Every now and then someone tries to set a taxiway in WED to “transparent”, and it pretty much never does what the author expects. Here’s a brief explanation of what’s going on.


“Transparent” is one of the many built-in surface types that runways can take on in X-Plane; more commonly you would pick asphalt, concrete, or grass. So what is a transparent runway?

The answer is: it is a runway with:

  1. No texture. That means you see nothing where the runway is. (This is fast by the way; we are not drawing the runway with a 100% clear texture, we actually don’t even place the polygons.)
  2. No physics. The runway does not change the physics from the underlying ground.

At this point a sane author is thinking: then what does a transparent runway actually do? Why have a no-op?

The answer is: user interface and lights.

  • A transparent runway is still a runway; and thus X-Plane can know “hey, there is a runway 3L at KXYZ airport.”  X-Plane even knows where the runway is (since the transparent runway has ends and a width) and can thus start your aircraft ont hat runway.
  • A transparent runway has approach lights and all other types of runway lights. A few of the common approach light fixtures with “rabbit” strobes are incredibly annoying to build by hand (you can do it, but you basically need a plugin, a gajillion objects, and super-human patience).

So the transparent runway lets you do the graphics and physics with draped polygons and leave the hard things (user interface and lights) to us.

The primary thing to note: the physics are up to you too, and the expectation is that you’ll do the physics with the same tool you’ll use for the graphics. So if you put a draped .pol file down, you can set its surface type (with the SURFACE directive) to match the visuals of the texture you are using.


Taxiways follow the same logic, and thus they are really quite silly.

  • Physics and graphics are up to you – the taxiway does nothing.
  • There really isn’t anything else to a taxiway; it isn’t part of the UI, and you can place taxi lights directly using light/line strings in WED.  You don’t actually need the taxiway polygon.

The fact that you can make a transparent taxiway in WED is actually a bug – the UI simply knows all surface types and does not have special code to say “hey, for a taxiway this is silly!”

What Transparent Taxiways Are Not

Transparent taxiways and runways are not a way to get the physics without the graphics. Instead, get the physics by putting a surface directive on your draped polygons.*

* There is one inefficiency here: if you have a huge draped orthophoto that covers a wide area, it will contain imagery that spans multiple surfaces: grass, concrete, etc.

Here is my suggestion: overlay a second polygon (with a repeating texture at very high res) with some kind of “grit” overlay.  Place this only on the areas with concrete (or asphalt, depending on the kind of grit you use) and set the overlay’s surface type to match the overlay’s appearance.  This way the polygons you must place for physics correctness at least add visual value too.

About Ben Supnik

Ben is a software engineer who works on X-Plane; he spends most of his days drinking coffee and swearing at the computer -- sometimes at the same time.

16 comments on ““Transparent” Runways and Taxiways

  1. Ok, well that does explain why I couldn’t get it to work. Thanks for the clarification Ben!

    Oh, by the way, feature request coming via Mantis… 🙂

      1. Hmmmm, I was able to post it last night, and as of this comment, it’s still there (Issue #0000756).

        Should I redo it at a later time?


  2. Maybe this is a pipe dream, but I think it would be interesting to have a checkbox in the rendering setting to make the autogen roads transparent. Then, if using good photoscenery and osm, the autogen cars would be “driving” on those roads. If this has been discussed before, I apologize for missing it.

    Yes, no, maybe?

    1. We are definitely NOT going to have a rendering option to make roads transparent. 🙂

      There is a real authoring idea here, namely that the vector cars can match an orthophoto. RealScenery already does this, I believe. The way they do it is the right one: they include orthophotos and vector roads; the vector roads reference a custom road type set (.net file) that includes cars but not vectors.

  3. Is good to know this.
    Now i understand, when use Go to Airpot, window you can see a small preview of the airport where you go, where the runways transparent read corectly, but transparent taxiway cant see it.
    Thank you lot for explication.

  4. Ok, this explains why I am having trouble making the ground smooth with invisible taxiways.

    If I understand correctly, it is currently impossible to make an invisible polygon that creates a smooth taxiing experience from within WED that is eligible for upload to the scenery gateway?

    Thanks, Jan

    1. Correct. Stupid q: under what condition would you -want- to do this? What graphics are providing the appearance of smooth pavement that -need- underlying physics?

      1. Not to trounce on Jan’s answer, but personally I’ve hit at least one Pavement texture (asphalt/concrete_#X.pol’s) that is included in the /lib/airport/pavement/ directory that does not smooth out things at all. Not sure which one, as I just switched to a different texture and the problem seemed to go away. Perhaps I’m using those incorrectly as well…? Should those go over the top of an existing taxiway and be used strictly for texture?

        Although, +1 from me for the ability to add a transparent polygon and assign it a surface attribute, but then, you already knew that 😉


      2. I tried to do this for small GA airfields that consist mainly of a huge grass movement area. Modeling this with the “grass” taxiway looks not so good, because of the very uniform and unnatural looking gras-taxiway-texture. Its ok for smaller areas, like runways or taxiways, but looks out of place as a bigger area.

        The texture being used inside airport boundaries in the Europe area looks much better, but is not smooth enough to taxi on. Thats why I wanted to put a “glassy” taxiway on top, to smooth it.


        1. Hi Jan,

          We can almost certainly make the grass textures on the runways look better using tech we used for the ground; please file a bug, and include the ground .pol that matches the ground type you would -like- to see, so we can examine how it was done.

  5. The runways remind me of a little feature I want to ask for. It would be great if I could turn off the taxi guide arrows when using ATC (like switching on/off our flight path).

    Beside this – thanks for your great work – I never was really happy with any flight simulations – with X-Plane 10 I am.

  6. Hi, first of all, thanks for a really nice job, I do apreciate what you and other laminar programmers are doing, I just have a request, since a lot of people like me uses this software for homemade flight simulators, I think we all have this same problem with the gps, would it be possible to run the Garmin 430/530 screen in a second monitor? thanks for reading this comment =)

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