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Airport Textures...

Questions and discussion about enhancing and populating the FlightGear world.

Re: Airport Textures...

Postby islandmonkey » Sun Jul 22, 2012 3:49 pm

A fragment shader is a file of code that is used to create shaders for 3D graphics. See \data\Shaders for some examples and http://en.wikipedia.org/wiki/GLSL.
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Re: Airport Textures...

Postby Thorsten » Sun Jul 22, 2012 6:29 pm

Sorry what do you mean by this?


You can't really get high resolution on the terrain with normal textures. Out hires textures have about 2 m resolution (2000 m base size, 1024x1024 texture sheet). If you want 10 cm resolution, you'd need 20000x20000 pixel texture sheets, and GPUs don't do that. If you make base size smaller, you get more and more tiling artefacts. The solution is to combine several textures on the fly to get hires textures without tiling artefacts. You also can generate the appearance of surface structures casting shadows without them really being part of the terrain mesh in the process. That's done by a fragment shader, and that's going to be the future of texturing for us.

This is an example of what you can get by combining base, transition overlay, detail overlay and a heightmap for the terrain roughness - about 10 cm resolution on terrain structures, a gritty look of the surface with the correct shading, transition effects on terrain slopes,...

Image

I'm quite sure the texture linked is done in a similar way. You can't reach the quality of shader-generated textures with a single sheet, shaders are very, very powerful tools.
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Re: Airport Textures...

Postby LukeaFG » Sun Jul 22, 2012 7:13 pm

This seems very interesting, So by overlaying, transitioning a texture you would get higher quality terrain? but wouldn't that be a fps loss due to the texture being used multiple times?
By the way is this the Shader based LOD system that you are working on? okay sorry for asking so many questions :P but I have one more. If using this technique is a fps loss at 10 cm how did these guys get 2 cm, would they be using the same technique?
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Re: Airport Textures...

Postby LukeaFG » Sun Jul 22, 2012 10:19 pm

Okay here is V1 of the airport textures to download, it includes improved concrete/asphalt taxiways/terminal floors and a edited grass texture:)
Hope you enjoy Download
Screenshots:
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fullterrain.com / orbX

Postby Hooray » Mon Jul 23, 2012 3:58 am

LukeaFG wrote in Sun Jul 22, 2012 7:13 pm:If using this technique is a fps loss at 10 cm how did these guys get 2 cm, would they be using the same technique?


I don't know how they are doing this, but I agree that the level of detail is definitely amazing and basically unprecedented, especially in flight simulators - it looks more like visuals from some first person shooter, with lots of hand-edited textures and 3D modeling:



On the other hand, please keep in mind that they are definitely not using FlightGear, so it's hard to say how all of that is accomplished, however it is almost certain that they are using lots of payware resources, such as textures, aerial imagery, but also proprietary vector data. Once you have that data, it is much easier to create compelling scenery: http://fullterrain.com/product_czst.html
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Re: Airport Textures...

Postby Thorsten » Mon Jul 23, 2012 6:22 am

This seems very interesting, So by overlaying, transitioning a texture you would get higher quality terrain? but wouldn't that be a fps loss due to the texture being used multiple times?


There's always a price to pay for better visuals. Either in terms of framerate, or in terms of memory consumption or both.

Overlaying textures 'on the fly' costs me 10% of framerate per additional texture. I *think* by doing this outside the rendering pipeline and pre-merging all textures into single sheets that could be avoided - but memory consumption of terrain texturing would increase by a factor 50 (?).

CZST as in the movie is done by massive hires imagery in addition to anything else - I'm guessing that scene takes a gigabyte-sized harddisk portion. If you're willing to sacrifice an enormous amount of memory for just a single scene, than this can be done fast. However, for Flightgear we're usually looking for solutions which make the scenery better everywhere, so we can't throw a gigabyte of data at 10 km^2 somewhere.

That

Image

is something we could probably do (i.e. I think I know how the shader needs to be arranged) and it wouldn't be so expensive:

* use a very hires, very-homogeneous grass texture so that it doesn't tile at all
* use a 2d noise function to alter the color to red-yellow in patches
* use a second noise function to blend patches of sand texture in
* use a third noise function with a directional bias to get the light-dark stripes which look like lawnmower tracks
... and that should be it - two base textures (grass and sand), three different noise patterns superimposed, it should even be reasonably fast
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Re: Airport Textures...

Postby LukeaFG » Mon Jul 23, 2012 7:05 am

Pre merging seems a good idea as the textures would already be 'set' if you know what I mean? To me it sounds good but I am not the expert :P


The CZST scene does take 1:05GB of space (I found that out here:http://www.flightsimstore.com/product_info.php?products_id=2102) which IS ALOT, I never thought it would take so much space, just for that one scene!
So trying to do this on the fly at 10 cms is very complex?

So we might be able to see grass like that in FlightGear then?
I could make the grass and the sand texture if there was going to be something like this in FlightGear.

If I am getting this correct, we could use your Shader based LOD system to get that grass effect?
Sorry for asking so many questions again.
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Re: Airport Textures...

Postby Figaro » Mon Jul 23, 2012 8:02 am

Luke,

have you tested the textures at an apt.dat 850 airport, such as Luxembourg ELLX or Gatwick EGKK? The taxiway lines on the pictures above are begging me to ask ;)


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Re: Airport Textures...

Postby Thorsten » Mon Jul 23, 2012 8:07 am

Pre merging seems a good idea as the textures would already be 'set' if you know what I mean? To me it sounds good but I am not the expert


Do the numbers... A texture sheet is 2x2 km and takes about 0.5 MB on the harddisk in compressed form, judging by the dds texture size perhaps 2 MB when decompressed and mipmapped in the GPU memory.

With a visibility range of 50 km, we see about 2000 such texture sheets in the scene. If we pre-compute them, each of them is different, so they need 2 MB each of graphic memory, i.e. we need 4 GB memory just to store the textures (!) - that's where pre-computing starts to look a bad idea.

So trying to do this on the fly at 10 cms is very complex?


Moderately so for natural landclasses - there it's just mixing based on noise terms and terrain gradient (I think the shader executes ~400 lines of instructions per pixel, but a lot of this is fog and light computation, the hires texturing itself is just 30% of the computation load).

If I am getting this correct, we could use your Shader based LOD system to get that grass effect?


We'd do this the other way round: For natural terrain which you mostly see from high altitude, we want the base pattern to be supplied by the base texture (forest clearings, different forest types, see a mixedforest texture). On top of that we want to dynamically add detail by mixing smaller patches of hires textures in.

For airport grass, the highest detail would be in the base texture already, and what we want to do is to add larger scale patterns on top of that so that it doesn't look like a flat green surface from the distance when the hires detail can no longer be seen. This wouldn't work so well for other landclasses - one has to custom-design it in many cases.

I could make the grass and the sand texture if there was going to be something like this in FlightGear.


If you can come up with good hires GPL-compatible textures, I'll see what I can do with it (might not be immediately, though...).
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Re: Airport Textures...

Postby LukeaFG » Mon Jul 23, 2012 8:18 am

@connect: Here are 2 screenshots at EGKK, it seems that there is no issue :D
Image
Image

@Thorsten: Ohh okay I think I understand a bit now, this is all very new to me so bear with me lol :P
If you can come up with good hires GPL-compatible textures, I'll see what I can do with it

I created the grass texture in photoshop so there should be no problem in the licence and the quality.
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Re: Airport Textures...

Postby islandmonkey » Mon Jul 23, 2012 10:50 am

There actually is one problem there - taxiway side markings aren't supposed to continue onto the runway. Only the middle yellow line.
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Re: Airport Textures...

Postby Gijs » Mon Jul 23, 2012 10:53 am

850 uses different textures. The lines you see there are "actual" lines. The fact that they run through on the runway is a mistake in the .dat file.
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Re: Airport Textures...

Postby islandmonkey » Mon Jul 23, 2012 10:54 am

OK. I'll chase up that.
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Re: Airport Textures...

Postby Thorsten » Fri Jul 27, 2012 5:17 pm

Did anyone place an order for hires airfield grass here?

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(here we have an effective resolution of 5 mm/pixel)
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Re: Airport Textures...

Postby Hooray » Fri Jul 27, 2012 5:41 pm

fascinating, but I keep wondering how we managed not to speak about the same thing during the last couple days, obviously ;-)
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