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arno

mini DTM runway project - sloped runways

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I was wondering if there are a few people here that would like helping me taking FS2004 to the next level.I've just finished a 20m mesh for NZ and the detail is just incredible. However, a side effect is that the flat runways look a bit stupid. I've been contemplating over this a while.My idea is to build a highres mini-mesh for the runways. I have a few thoughts on how this could be achieved, but the whole method needs testing and input from other bright minds in this forum. So I thought maybe I can get a group together to solve this.OK, here it goes. My idea really is to build something more advanced than just sloped runways, but runways that have a whole elevation profile, ie, they could be shaped arbitrarily, eg ___/ or __/_/_.Mostly as designers we wouldn't have a profile, but the SRTM may be of help, as it provides us at least with 75m point measurements. I guess, this is problem no1 that needs testing. Is SRTM really accurate enough to do this kind of thing (ie if the noise it to big we wouldn't model the actual profile, but the noise). I have a profile drawing of the Cook Islands and I can also crosscheck with contour lines and spot heights. I've done this once and it looks like for Ryan's Creek in NZ SRTM is nice supplementary data.The real challenge though is to draw a non flat runway over the terrain, I see that this can only be done by mixing gmax and mesh.The mesh alone poses a few problems. Since it uses CLOD it changes with distance which may be hard to work with. A work around would be to define the whole runway with lots of little flattens (style 3). This way one could build a small micro mesh that is stable.Then one needs to import those point locations into gmax (we know the location of the grid points, so it should be possible to build some sort of automatic approach for this). With the help of the points one can then build a mesh in gmax and draw a runway on top. This also has the advantage of being able to draw nicer runways or runways with rounded ends, etc... Then one would load the gmax runway on top of the mini mesh. The gmax runway would show the hard surface, the mini mesh would actually supply the ground resistance.I have no clue if this can be done without getting z-buffer fighting, and I don't know what happens if we take off from (or land on) indulated runways, but I think it may be worth to give it a shot. I'm sure that if we split the work we may actually get this working.Any takers?Cheers,Christian

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Hi Christian.As long as gmax is used, why not clone the surface and make an attached platform... no need to harden the surface.Dick

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Hi Christian,Interesting, I certainly will follow this (and help where I can).Dick, the platforms in GMax are not really suitable for this. If you use too many in one area you get strange crashes of FS on exit. And also there is a limit of the amount you can use in one MDL file (compilation will fail).So I don't think the platforms can be used to make very detailed local mesh. I think it would be better to let the mesh scenery do the altitude and then have your GMax model follow the shape of the mesh very well. The visual maybe needs to be put 10 cm above the mesh or so to prevent zbias trouble. I want to test this idea for some time already, but haven't come to it yet.

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Hi Christian,neat ideas and a very worthwhile project!I once did a few tests of non-flat runways using sloped LWM3 polys as a base. The biggest drawback for me (not being an airfield designer) was the inability to incorporate AI traffic and the associated loss of the standard ground textures and objects. I can drape VTP2 polys over the surface (at 4.8m res) but adding taxiway lines etc. is another matter. Perhaps the GMax approach will make this easier though it won't help with the AI issue.Cheers, Holger

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Hi Holger,you can actually still use the default runways (yes, I did think this through). The only thing you need to do is to define the runway as transparent (which is possible). And then you can add the rest of the AI stuff.In regards to the actual surface, yes, VTP2 polys aren't suitable due to the low resolution. That's why I came up with the gmax idea. Once you have a gmax mesh, all you need to do is to draw the surface as a texture. This has actually some advantages of the default visuals as well. Some runways have turning bays and the side line follows the bays. You can't do that with the default. All you really need is to design some basic elements and then shuffle them together...Cheers, Christian

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OK, it looks like I got the right people interested :)I guess the next step will be for me to upload something to start off with. I'll see what I can come up with over the next few days.Cheers, Christian

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Hi Christian,I would be happy if I could get a walkaround for the simpler problem of a runway with different altitudes at the ends. The runway built-in command has the (X Y Z) parameter for the location of its center and the heading parameter. It would be nice if, in a future version of the sim, a pitch parameter was added.Therefore one needs to draw, with gmax or else, the complete runway elements, and call it using some kind of TransformCall().I hope to add to SBuilder the feature of handling slopped polygons which will help in creating slopped runways. Another thing that I would like to do is "breaking the 4.8m/pixel" in photographic scenery. My actual problem is that I am not able to read the Mesh. I am sorry for referring to SBuilder but it is easy for me to explain my ideas in its context. SB has a GUI to make photo scenery. Basically it slices (resamples) a background bitmap and generates BGLs that call VTP squares. As with the MS resampler the resolution is limited to 4.8 m/pixel. If I was able to read the altitude of the mesh I could also draw a list of textured triangles. I would use a test based on the distance to switch OFF the display of these triangles. Because the texture used for the triangles is the same as the one used for the "4.8 photographic" scenery I expect admissible display switching.So I am interested in following your project,Luis

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Hi Luis,That is also the idea we are trying out with the NL2000 Team at the moment. We are still in the progress of adapting our own scenery design tool for it, but what kind of trouble did you had with reading the altitude data?Some time ago I just loaded some altitude data in MatLab to make some plots of it. I guess it depends on the format used, but that data was very easy to read. Just a RAW file with altitude points.

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>... but what kind of trouble did>you had with reading the altitude data?Hi Arno,Say that I have a bitmap from which I want to generate "4.8m res" photo tiles. There is no problem. Either the MS resampler, SB or other, can create the photo tiles and calling BGLs.Supposing that the bitmap is an high-resolution one, I would like to create VertexList()s and DrawTriList()s to "break the 4.8m res". The trouble is that I am not able to read the altitude from the BGL. So I am not able to fill the VertexList()s. This has been discussed here before. Jim Keir once publish a programme that did just that but then it removed it. Regards, Luis

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Hi Luis,Ah yes, now I remember. For the NL2000 project we will be using custom altitude data as well (as the default mesh is not really accurate), so therefore we have not tried to read default BGL files.

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Christian,I ran into the same problem with my Tinian airfield. I ended up making the airstrip as a FSDS object with the runways broken into segments of about 100 feet long. I manually adjusted the points so that the runway would be the minimum distance above the terrain (ideally less than 1 foot). Nevertheless, the aircraft still sinks into the runway because it is really sitting on the underlying terrain.I have considered converting the runway to gmax and hardening the tops of each of the segments. Would that enable the aircraft to taxi on top of the runway?If so, could anyone walk me through the process of hardening a surface? I have read the MS explanation and am not quite "getting it". (I can't figure out how to display the box grid around the segments.)Phil

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Luis,Thanks. I'll take a look at that. I had considered overlaying the grid with a few sloping LWM Poly 3s but was never able to decide how many (or how few) Poly 3s to use and how to best fit them with the underlying terrain.Phil

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Misho,Looks interesting. Maybe I can import my runway into the mesh module. Are the surfaces on the object hardened?Phil

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YEs, they are, as this module produces a default style mesh. The surfaces will behave exactly the same as the underlying default meshMisho

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I wonder if hardening surfaces consumes a lot of processor time? I guess we'll find out and, if necessary, cut down the number of hardened surfaces.Phil

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The data for this is available but I'm not sure how easy it is to obtain for each country.As part of the airfield licensing each airport has to provide data on obstacles around the airport and, more specifically, within the the approach areas. Runway elevations are included in this and a profile shown of the changing gradients.In the UK the chart is called a Type A chart but this is not published - it is only used to provide data for the UK AIP. Other countries (Ireland is one example) are better and the Type A chart is included in the AIP data.The information is there - it is just a matter of luck whether you can get hold of it or not.An example of a Type A chart (for EGPC Wick, Scotland) can be found at http://www.caa.co.uk/docs/64/DAP_ACD_TYPEA_EGPC1.pdfEdited to add a further link..A full list of UK Type A charts can be found at the following page:http://www.caa.co.uk/default.aspx?category...=68&groupid=787I hope other countries are as helpful.

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Christian,I am not going to let this topic die :)I have converted the taxiways and runways on my Tinian airfield to gmax and am going through the slow process of cloning and hardening each of the segments. For example, each runway is 8500 ft long and has 66 segments. I have completed one runway and, so far, everything is working fine. The aircraft is taxing on top of the runway and is not sinking in - a major improvement. I will upload it to the board when I am done, so you can try out a "real world" runway.On a completely different topic, can you harden an animated object? For example, on a static aircraft carrier, if would be neat to add a little motion to the ship.Thanks,Phil

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>Dick, the platforms in GMax are not really suitable for this.>If you use too many in one area you get strange crashes of FS>on exit. And also there is a limit of the amount you can use>in one MDL file (compilation will fail).>Does anyone have any more info on this problem?I have made my local airport in Gmax with sloping runway, but I get the crash when exiting FS.The runway platform has 235 faces in Gmax.I have used VTP3 polygons to flatten the terrain under the runway.

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Sorry for the silence. I was busy with finishing 2 other projects and will be still for another couple of weeks, but then I'm quite keen to get back to this.My plan was to use LWM3 polys as surface hardening. In regards to how to do this, theoretically, you could have a poly every 4.8m if you're using the default LWM resolution. In practice, most contries don't publish mini DTMs for their runways, but SRTM is quite a good source for that. There usually are no builtup areas or forests right on the runways or aprons, so those heights should be fairly accurate. If you have extra measurements (eg the NZ AIPs give the heights at each end) you can calibrate the SRTM data easily...Misho, you're tool looks great. Would it be possible to integrate LWM3 poly into that, so when exporting one would have 2 data sets - gmax and LWM3 for hardening the slopes?The big remaining question is how does AI paths affect this? Has anyone tried? Some people say when adding a taxi layout for AI aircraft everything gets flattened again, which would be a serious drawback...Good work so far guys, I'll have a play myself shortly... looking forward to see what other people have come with so far.Cheers,Christian

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I just completed my AFCAD this morning for Davis-Monthan AFB and yes, if you add AFCAD taxiways everything is flattened at the elevation that you specify, sometimes badly so.For instance, I added taxiway Echo to the scenery, it goes a ways to the east and outside the default flat switch for the airport.The way I added it, the taxiway branches off outside the default flat area, so that one taxiway goes to the west end of an apron and the other taxiway runs parallel to the apron (about 50 feet away) and joins up with the east end of the apron. In between the taxiway and the apron, there is about a 40-foot high hill where FS didn't automatically flatten it.The possible way around this is the apron taxiways. I don't know if FS flattens them or not - if it doesn't, though, you'll have to have an AI AFCAD and then an underlying concrete layer. If FS does, then your sloped airport will not be able to handle AI.However, your airport would have to be without any taxiway or apron surface (though you could somehow do this, but not using AFCAD or XML).I believe X-Plane has sloped runway capability?

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>I just completed my AFCAD this morning for Davis-Monthan AFB>and yes, if you add AFCAD taxiways everything is flattened at>the elevation that you specify, sometimes badly so.Not good news. Just to confirm, it uses the airport elevation (taxiways don't have elevations specified with them)?>I believe X-Plane has sloped runway capability?Indeed it does, but i don't know how well it works.Christian

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As I wrote :), when you have too many FS will crash when you quit (so it is not really a super worse crash). I have tried a lot to find out why this happens, but it seems there is nothing you can do about it, it is just a bug in FS. The only thing that helps is to reduce the amount of platforms you use.

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