Layering

[Helli]

Hello everyone.

I am the guy, who took over in 2009 the task of editing and updating the ADE Manual, which was written by Bob Keeshan some ADE-versions ago.
Many things have changed since then, necessitated by user requests and most of all by Jon Masterson's creativity

One of the areas of never ending discussions was - and still is - "layering", both in ADE and FS9/FSX.
The last and very significant contribution was offered by Jon himself in http://www.fsdeveloper.com/forum/showthread.php?t=426274&highlight=layers

I find myself now confronted with the task to incorporate all this wisdom into the Manual in a concise, precise, short, but still readable format.

I did my own research for this. And it turned out that the data are more suitable for a lengthy Tutorial, than for a condensed Manual in Bob Keeshan's style and tradition.

I therefore take the risk and present here all my findings, open for everyone, open for criticism, open for ridicule.
And I hope that you all do just all that.
Please bear in mind that English is not my native tongue - don't hesitate to point out and correct all my Teutonic creations and aberrations.

Here we go
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The problem of "Layering" in airport design raises its ugly head when- and whereever airport elements overlap each other or have to be placed on top of each other.
The problem is made more complex, because layering is slightly different in ADE9 from FS9 and in ADEX from FSX and in some cases both ADE/FS-versions differ from each other - yes, it's quite a mess.
In ADE it is a question of visibility, in FS it is a question how the Simulator represents the results of the designers efforts, which not necesserily fulfill always the expectations .

The method for bringing order into that chaos is Machiavellian: create a hirarchy where each element has its place.
In FS the ACES generated a (not always) logical layer order, in ADE Jon Masterson allocates layer numbers to each airport element.
Jon's approach has the beauty that the numbers can - within limits - be changed, whereas the FS-system is frozen solid. Three cheers for the ACES.

The ugly head of layering is based on the fact, that airport elements are so very different from each other.
.... - ... in ADE they are all visible (of course), in FS some are invisible (NDB etc.).
.... - ...Some are three-dimensional, some are flat (two-dimensional)
.... - ...Of the flat objects, some are visible in FS (helipad, aprons etc.), some are not (navaids).
.... - ...Of the flat objects some change the airport terrain (vectors, Polygons)

That is why I differentiate in the following between the types of airport elements.
-----------------------------------------------------
Let's tackle the ADEX/FSX-situation first.

(1) RUNWAYS
No airport without runways

In the context of this discussion here, runways are the easiest problem.
First they rarely sit on top of each other in such a way, that they obstruct visibility (in ADE).
And second they have both in ADE and FS the same hirarchy, based on their surfaces.

Figure 1: List of layer numbers for Runways

From this table it can be seen, that the surface "Concrete" in both ADEX and FSX is the top guy, whereas "Dirt" is pretty low on the totem pole.

Figure 2: Runways in ADEX........................................................Figure 3: Runways in FSX

I think, these figures tell the story.

(2) TAXIPATH
Taxipaths are a difficult proposition, because they, together with taxi points, have more than one layer to make them work in the display:

Quoting Jon Masterson:
"There is a layer that shows the taxi point as a colored spot and one (lower) that shows the surface. There is a layer that shows the colored line representing the path (that can be selected etc) and a lower one that shows the surface. Points and lines are near the top of the pile when it comes to getting drawn; surfaces are lower down. Point surfaces need to overlay path surfaces otherwise the taxi network does not get drawn properly. Junction markings are in yet another layer. Messing these up would cause a lot of unexpected issues."
That is why taxipaths have just one fixed layer number, namely "5", which cannot be changed.
But then, how is layering done for Taxipaths?
In ADE it is simple: First In Last Out. The last Taxipath drawn is on top, the first one is the low guy. And you cannot change that. But that really does not matter, since Taxipaths are not supposed to sit on top of each other. That makes individual editing easy and feasable.

Figure 4: Taxipaths in ADE

In the example of the figure above, the "Tarmac"-taxipath was added first and the taxipath "Gravel" was the last, putting it on top of everything.

In FSX it is different.

Figure 5: Taxipaths in FSX

Here the "Tarmac" is on top and "Concrete" is at the bottom, because
FSX uses for Taxipaths a layering hirarchy, which is listed in Fig. 6 below:

Figure 6: List of layer numbers in FSX for Taxipaths

(3) Aprons
For aprons the situation with layering is identical with Taxipaths (see above)

(4) AIRPORT Objects with a Range of Layers
The list of objects, which can be added to an airport and which can cause a problem when they sit on top of each other, is pretty long. (You can see them by using the "Context Menu" (right click) and there the option "Add".)

But there are much more.
For all of them Jon Masterson has introduced a clever layering system.

There are 150 drawing layers where 0 is the top (anything in 0 will be drawn over all other things). Each different object type or display element is assigned to a set of layers.
There are three numbers provided for each - a minimum layer, a maximum layer and a default layer (where something gets drawn when you create it).
For example: ............LibraryObject ...4,69,39
This means that a library object can be drawn in any layer from 4 thru 69 and when you create one it will be drawn in layer 39. Re-ordering a library object in the ADE display can be done between layers 4 and 69. Thus a library object cannot be drawn over something in layer 3 or below something in layer 70.

The following table contains all three values per airport objects.

Figure 7: List of layer numbers for Objects

The main use of layering of airport objects is for the designers work in ADE.
In the ADE display objects frequently obscure each other.
A classical case is, where the "Tower Viewpoint" is placed on the same spot as the "Airport Reference Point" (ARP) and on top of this a "Tower" scenery object is placed.
In FSX this case does not pose a problem, because ARP and Tower Viewpoint are not displayed there.
But in ADE the actual tower building, having the biggest footprint, makes any access to the lower objects and their editing impossible.
This can be solved in many cases by using the options in the "View"-menu together with the "Hide Object"-option in the Context Menu.
But changing the layer of an obscuring object with the Context-menu-option "Move Back/Move To Back" or of an obscured object with "Move Forward/Move To Front" solves the problem in all individual cases.

To demonstrate this, in the next picture a hypotetical case was designed in ADE.

Figure 8: Layered Objects in ADE........................................ Figure 9: Layered Objects in FSX

There is not much to discuss here. Whatever is done in ADE, FSX simply displays the objects as in real life: "big covers small".
By the way, in Figure 9 there is a "lucky shot" showing, that Generic Buildings do not necessarily always sit smack on the ground. This one doesn't! But this is a different construction site and will not be discussed here

(5) Layering of Terrain Vectors (Shape Vectors)

will be continued

yours truely
Helli

 

[scruffyduck]

Helli

This is a most excellent post. I am probably repeating you and myself in what follows:

Layers represent the drawing order of of objects. That is what covers what.

FS layers are primarily about surfaces - what surface covers what. This applies to runways, taxiways and aprons. It also applies to taxiways drawn over runways drawn over aprons. It also applies in that all airport elements get drawn over terrain elements and, with the new GP function, all GP elements get drawn over all airport elements.

A lot of confusion arises with folks when they want to place a surface of lower priority over one of higher. It does not work and the only solution is to cut out the higher to allow the lower to show through.

The sole purpose of ADE in relation to these three groups is to display them in the same order as they are displayed in FS - thus giving the user a more accurate representation of what it looks like.

There is also a fixed order for GP objects based on the GP-Layer that the user selects for them. Unfortunately ADE was designed so that 0 is the top layer while the system FS uses for GP objects has 0 at the bottom. ADE puts GP objects into a group of ADE layers and relates these to the GP Layer specified by the user.

Now the fun starts with other things - generally buildings etc are going to be on top of everything else. So simply ADE might just arrange for all this lot to be drawn over everything else with the highest drawing order (layer).

However this is where ADE diverges from FS. In FS you cannot say - oops that building is in the way, just move it under the apron for me...... Airport Designers however need sometimes to move stuff out of the way so that they can see what is under it. Most drawing tools allow you to do this. ADE provides a bunch of ways to hide objects either singly or in groups so that what is underneath can be seen.

ADE also allows the user to move certain types of objects up or down in the drawing order. This cannot be done for those elements with surfaces since this would allow the user to show in ADE something that does not happen in FS. So the sole purpose of allowing the user to move objects up and down the layer system (drawing order) is so that they can work on things that would otherwise be obstructed by the object being moved.

There are contraints placed on the range of layers these objects can be placed in - this is somewhat arbitary and controlled by the layers.dat file. Needless to say this results in some users wanting to change this, or in some cases just ignore it all together. The current beta actually allows users to ignore most of the contraints.

There are a bunch of non FS objects drawn in ADE such as background images, guidelines, helpers and so on - these have layers purely for ADE of course.

So where does this leave us. Well I think in the manual we should provide the minimum explanation of this - just enough that the user understands drawing order (layers) and how to change them. I would then be inclined to leave the more complex and confusing explanations to either a post here or to a tutorial.

 

[GHD]

Layering can be horrendously complex.

I find that judicious use of the view options together with "Hide object" simplfies things tremendously.

 

[Andrew]

OMG

Cheers,

 

[tgibson]

The sole purpose of ADE in relation to these three groups is to display them in the same order as they are displayed in FS - thus giving the user a more accurate representation of what it looks like.

But Jon, as you can see in the pics the order that FS draws taxiways and the order that ADE does is *different*...

 

[scruffyduck]

But Jon, as you can see in the pics the order that FS draws taxiways and the order that ADE does is *different*...

Then I have it wrong in ADE and I should put it right............... If someone will confirm to me what the correct order of taxi surfaces is from top to bottom then it can be changed in the data file

 

[Helli]

If someone will confirm to me what the correct order of taxi surfaces is from top to bottom then it can be changed in the data file

Jon

presently they get drawn in ADE by sequence of drawing, i.e. the first drawn is on the bottom, the last drawn is on top

Helli

 

[gadgets]

Jon, if you download my Adding Realism to your Airport tutorial from http://stuff4fs.com, on page 8 is a picture, actually a screenshot, of all taxiway surfaces drawn over each other. Unfortunately, I was unable to include it in this post.

Following is the associated text from that tutorial:

"Surfaces are drawn in the following order:
• CEMENT and CONCRETE (these surfaces appear identical)
• CLAY
• ASPHALT
• GRASS
• ICE and SNOW (these surfaces appear identical)
• DIRT
• CORAL
• GRAVEL
• STEEL_MATS
• BITUMINOUS
• BRICK
• MACADAM
• PLANKS
• SAND
• OIL_TREATED
• SHALE
• TARMAC
So, for example, on an ASPHALT apron with a CONCRETE pad, the pad outline should be drawn in the ASPHALT apron. The shape of the CONCRETE apron need only be confined to within the bounds of the other and cover the pad area."​

Hope this helps.

Don

 

[scruffyduck]

Thanks Don

I have downloaded the tutorial

 

[jvile]

Jon, if you download my Adding Realism to your Airport tutorial from http://stuff4fs.com, on page 8 is a picture, actually a screenshot, of all taxiway surfaces drawn over each other. Unfortunately, I was unable to include it in this post.

Following is the associated text from that tutorial:

"Surfaces are drawn in the following order:
• CEMENT and CONCRETE (these surfaces appear identical)
• CLAY
• ASPHALT
• GRASS
• ICE and SNOW (these surfaces appear identical)
• DIRT
• CORAL
• GRAVEL
• STEEL_MATS
• BITUMINOUS
• BRICK
• MACADAM
• PLANKS
• SAND
• OIL_TREATED
• SHALE
• TARMAC
So, for example, on an ASPHALT apron with a CONCRETE pad, the pad outline should be drawn in the ASPHALT apron. The shape of the CONCRETE apron need only be confined to within the bounds of the other and cover the pad area."​

Hope this helps.

Don

That list is incomplete based on the xsd file and a couple of textures are out of order based on priority. The following list is the taxiways and aprons for FSX ONLY. FS9 uses a different list priority.

Starting from top to bottom

Tarmac
Shale / Oil Treated are identical textures and have the same FSX draw priority
Sand
Planks
Macadam
Brick
Bituminous
Steel Mat
Gravel
Coral
Dirt
Snow / Ice are identical textures and have the same FSX draw priority
Asphalt
Water
Grass / Clay are identical textures and have the same priority
Concrete / Cement / Unknown are identical textures and have the same priority

If we look at the last texture concrete we also see that cement and unknown is listed. The same applies to Grass where Clay is also identical. We again see the same with Shale and Oil Treated.

In the picture Concrete, Cement and Unknown is the lowest priority. There is no color listing for Surface_Unknown in ADE so it turns a default black. The picture also shows 2 Grass but 1 is Clay



Based on my list looking at just the bottom 7 textures Water does not cover Asphalt or higher but does cover the 2 grass and 3 concrete textures. Disregard what you see in ADE as far as what covers what since that is what Jon is working on.



Runway textures in FSX have a different priority list.

Jon, are you going to also list/sort layers for FS9?

 

[scruffyduck]

Hi Jim and thanks. At the moment there is only one layer data file but I propose to make it version specific.

 

[gadgets]

Yes, Jim, you're right. I had asphalt and grass interchanged in my tutorial.

And yes, my list applies only to FS9. FSX didn't exist at the time of writing.

Otherwise it would seem our lists essentially agree. As for the adjacent materials with identical textures, their relative priority didn't matter to me since the result would always be the same anyway. I was simply trying to illustrate what one could expect with intersecting/overlapping taxiway textures and the accompanying picture - which I was unable to attach to the post but which I have forwarded to Jon separately - nicely demonstrates.

But if they have the same priority and one were to change one of the assigned textures of, say, Clay and Grass, then which would be displayed in FS if the two were to ever overlap?

Don

 

[jvile]

But if they have the same priority and one were to change one of the assigned textures of, say, Clay and Grass, then which would be displayed in FS if the two were to ever overlap?

The way ADE works (right now) is each texture is assigned a number.

Apron,Clay,117,117,117
Apron,Grass,118,118,118
Apron,Unknown,119,119,119
Apron,Cement,120,120,120
Apron,Concrete,121,121,121

In the above example concrete having the highest number makes it the lowest priority. Cement will overlap Concrete, Unknown will overlap Cement and so on. Any textures that have duplicates like Concrete, Grass, Ice, Shale, etc. you cannot see the overlap. If I want a concrete texture I can use 1 of the 3 since they are all the same.

 

[gadgets]

Sorry, Jim, I was asking about how FS would display different textures having the same priority, not ADE. I should have been clearer.

Don

 

[jvile]

Don

In FS9 and FSX I can't find a Apron Clay texture. I can't find a Cement texture or a Oil Treated texture. I think what is happening is when you select the Cement or Unknown it calls for the Concrete texture which that one does exist.

That makes the actual apron look like a single texture drew it. In the picture I used all 3 concrete textures (ie cement and unknown) and overlap them with intentional misalignment. All the squares that make up the concrete blended straight as if a single apron was drawn. The same applied to grass and clay. I could not see a seam at the overlap.

 

[gadgets]

It was nearly 6 years ago when I wrote that document. I simply laid out vertical and horizontal, side-by-side taxiway segments and assigned each available material type to them.

Like you, I don't see any separate texture for Clay, Cement or Oil Treated. Perhaps the names are an inadvertent hold-over from an earlier version of FS. (FS9 was my first foray into FlightSim.)

So, it would seem we have a situation where there are two names for the same texture - in which case, there is no possibility of changing the assigned texture for only one of them. Thus, the situation I postulated can never exist.

I'm happy!

Don.

 

[glottis]

And then in FSX we come to vehicle paths
anyone done a test with these?
i generally only use Asphalt and Concrete, occasionally Bitumen and they seem to draw over everything except runways

 

[tgibson]

Hi,

The difference between surfaces that use identical textures might be the roughness of that surface? I seem to remember that Unknown is quite bumpy, for example.

 

[jvile]

And then in FSX we come to vehicle paths
anyone done a test with these?
i generally only use Asphalt and Concrete, occasionally Bitumen and they seem to draw over everything except runways

Ray

Taxiways and aprons pair up meaning they both use the same default texture and layer the same. If you look at my list everything covers concrete and most everything else covers asphalt.

The vehicle path is paired up with the runway textures (bad move on MS part). I am working on the list for runways / vehicle paths but will tell you this.

Concrete runways carries the top priority and covers all other runways, Asphalt is close to the top of the list also. Since the vehicle path is considered a runway texture in FS you will have to use the runway list that I post later today.

 

[jvile]

Helli

I hope this thread is still on target for all the questions you had in your OPost.

I am checking FS9 now for proper layering.

I am doing the runway layers in FSX and FS9.

I have all the polys on a picture somewhere in this computer.

etc
etc