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D-ECHO Caribbean scenery edit?

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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Fri Jul 05, 2019 2:58 pm

wkitty42 wrote in Fri Jul 05, 2019 2:46 pm:talking about adjusting the terrain makes me think of the huge job that has been discussed a long time back where the terrain data is edited via a GIS database and editor... AIUI this is where the shape files come from, too... i've not yet spent any tme with my QGIS installation to fully grok terrain editing but i do know that i can layer in the shapes... just not sure about adjusting elevations... i would think so as there has to be some method of doing that to knock out the building spikes that some terrain data contains... so i guess this is one step further back than just terrain assembly...

Python is a wonderful tool for overcoming huge jobs that don't require runtime.

I guess my next quest is finding the format for these btg files.

The shapefile thing is what stopped me with TerraGear. Apparently, the person with the "custom shapefiles" took his toys and went home.

@legoboyvdip: A .hgt file?

Edit: Anybody wanting to follow along:
http://wiki.flightgear.org/BTG_file_format
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Re: D-ECHO Caribbean scenery edit?

Postby wkitty42 » Fri Jul 05, 2019 3:54 pm

i'm talking about deeper than that... not raster stuff at that point, AFAIK... hgt files don't even exist at the level i'm speaking of ;)
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Re: D-ECHO Caribbean scenery edit?

Postby WoodSTokk » Fri Jul 05, 2019 9:30 pm

SurferTim wrote in Fri Jul 05, 2019 2:58 pm:I guess my next quest is finding the format for these btg files.

The shapefile thing is what stopped me with TerraGear. Apparently, the person with the "custom shapefiles" took his toys and went home.

@legoboyvdip: A .hgt file?

Edit: Anybody wanting to follow along:
http://wiki.flightgear.org/BTG_file_format


The wiki side is mostly correct.
AFAIK the 'Number of Toplevel Objects' should be updated.
Actually is written:
Byte offset: 8
Type: unsigned short
Description: Number of Toplevel Objects
In files before version 7, the number of toplevel objects was interpreted as a signed short, leading to a maximum number of 32767 objects in a single file.

We should extend it to:
Byte offset: 8
Type: unsigned short (up to version 7) / unsigned int (version 10 and above)
Description: Number of Toplevel Objects


Thats one point i'm remember.
Can be there are more.
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Fri Jul 05, 2019 9:51 pm

Thanks for the head's up on the top level objects size change on v10. That would definitely throw off the file pointer or array index.
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Re: D-ECHO Caribbean scenery edit?

Postby legoboyvdlp » Fri Jul 05, 2019 11:11 pm

SurferTim wrote in Fri Jul 05, 2019 2:58 pm:The shapefile thing is what stopped me with TerraGear. Apparently, the person with the "custom shapefiles" took his toys and went home.


Actually, no - I'm sorry to correct you on this but this is the completely wrong idea. There was either a denial of service attack or else someone abusing the download in order to download all the files and redistribute them. As best I remember it was the FGMEMBERS group behind this. This meant that it went offline due to this abuse but it is still apparently available by contacting Martin on the mailing list (?).



A HGT file is a raster file that contains elevation data. The best source of this is Viewfinder Panorama's worldwide DEM 3" download.

I think it would be easier for you if you try to understand the present toolchain first as that will help you in any work you are doing ;)
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sat Jul 06, 2019 12:08 am

legoboyvdlp wrote in Fri Jul 05, 2019 11:11 pm:A HGT file is a raster file that contains elevation data. The best source of this is Viewfinder Panorama's worldwide DEM 3" download.

I think it would be easier for you if you try to understand the present toolchain first as that will help you in any work you are doing ;)

The "present toolchain" is what I have been searching for. Do you have any idea where it is? Can you edit the elevation data with it?
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Re: D-ECHO Caribbean scenery edit?

Postby WoodSTokk » Sat Jul 06, 2019 12:42 am

There is also a type change in 'Objects'.
Actually:
Code: Select all
Byte offset  Type               Description
------------------------------------------------------------
     0       char               Object Type (see below)
------------------------------------------------------------
     1       unsigned short     Number of Object Properties
------------------------------------------------------------
     3       unsigned short     Number of Object Element

Should be:
Code: Select all
Byte offset  Type                                Description
-----------------------------------------------------------------------------
     0       char                                Object Type (see below)
-----------------------------------------------------------------------------
     1       unsigned short (up to version 7)    Number of Object Properties
     1       unsigned int (version 10 and above)
-----------------------------------------------------------------------------
     3       unsigned short (up to version 7)    Number of Object Element
     5       unsigned int (version 10 and above)


Also at 'Geometry Objects', there is the line:
Code: Select all
Each element of the object is a list of tuples, containing one or more unsigned short integers in the following order:

should be:
Code: Select all
Each element of the object is a list of tuples, containing one or more unsigned shorts (up to version 7) / unsigned integers (version 10 and above) in the following order:
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Re: D-ECHO Caribbean scenery edit?

Postby legoboyvdlp » Sat Jul 06, 2019 6:33 am

SurferTim wrote in Sat Jul 06, 2019 12:08 am:The "present toolchain" is what I have been searching for. Do you have any idea where it is? Can you edit the elevation data with it?


No, you can't. TerraGear takes the data it gets and turns that into scenery. It doesn't modify the data.

You can use fg-from-scratch to compile TerraGear on Windows or else there are various downloads available on the forum. I found one that works reliably - I can zip it up for you tomorrow afternoon.
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sat Jul 06, 2019 11:16 am

legoboyvdlp wrote in Sat Jul 06, 2019 6:33 am:
SurferTim wrote in Sat Jul 06, 2019 12:08 am:The "present toolchain" is what I have been searching for. Do you have any idea where it is? Can you edit the elevation data with it?


No, you can't. TerraGear takes the data it gets and turns that into scenery. It doesn't modify the data.

You can use fg-from-scratch to compile TerraGear on Windows or else there are various downloads available on the forum. I found one that works reliably - I can zip it up for you tomorrow afternoon.

If one can't edit elevation data around an airport, how did this happen? How did the cliff at the approach end of the runway get there? I may be wrong, but that cliff edge seems to match the airport boundary almost exactly.
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Re: D-ECHO Caribbean scenery edit?

Postby BecOzIcan » Sat Jul 06, 2019 12:26 pm

Any area within the Airport Boundary is set at Airport Elevation, whatever the elevation data. Outside boundaries, the HGT data applies.
If no WED Boundary set, FG will reserve some space around the airport elements. Looks like it's your case on the screenshot.

See viewtopic.php?f=5&t=22556&hilit=boundary

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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sat Jul 06, 2019 12:52 pm

I also found this thread with both D-ECHO and wkitty42 posting.
viewtopic.php?f=5&t=29377
I don't know where they were using the --max-slope parameter.

Edit: If all else fails, I do believe I can write a Python app to edit the .hgt files to flatten or slope areas.
The --max-slope parameter is apparently used with genapt.
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sat Jul 06, 2019 1:49 pm

Yes, genapts850 uses the --max-slope parameter with --max-slope=0 being a completely flat airport and --max-slope=1 being an airport that *can*, if the hgt data demands it, have slopes up to 45° (100%=1). At least that is how I understand it. This occurs within the airport boundaries, as BecOzIcan mentioned, with genapts producing a cliff at the boundaries if the normal terrain elevation does not equal the airport element's elevation there
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Re: D-ECHO Caribbean scenery edit?

Postby SurferTim » Sat Jul 06, 2019 2:12 pm

Now we are getting somewhere! Are you using the --max-slope parameter when you compiled the scenery?

Do you think it would be better to modify the heights in the hgt files? At current resolution, that would be a 16 bit height value every 100 meters (more or less) both horizontal and vertical. The airport at St Bart is 800 meters long and about 200 meters wide. That would be editing 27 points to get the slope correct.

And if that is not enough resolution, I'm going to try changing the resolution from 100 meters to 30 meters. It wouldn't make the current values any more accurate, but you could really get to it editing it to match an airport (9 times the number of points).

Edit: Here is the 1 degree x 1 degree area that includes St Bart, St Kitts, and Nevis. It is 1201x1201 (100 meter resolution) jpeg generated from the hgt file for this area, converting height to color. The potential exists that an app could edit the height of every pixel in this image.
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Re: D-ECHO Caribbean scenery edit?

Postby D-ECHO » Sat Jul 06, 2019 3:21 pm

yes, it was used
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Re: D-ECHO Caribbean scenery edit?

Postby wkitty42 » Sat Jul 06, 2019 3:26 pm

SurferTim wrote in Sat Jul 06, 2019 12:08 am:
legoboyvdlp wrote in Fri Jul 05, 2019 11:11 pm:I think it would be easier for you if you try to understand the present toolchain first as that will help you in any work you are doing ;)

The "present toolchain" is what I have been searching for. Do you have any idea where it is? Can you edit the elevation data with it?

AFAIK, the tool chain only assembles... you have to go beyond the tool chain to get to the lower levels where editing can be done... that's the QGIS database and editor that handles that type of stuff...
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"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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