |
Number of eye channels. Mono plays one asset on all channels. Stereo 2 expects a left and right eye asset. Stereo 4 expects four assets for multi-view setups. |
Dropdown: Mono, Stereo 2, Stereo 4 |
|
Top-Bottom Stereo Asset |
Flag on a standard asset (not the container) indicating the file contains top-bottom encoded stereo. Backstage splits the frame into upper and lower halves for left and right eye. |
Checkbox (per asset, in visual asset properties) |
Common Mistakes
-
Both projectors show the same eye — Project Stereo Content is enabled on both projectors but both are set to the same Use Stereo Channel value. One must be Channel 1, the other Channel 2.
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Left and right eyes appear swapped — Swap the Use Stereo Channel assignments between the two projectors, or swap the left/right assets in the Stereo Channel Container.
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Active3dStereo mode fails to enable — Backstage automatically disables stereo if the GPU cannot create a quad-buffered stereo swapchain. Check that your GPU supports stereo output and that the correct driver settings are enabled. A warning appears in the Log window when this happens.
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3D sync distributor receives no signal (WhiteLine mode) — Verify that Enable Stereo Output is checked on the correct output and that Stereo mode is set to WhiteLine. The sync pulse is a horizontal white line embedded at the very top of the output frame — if your projector crops the top pixel row, the distributor may not detect it.
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Content appears squashed in Side-by-Side or Top-Bottom mode — This is expected. Each eye receives half the output resolution in one dimension. If your projector expects full-resolution side-by-side (frame packing), use a different mode or ensure your content is pre-rendered at double width.
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Stereo not visible — projector shows 2D content — Project Stereo Content is not enabled on the projector, or the Sequence uses a standard (non-stereo) asset. Check both the projector and the asset configuration.
Tips
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WhiteLine is the most common mode for professional two-projector stereo installations with external sync hardware. The white line width distinguishes left from right: a 1/3-width line for the left eye, full-width for the right eye.
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Line Interleaved and Column Interleaved modes render non-stereo (2D) content at full resolution — no halving occurs. This means you can leave stereo output enabled and play 2D content without resolution loss on these modes.
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Capture card inputs (Datapath, DeckLink) have an Allow 3D capture checkbox in the asset properties. Enable this when your capture source delivers a frame-sequential 3D signal.
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The Stereo Channel Container supports any asset type that Backstage can play — video files, image sequences, NDI streams, Spout sources, and capture inputs can all be assigned as left or right eye content.
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For passive 3D setups using two projectors with polarizing filters, you do not need to enable Stereo Output on the outputs. Instead, configure each projector's Project Stereo Content and route them to separate outputs. The polarization is handled optically.
Related
Stereo Channel Container — Stereo Channel Container reference (asset properties and channel options).
Play 3D Content with 2 Projectors — Installation scenario: Play 3D Content with 2 Projectors.
Set Up a Projection Surface — Set up a projection surface.
Outputs — Outputs reference (all output types and settings).