How we build an aircraft simulator: projection screen


    In order not to repeat my own mistakes, I decided to write how we build an aircraft simulator. Then, when everything is already completed, there will be no time to rake photos and videos, much will be forgotten, and indeed laziness.

    We have almost finished R&D with the new visual system for the simulator, which will appear in St. Petersburg this year, and I will tell you how the independent product turned out in the process.

    Picture to attract attention:

    Let's go ( carefully, traffic )

    In outline

    When we received the order for the construction of the Boeing-737 entertainment simulator for the St. Petersburg customer, the first thing we decided was not to step on the already tested rake.
    One of these rakes is called the X-Plane and Cylindrical Projection.
    The essence of the problem is that the functionality built into the simulator does not have sufficient flexibility to qualitatively reduce the image from three projectors on a geometrically not ideal cylindrical screen.
    Moreover, in the process of very emotional communication with the author of X-Plane, it turned out that he performed all tests of this function on a segment-spherical screen, and did not fully understand what we, in fact, want from him.

    In addition to this aspect, we realized that LCD projectors are not very suitable for our application - over time, colors and brightness “go”, and this means that the picture will need to be reduced in brightness and color all the time.

    We also decided to change the power structure of the simulator, and hide the supporting structures directly in the skin, therefore, a “collective farm” with a tension screen would not be possible, and the screen should be designed from the very beginning as part of a single power circuit of the simulator.

    And then we decided that it was not a sin to try a spherical screen made of fiberglass.

    Since the rule “no more than 10% of innovations” is clearly not for us, but we are crazy, not idiots, it was decided to make one screen on stationary supports in order to beat all possible jambs and crutches “on the ground”.

    The manufacturer of fiberglass cladding panels made us a set of panels and a ground power structure, which arrived in Moscow and was assembled in a hangar. It turned out like this:


    The screen consists of three fiberglass panels mounted on steel supports with wheels. In the simulator, the screen will be mounted directly on the supporting structures in the casing.
    The working surface is painted with special paint for projection surfaces. This paint contains some kind of magical additives, which slightly increase the contrast of the image and reduce the “engagement” of the gaze over the surface.
    One of the concerns was the joints of the panels, but the manufacturer managed to make the edges of the panels very high-quality and even, so that the joints are almost invisible.

    It is assembled and disassembled all the hours in two or three, which is just fine compared to our past screens.
    From TTX: diameter of about 6 meters, viewing angle - 220 degrees horizontally and 40 degrees vertically.


    Three Benq W1080ST projectors. Ordinary household DLP projectors, no frills. The only difference from absolutely everyday models is Short throw, that is, a short focus.
    The difference between the LCD and DLP is immediately visible - right out of the box, all three projectors shine almost equally, the pixel size is much smaller than that of the LCD. Resolution - 1920x1080.

    The projectors are oriented so as to ensure that projections from adjacent projectors overlap about 200 pixels, or 10% of the picture. Why this is needed will be clear further.

    In order not to pull expensive, heavy and uncomfortable HDMI cables, HDMI over UTP extensions have been used. In the A320, we used Hama extension cords, but they suddenly disappeared from sale in the Russian Federation, so something similar was bought. At first, there was a problem with one of the extension cords, so I used Hama from stocks, so it stayed.

    Space warmers

    This is both a song and a groan.

    When projecting onto a curved surface, the picture needs to be adjusted.
    In addition to geometric correction, it is necessary to “stitch” the image, because in the overlap zone two projectors shine on the same surface.

    At the very beginning, we considered three options:
    1. Software solutions that work at the level of the video card. There are a lot of such software, among the popular and by ear - Sol7 and Immersive Display.
    2. Hardware for stitching.
    3. Well, as a completely fallback option, we were mentally ready to return to the solution with three X-Plane and its scanty possibilities for stitching.

    Both solutions have Pro and contra.
    In the case of software, we are attached to the platform - I did not find sane cross-platform solutions, therefore, only Windows. In addition, part of the computer resources will be given to the stitching task. Plus software solutions - the cost, and the ability to automate the correction process.

    A hardware solution is more expensive, and much more expensive. In addition, the community of this solution is not great, mainly companies that implement multi-projection systems for presentation purposes.

    Unfortunately, we turned to “specialists” who, having no experience in such projects, provided us with hardware staplers from the Taiwanese company VNS. They are called Geobox G-104, look like this:

    What the G-104 does:
    1. Curvature of the picture by points;
    2. Color correction;
    3. Stitching with a gradient decrease in brightness.

    There is only one problem - this piece of iron did not solve our problem.

    In order for it to work, it was necessary to either pass video streams for all three projectors through one piece of iron (and “experts” did not offer us such pieces of iron), or it was necessary to overlap the image at the level of the video card. Existing AMD’s Eyefinity and 3D Vision Surround technologies for conventional gaming video cards do not.

    After the failure with the iron solution became apparent, the “experts” nevertheless found a way out: they suggested we buy and use a professional AMD Quadro K5000 card - it is possible to overwhelm the drivers for it. But by the time the error was acknowledged, for two weeks now we had been looking at the fruitless attempts of the “specialists” and decided to refuse their services. In addition, the performance of the K5000 did not inspire confidence in applications such as X-Plane. In general, now we are looking for buyers for two sets of G-104. "Not useful."

    As a result, we switched to a software solution, and, after analysis, settled on Immersive Display Pro.

    I will not describe here the procedure for reducing the image using this software and webcam, it is quite obvious. If someone runs into difficulties, I will be happy to answer in PM or comments.

    Key points when using this software:
    1. Works only under Windows;
    2. Requires Aero to work;
    3. It is impossible to do without manual work with a laser level - the image will be crooked, although this does not affect the perception of the picture with the cerebellum.

    The result is that on the KDPV. As the first running application, I tried Google Street View

    Configuration and Architecture

    So, as a picture generator, we have a regular i7 gaming computer with AMD R9 290X.
    Three HDMI <-> UTP <-> HDMI converters are connected to the video card.
    At the driver level of the video card, a virtual display with a resolution of 5760x1080 is assembled.

    Immersive Display Pro is launched on top, which produces image warping and stitching:

    To configure everything, the Immersive Calibration Pro tool was used, which almost automatically makes warping and correction using an external webcam (and the resulting file which slip in Display Pro). In the course of the settings, such funny pictures are formed on the screen

    It remains to try to find a video with a resolution of 5760x1080. Until now, I only found videos from games on YouTube, but our Internet hardly passes such a resolution, so we watch for five seconds - we wait 25 when it gets up.

    What to do next

    After everything worked out, it became obvious that the screen itself was a product. There are games, and viewing infographics, and video (though it’s not clear where to get such video content).

    Recently, an idea arose to try to run 3D on the screen. A quick look at the Internet showed that the task, generally speaking, is being solved, but on NVidia, and with AMD, the people did not succeed, but we will try. We don’t want a banal anaglyph, we want shutter glasses right away.

    Well, then, if it works with 3D, it will be possible to complement reality and get something similar to the first 15 seconds of the video:

    By the way, since this venture has no commercial value, if someone has a desire to play augmented reality on such a screen, we are welcome.

    Thank you for your attention, and I will be glad to answer questions!

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