Material Taxi_Grass doesn't always blend well when "ground merging" is enabled

Version: SU/AAU/WU XX - 1.XX.XX.X SU 15 -

Frequency: Once/Rarely/Frequently/Consistently Frequently

Severity: Low/High/Blocker Low

Context: What package? In edition or mounted from Community? In main menu or in flight? etc… Not sure what “edition” means in this context, but this is happening in the scenery editor. I first discovered editing multiple World Hub airports, and then in conversation with Rotornut44, below, realized that it relates to the grass texture used by the World Hub and not all grass textures. (Or at least not in the experimentation I did.) The World Hub uses the texture Taxi_Grass, so .

Bug description:
I don’t have to tell anyone here that we use aprons to remove unwanted aircraft and other things from the aerial. There are times when I would like to have ground merging, as it makes for a more textured experience. (Grass aprons without ground merging sometimes look like AstroTurf.)

Unfortunately, if you enable ground merging in the World Hub or when using the texture Taxi_Grass under certain circumstances, the falloff does not look good at all. Below is a picture of an apron at LSZR, auto-generated by the AI system that creates the world. To my knowledge, all of these aprons have “Ground merging” enabled, and they are often very easy to spot, as the falloff does not merge with the surrounding aerial very well.

Repro steps:

World Hub version:

  1. In the Scenery Editor, place a grass apron on grass somewhere.
  2. Click the apron, and colorize it.
  3. In the properties, set the falloff to some non-zero value and ensure that “Ground merging” is enabled.

Non-World Hub version:

  1. In the Scenery Editor, place an apron on grass somewhere.
  2. Click the apron, and change the material to Taxi_Grass and colorize it.
  3. In the properties, set the falloff to some non-zero value and ensure that “Ground merging” is enabled.

Expected result:
The apron blends reasonably well with the surrounding grass.

Observed result:
The apron has a very clear border where the falloff is.


Square apron at LSZR at 47.486842, 9.551291 covering up an airplane on the grass:

Properties of that apron (note that this is the World Hub version, with the falloff being -1 m, as all auto-generated aprons are…it happens with a value of -1 or a positive falloff value):

Lines are gone when you disable “Ground merging”:

Video showing ground merging being disabled:

Stripped-down World Hub project with only one apron, the one in the pictures above: (6.9 KB)
(I don’t know if we’re allowed to share the XML from World Hub projects, so this is nothing but an empty World Hub airport project with one apron in it.)

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Just out of curiosity, what happens when you set the falloff distance to a positive value? I have never used -1 for an apron falloff. I have only ever seen that used for the default runway terraforming value…

I would also use a priority greater than 0, just for good measure.

I have covered up a few things with aprons here recently, and I’m pretty sure I have ground merging turned on. Not seeing this outline unless its what I mentioned above or just a localized issue.

Same deal with a positive value. It just happened to have a negative value because this is a World Hub airport, and 100% of all default airport aprons I’ve seen have a falloff value of -1. (I have no idea why.)

Actually, come to think of it, since this airport is not published yet (I haven’t even submitted it), I’ll bet you could go into the sim and go to LSZR (without the bespoke LSZR from Microsoft installed) and visit 47.486842, 9.551291 and probably see that outline in the grass without turning on dev mode.

I’ll try to remember to post a screenshot tomorrow with a positive value.

Please correct me if I’m wrong, but my understanding of priority is to ensure that something with a higher priority has a higher chance of displaying over something with a lower priority if the engine decides it needs to make some cuts for performance reasons. I would think that if I’m actually seeing it, it doesn’t need a higher priority for the purpose of demonstration.

If I have a chance, I’ll try to make a very simple airport with nothing but an apron in it and share the XML here so others can take a look.

(Love your work, by the way. I have a few of your airports.)

I’m not sure of the exact reasoning, I just remember reading something in the SDK that states something about priorities set to 0 not being guaranteed to have priority over default. Or something along those lines. Just good practice even though I have used 0 in the past and never have ran into an issue.

The suggestion was more to rule it out completely, but you’re probably right in that it shouldn’t matter if you can see it in dev mode.

I tried using -1 on some of my aprons as well and it looks like it just does a 1 meter falloff. Interesting.

Thanks a bunch! Glad to hear that you enjoy them!

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You know what? I’m kind of embarrassed about this, but this appears to be texture-specific. I’ve been heads-down in the World Hub for months and I assumed that this would be true everywhere, and that’s looking like a mistaken assumption.

Before I give more details, I want to mention two things:

  1. I verified this at the default airport, and indeed, if you park at LSZR ramp 3 (labeled in the below screenshot), you can see the bad blending at work (with a red rectangle around it). This is the LSZR without the bespoke LSZR installed. (Somebody made an awful apron in the bespoke LSZR. It doesn’t look like this.) I can give more examples as I work through other airports. I see this all the time.

  2. I tried this with a positive falloff for the same World Hub airport as before, and it’s still the same result:

Okay, on to some new findings:

The World Hub only has one kind of grass texture, and it’s Taxi_Grass, and that may be the culprit. I have some new screenshots. This is the same airport , but now as a “regular” airport instead of a World Hub airport, using Taxi_Grass:

Ground merging on:

Ground merging off:

If anybody would like to try this out, I have a .zip file of my project at LSZR: (7.0 KB) There’s only one apron there, so it should be pretty easy to find it.

Interesting. I just tried that same grass material at my airport and still don’t get that with ground merging on or off, or no matter what I set my priority or falloff distance to.

I was able to get a similar artifact (though, I don’t think the same) by turning on Force draw above runways. Though, you are not using this.

You might see if it does it at another airport far away, if not it could be location or color specific. Another thing I thought of is maybe its a DirectX 11 vs 12 thing. I’m pretty sure I’m on 12. Not sure what you’re running.

Strange for sure.

Unfortunately, I’ve seen it at a ton of airports. I’ve touched 18 airports in the World Hub so far (15 submitted) on three continents, and I’ve seen this happen in probably ⅔ of the airports I’ve done. It’s annoyed me enough that I had to submit the bug report, haha. Unfortunately, because I’ve fixed it in all of these airports, I have to go out seeking new examples, so I don’t have a ton of examples to present right now. (And I’m also on DX 12.)

But here’s one from an airport that’s near and dear to my heart: PATK. You might’ve heard of this airport. :wink:

In the base sim (i.e., not the Emerald Scenery PATK), here are two squares that you can pretty easily tell are aprons drawn over some ground clutter. I’ve included the airport beacon in the picture for context so it’s easy to figure out where they are:

I pulled it up in the World Hub, and sure enough, it’s the same thing as I’ve seen elsewhere: In the World Hub, all aprons, as far as I can tell, have that -1 falloff, but even if I change it to a +1 falloff, it’s the same thing. And ground merging is enabled.

When I take off ground merging, the falloff is a lot better:

Now, when you un-check “Ground merging,” is it perfect? No. But that’s because the AI-based system that auto-generates all the airports picked crappy colors to represent the grass. But those lines are not visible anymore:

I don’t know how much the SDK team wants World Hub airport XML being shared, even though when the World Hub launches, everyone’s going to have access to the XML. But in deference to any concerns they may have over that, I deleted everything out of the project except for these two aprons. Please feel free to open up this stripped-down project and take a look: (7.0 KB)

Or at my stripped-down LSZR: (7.0 KB)

I’ve updated the initial bug report for this, seeing as it’s not as black-and-white as I originally thought it was.

Here’s another addition. These are both aprons that are at the default airport CPT2 at the threshold of runway 06. I’m looking at it via the SDK World Hub airport. But until the June 2024 AIRAC cycle is published, one can go to CPT2 airport and look at these:

(After the June AIRAC is published, these will hopefully become invisible because I shrank them and set “ground merging” to FALSE.)