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FSXA Scenery Object Offset

  • Thread starter Thread starter Aviasim
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Aviasim

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Hello All, hope I have posted this in the correct place but here goes...

The problem is that my scenery objects, which are buildings, do not appear to be placed correctly.

The Details....
I have my custom ground polygon matching my photoscenery (resampled) pretty much perfectly, usually, I would place my buildings above my ground polygon in 3ds and export as a seperate file, but using the same co-ordinates as where I placed my ground polygon.

Well basically, after doing it this time 'round, FS doesn't seem to want to play ball and my buildings seem to be offset and scaled down slightly. I have not changed or altered anything, I have been doing it this way for years without issue until now.

The buildings in question have indeed been corrected for the curvature of the earth.

The buildings I am talking about here are north of my reference point which is the center of the runway, the offset here seem to bring my buildings south by a meter or so... with that in mind, I have the terminal area to the west of the reference point, again, exported the same way I always do, but these buildings seem to bring my buildings further east than they need to be... and same for the buildings to the south of the ref point - basically all files, though they are in correct place in 3ds etc, all seem to come closer to my ref point in the sim

The AFCAD file and SBX flatten are at the same altitude - I have tested this over and over again trying all the tricks I know to no avail.

Just to clarify.. the scenery I am trying to place has no attached effects at all other than the curve correction, all models in the scene I am exporting have a FSX material applied, checked all DDS textures.. nothing is wrong there... I am utterly lost as to what may be causing this

Anyone here had the same problem? did you get it fixed? if so, I would be more than grateful to hear how as this has never happened before and my procedure and software has not changed other than newer versions of MCX as they are rolled out
 
Is your modeling program Blender, Autodesk 3ds Max or Perhaps SketchUp with a 3ds export? All you say is "3ds." Also you should try to be very clear about procedure beyond, "it's not working the same way I've been doing it since the dawn of civilization." Please try to be clear about what comprises this same way.
Without knowing what software you're using and having no real indication of your procedure, one can only guess. You write about multiple building offsets. I get the impression that you are trying to compile an entire airport as a single scenery .bgl. If that or similar is the case, an immediate solution would be to break this scenery .bgl up into smaller models and use placement .bgls to establish location. I suspect the cause of the problem is the fact that this is the largest project you've attempted thus far.
 
Hi Darren:

If you used a aerial imagery background image in ex: 3DSMAX for 3D modeling of the buildings in question, and that aerial imagery background image- or a higher resolution version of same- was sliced to create your Ground Polygon tiles, IMHO, it is very likely that your GIS "projection" was a "Spherical Web Mercator" type (aka "Flat Earth" in ArcGIS legacy syntax) to provide a non-warped texture image to work with.

That projection (which is close to- but slightly different from- Universal Transverse Mercator (aka "UTM") and other modified Transverse Mercator-type local planar projections such as the Ordnance Survey British National Grid projection, are inherently not accurate for calculation of Geographic coordinates at distances beyond 1 Kilometer from a given point within a particular grid tile, so IIUC, at EGNT, if the ARP was the central RefPoint for G-Poly tiles, and the terminal building placement was computed relative to that same RefPoint when converted via MCX, one might expect spatial positioning errors when imported and converted / placed via MCX.

https://communities.rics.org/gf2.ti...657_Map_Proj_Scale_Factor_1st_final_draft.pdf

http://www.fsdeveloper.com/forum/threads/brit_grd-to-wgs84.438229/

https://en.wikipedia.org/wiki/Ordnance_Survey_National_Grid


Custom photo-real aerial imagery land class compiled via FSX SDK Resample will be the most accurate in terms of size, shape, and positioning as the source files must be in Geographic (Lat-Lon) WGS84 projection, and after "mapped" to those grid coordinates, the aerial imagery tiles are re-projected and draped onto FS terrain grid vertices for Quads and Area Points by the FS rendering engine at run time

http://www.fsdeveloper.com/forum/threads/exporting-geotiff-lat-long.18566/page-2#post-236073


In ex: 3DSMAX, if "flat" G-Poly objects are segmented into individual objects no larger than 100 Meters in size by Lat or Lon, and are placed Geographically as groups of such objects with no object perimeter extending beyond a distance greater than 500 Meters (1/2 Kilometer) away from the RefPoint for placement of that object group, one 'may' be able to minimize inaccurate FS run time display positioning anomalies ...depending on its Latitude and Altitude position in the FS 3D world.


In ex: 3DSMAX, if 3D scenery objects are positioned relative to the Cartesian Origin of Axes (X,Y,Z = 0,0,0) at distances greater than 1 Kilometers, when compiled to MDL, that distance from the Cartesian Origin of Axes (X,Y,Z = 0,0,0) must be adjusted manually for the BGLComp XML-type scenery library object placement RefPoint on ground as Decimal Geographic Arc Degrees- rather than in Decimal Meters- in order to be displayed correctly in FS at run time, as placement will not be calculated based on physical distance on ground in fractions of a Meter, but rather as fractions of a Arc Degree offset from a nearby FS quad matrix terrain grid vertex.

This is complicated by the increasing mis-alignment of coordinate positions between a Mercator-type projection and a Geographic / WGS84 projection when displayed on ground in FS at run time, when 3D world positioning is offset farther North from the Latitude where FS quad matrix terrain grid "shape and size is closer to a equilateral 1:1 aspect ratio (EGNT is closer to the 60 Degrees North threshold where such mis-alignments become more visible).

http://www.fsdeveloper.com/forum/threads/qmid-question.438142/#post-752644


IMHO, placement of 3D scenery objects by import and conversion via MCX should only be performed "semi-automatically" when using 3D geometry positioned no greater than 1,000 Meters / 1 Kilometer (FS default 3D 'model units' are typically Meters) to the N, E, S, or W of the Cartesian Origin of Axes (X,Y,Z = 0,0,0 aka "central datum") of the entire 3D model file when exported from ex: 3DSMAX or any other 3D modeling application.

Otherwise one must resort to manual methods of BGLComp XML-type scenery library object placement for greater accuracy.

http://www.fsdeveloper.com/forum/threads/glue-buildings-to-surface.426393/


PS: When object placement offset is evident, one must also consider whether Draw Call Batching is active for MDLs, and if LODs or animation frames are "intended" to be used, whether they are working properly ...in the version of MCX which one is using. ;)

https://www.google.com/#q=site:www.fsdeveloper.com+offset+draw+call+batching


Hope this information helps with sorting out this scenario and methods for work-flow. :)

GaryGB
 
Last edited:
Rick, Sorry, I am using 3ds max 9, the airport I am doing is EGNT Newcastle, which is actually quite a lot smaller than previous airports I have done. I thought I explained the process but I will do it again;

I model my buildings in 3ds max 9
I then place over my ground polygon and export the .X file
I convert the .X file to .MDL via XtoMDL
I open the .MDL with MCX and add the curve correction using my co-ordinates that are the same to place my ground poly
I save the .MDL and re-open with MCX to convert and place wizard

EGNT1_zpszpu42uhv.png

This Image shows where my reference point is, from 0,0,0 to the center of the emirates tower in the middle is less than 500M

EGNT2_zpsmfj4john.png

This image shows that it is placed where I need it to be

In the sim, it is moved slightly south-east so the widest part of my tower is just on the edge of the concrete pavement that wraps around the tower
 
Ok to be clear, you have ultimately two .bgl's correct? A ground polygon and a set of models as a scenery .bgl, yes? I still think an adequate solution would be to break the model into smaller .bgl's. I understand you establish position based on the reference point, but you could arbitrarily pick targets, say the center of Emirates Tower being a new reference and go from there. I think it's faster than trying to figure out how to correct for the offset with your current procedure, but I may not understand the problem fully, because if you have been doing this consistently, it should remain so.
I guess another possibility is a change in the Earth curve correction algorithm, but you could test that using earlier builds of MCX. I will tell you that it would make me uncomfortable, bundling everything together and running it through MCX, relying only on coordinates for placement. I know it works for you, usually, but as Gary implied above, discrepancies abound. I use a manual placement tool, Instant Scenery 3 and I break everything up into individual objects usually. Everything aligns to the satellite because I shift, raise, or even tilt or scale it to do so.
Is there a reason breaking your scenery .bgl into smaller .bgl's would not work for you?
 
That is correct Rick. Well the time I have left to do this project, it seems I will have to use instant scenery method and place that way - I do not feel 100% confident running everything through MCX I must admit. I section out the airport every time I start a project, so I have north zone, south zone etc just to make things more manageable (personal pref). If I did not get this issue, I was planning to merge all buildings via MCX to one big BGL, apparently this helps performance a bit, same for other but similar things as well such as vegetation, signage etc. I also find IS3 can become difficult to work with as you are not able to see where exactly it is like you can in 3ds max, by that I mean, in FSX, in top-down view...the roof of a building will always be bigger than the floor.. placing these buildings individually though should not be a problem, it's just the bigger buildings such as the terminal building which would be a pain and next to impossible for me to line it up "perfectly" as I could in 3ds max "Top" viewport
 
I understand exactly what you mean about placement. I imagine your terminal is close enough to the center reference that you could use coordinate placement for the .bgl containing it and reserve manual placement for outlying objects that are most affected by the offset. These are just ideas, trying to provide an additional perspective.
Another thing you can do that is not so extreme as it seems is to edit the satellite image to match your placement. When you think about it, you start with the anomalies; planes on taxiways, shadows, trees, cars. I like to remove building footprints, because the projected photo never matches the actual building. How much harder is it to shift what remains? It's just another way to go that may be more efficient for you.
 
The sat image itself is only really providing texture to grassy areas inside the airport and roads etc surrounding the airport.. my ground poly does not use any alpha channels so all/most buildings are covered anyway.. the terminal is pretty small, but with the terminal is the 3d model of the landside roads/parking spaces that are elevated.. along with a tunnel so placing this as accurate as possible is quite important but I will play around with it. It mainly comes down to the fact I dont feel 100% comfortable placing things in a way I am not used to, as I mentioned, earlier draft exports had no problem and I've not had this problem elsewhere - I do think though that as GaryGB mentioned, with the airport being quite far north that may be why I am getting these strange offsets.

Are you able to clarify, say for example I have a texture sheet that is supplying say 100 models or so.. for example taxiway signs, if I were to place each taxiway sign via IS3, would each sign draw the texture so basically when all are placed, they take 100 drawcalls instead of 1?

One thing I will point out to you though, you mentioned you use IS3 to adjust bank/pitch if it's needed, be aware that upon restart, the bank and pitch of the model placement is ignored and will only be visible after the BGL is loaded again via IS3
 
I believe draw calls are measured only on a per-model basis, as an individuals impact on the overall scene. I don't think it's valid to say 100 iterations of the same taxi sign takes 100 draw calls. When IS3 places these hundred signs, it is really just the one sign = one draw call. Now if you want to extend that to different portions of the texture sheet, meaning the same sign with different symbols, I really don't know, it is supposed to be the same draw call still.
I understand tilting the model does not save to the placement .bgl; however tilting the model in the GUI of the sim is an easy way to see how to edit it's angle in MCX, which will save to library .bgl.
 
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