X-Plane 11/12

X-Plane 11/12 introduced a multi-view feature that significantly enhances its suitability for creating immersive visual displays using a single X-Plane PC and license. This feature allows a PC equipped with a multi-output graphics card to render each connected display in a separate window, with customizable content for each display.

Multi-View vs. Grouped Displays

It's important to differentiate the multi-view feature from running X-Plane on a single, large grouped display (e.g., NVIDIA 2D Surround, ATI Eyefinity, or Matrox TripleHead2Go). In a grouped display setup, X-Plane renders a single stretched view across one window, which severely limits the maximum field of view achievable from a single X-Plane instance.

The multi-view feature is designed for ungrouped display outputs configured in "extended desktop mode."

Configuring Multi-View Displays

When X-Plane is launched in an extended desktop configuration, each display can be configured independently:

Full Screen Simulator: This option opens a full-screen X-Plane window on the selected display.
Content Selection: The content for each window can be chosen from the "Default view" options, which include:
- "Forward with 2-D panel"
- "Forward with scenery"
- "Forward with 3-D cockpit"
- "Forward with HUD"

These options mirror those found in the "View" menu.

View Customization

Each view can be further customized in terms of:

Field of View (FOV): Adjusts the horizontal and vertical extent of the visible scene.
Visual Offsets: Configures orientation and look-at direction.

For immersive display setups using multiple LCD panels or projectors, the "Forward with scenery" or "Forward with 3-D cockpit" views are typically used.

Forward with Scenery View

In the "Forward with scenery" view, only the outside view is visible, with cockpit elements hidden. This is ideal for setups that incorporate a real cockpit or physical cockpit panels, where the PC displays are solely for the external environment.

Forward with 3-D Cockpit View

The "Forward with 3-D cockpit" view displays both the plane's 3D cockpit interior and the outside view. This is commonly used in mixed reality and interactive setups where both the cockpit interior and the external scenery are presented on the PC displays.

The viewpoint (or eyepoint) for both "Forward with scenery" and "Forward with 3-D cockpit" views is configurable per plane in PlaneMaker. By adjusting the FOV and offset settings for each display, users can create immersive, omni-directional visual setups using a multi-display GPU and a single X-Plane instance. Numerous tutorials and videos are available online that delve deeper into the multi-view features.

The "3-D Cockpit" View Anomaly

While "Forward with scenery" and "Forward with 3-D cockpit" appear similar and suitable for multi-view setups, the implementation of "Forward with 3-D cockpit" in X-Plane can prevent a geometrically correct view without additional adjustments.

Illustrating the Issue with LCD Designer PRO

To demonstrate this issue, we'll use LCD Designer PRO with a 3x1 display setup, consisting of three LCDs rotated 90 degrees each. The user's eye-point is positioned in the center of the LCD cube formed by the displays. For simplicity, the LCDs are assumed to have no bezels and are perfectly connected, creating an ideal setup to illustrate the difference between the two views.

For this simple configuration, X-Plane is set with a horizontal FOV of 90 degrees for each view. The lateral (horizontal rotation) offsets for the left, center, and right views are -90, 0, and +90 degrees, respectively. We'll use the default Beechcraft Baron 58 aircraft positioned on KSEA 16L.

Test 1: "Forward with scenery" View

When configured with the "Forward with scenery" view, the LCD displays show perfectly aligned outside views from the eye-point. The alignment is seamless, especially at the edges where images join, and the horizon lines remain straight.

Alignment with "Forward with scenery":

Edge between left and center LCD display: Perfect alignment.
Edge between center and right LCD display: Perfect alignment.

Test 2: "Forward with 3-D cockpit" View

When the "Forward with 3-D cockpit" view is selected with the same FOV and lateral offset settings, the views become misaligned, and the horizon lines "break" at the edges between displays. This distortion is more pronounced when the aircraft is flying or making pitch movements.

Misalignment with "Forward with 3-D cockpit":

Edge between left and center LCD display: Horizon lines are broken.
Edge between center and right LCD display: Horizon lines are broken.

Understanding the Asymmetry

This issue was reported and confirmed by X-Plane development team. X-Plane explained that this is a function of how X-Plane renders, specifically that the view frustum can be asymmetric in the "Forward with 3-D cockpit" view.

In essence, the vertical FOV above the midpoint (where the horizon appears) can be less than the FOV below the midpoint. This asymmetry is designed to provide a more useful view of the window and panel for users with a single monitor with a relatively small vertical distance.

External Views: The vertical FOV is symmetric.
3-D Cockpit View: The vertical FOV is asymmetric, with the split defined by the aircraft's author. This asymmetry causes the projection to fail to line up when the camera is at the midline of your 3-D scene.

This difference is clearly visible: the horizon in the "Forward with scenery" view is lower than in the "Forward with 3-D cockpit" view. This asymmetry is the root cause of the misalignments and geometrically incorrect views.

Solutions for Geometric Correction

Fortunately, there are two simple solutions to correct this asymmetry and achieve geometrically accurate views:

Method 1: Adjusting Vertical Fractional Offset in X-Plane

This method involves adjusting the vertical offset within X-Plane's view settings.

Start X-Plane: Select an FOV of 60 degrees and choose "Forward with scenery" mode. Mark the position of the horizon on the edge of your LCD display with a sticker or marker.

Select "Forward with 3-D cockpit": In the view settings, use the Vertical fractional offset value to align the horizon with the mark you made in the previous step.

This value needs to be applied to all view definitions (left, center, and right) for consistency. It's important to note that this value is dependent on the loaded X-Plane aircraft, so steps 1 and 2 must be repeated for each aircraft to determine the correct Vertical fractional offset value.

Method 2: Adjusting Viewpoint in PlaneMaker

Alternatively, you can make the adjustment in PlaneMaker:

Open PlaneMaker: Load your aircraft's .ACF file. (Always create a backup of your .ACF file before making changes).
Navigate to Viewpoint Settings: Select the Standard/Viewpoint menu.

Adjust SCREEN-CENTERS: In the Viewpoint screen, select Cockpit and adjust the SCREEN-CENTERS view center Y value until the horizon aligns with the "Forward with scenery" view mode.

Save and Reload: Save the .ACF file, then use the X-Plane Developers/Reload Current Aircraft menu in X-Plane to apply the changes.

Achieving Geometrically Correct Images

After making these adjustments to symmetrize the view, X-Plane will produce geometrically correct images across all LCD displays. This correction also applies to multi-projector edge blending visuals using the "Forward with 3-D cockpit" view.

For optimal results in both LCD panel and multi-projector displays, use the exported data from Immersive LCD PRO and Immersive Calibration PRO, respectively, to configure the views in X-Plane. Additionally, leverage the exported warping data to create 100% geometrically corrected images that precisely match your display or projector and screen configuration.