FSX Exporting model as FSX flatten

Hi Barry:

MCX imports the 3D Model and then exports it as a CVX vector flatten polygon; CVX vector flatten polygons modify any local terrain mesh.

CVX vector flatten polygons require an altitude attribute to be assigned for the intended position it is to occupy in the FS run time 3D world, or all vertices of the flatten object will default to 0 Meters MSL (not AGL). :pushpin:

You must assign an Altitude in the MCX placement dialog for the elevation MSL that you wish the flatten to be "placed" at in FS at run time.

If you are ultimately wanting to modify local terrain mesh in the vicinity of an airport, you must use a "blended" CVX vector flatten, which can be created in SBuilderX or ADE when either of those utilities are "connected" to a live FS flight session.

With the user aircraft positioned over each vertex of your CVX vector TIN object, FSUIPC can read and provide the in-sim "ground" surface elevation / altitude to be assigned by SBuilderX or ADE to each "sloped flatten" polygon vertex point at the outer border of the TIN where it meets the surrounding default or 3rd party terrain mesh loaded during that flight session ...allowing for a less obtrusive "blend" of surfaces.

If you would like further assistance with this process, feel free to inquire further. :)

PS: An alternative utility to modify 'local' terrain areas is Terrain Sculptor by Don Grovestine (aka "gadgts"):


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Hi Gary,

Thanks, I read out the ground alt using TcalcX and assigned the altitude in the object placement. That seems to work well.

I tried the same using a larger terrain mesh depicted in my first post for an island but without success. There are holes, spikes and other anomalies. Is this because it's not a blended flatten? There is no airport but there are hydro polygons which also have elevations (though this is in the ocean so elevation is zero).

lat/lon of the placement is 25.2499167, -77.8499830




Hi Barry:

Where did you get the original terrain source data, and which 3D modeling or FS utility program was used to assign the elevations (derived from TCalcX) to the vector TIN vertex points ? :scratchch

Also, which FS utility program was used to create the CVX vector BGLs attached above ?

This is an interesting test of concept as a workflow to create a "fictional island" via CVX vector BGLs. ;)

However, this ~10 Kilometer square surface area could also prove rather laborious to implement as a 'gridded' terrain re-meshing BGL via the CVX methods, and would less likely be efficient for performance when ultimately rendered in FS at run time than a true gridded terrain mesh made via SDK Resample.

I would suggest that as an alternative, you de-compile the CVX vector BGL "sloped flatten" (exported as a Geo-rectified object by MCX), using CvxExtractor by Patrick Germain, with output to a ESRI SHP file.


The resulting SHP file can be imported to either the Global Mapper or QGIS GIS application, then exported as a Raster DEM or DTM GeoTIFF.

The resulting GeoTIFF can be processed with a very simple INF file by SDK Resample to create a standard FS terrain mesh BGL.

The resulting true gridded terrain mesh made via SDK Resample with multi-LOD displacement data for terrain quads and Area Points will likely be more efficient for performance when ultimately rendered in FS at run time than a non-gridded single LOD CVX vector 're-meshing' BGL.

The surrounding hydro poly elevations will effectively "force" all pits and spikes in offshore water areas to 0 meters MSL ...if that elevation is assigned to those CVX vector hydro polys.

One might then be better able to use your data set with minor modifications of the other attached CVX vector BGLs to create the island.

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Hi Gary,

Where did you get the original terrain source data, and which 3D modeling or FS utility program was used to assign the elevations (derived from TCalcX) to the vector TIN vertex points ? :scratchch
Height map for fictional island generated in Wilbur (see the Fun with Wilbur tutorials at http://www.fracterra.com/wilbur.html). I geo-referenced both the exported Wilbur height map and texture PNG file in QGIS (using EPSG:4326 as the CRS) and exported as geotiff, then used gdalinfo to get center coordinates and extents. Then I created a mesh plane in Gmax to the appropriate dimensions, added a height map modifier using the Wilbur height map file and tessellated the mesh plane around the areas with larger elevation changes. Then exported the MDL from Gmax.

For the hydro polys I import the texture geotiff and import to SbuilderX. I imported the stock hydro polys using cvxExtractor and then cut a hole using the imported texture as a reference, plus an exclude for the stock hydro polys.

I've also tried directly exporting 3D models from Wilbur. I didn't have much luck with its OBJ exporter but I could export DXF quads and convert that to OBJ (using Open3DMod), then import the OBJ file into Gmax. That works well but it doesn't tessellate the mesh so you end up with a lot of polygons.

Mainly I'm just curious to see results of working with sloped flatten files generated from the Wilbur height map. I know how to use resample to get a DEM file instead. I have some other tools I can use to generate flatten files from a height map and I'll give terrain sculptor a go, but was curious to see how the MCX feature worked. Really just playing with different workflows, I also want to try the apron-to-scasm feature of MCX to make a runway surface on a sloped terrain (after previously experimenting with using attach tool to make platforms in Gmax).

I really need to start working with Blender as it has some terrain tools, but I'm still stuck on Gmax as I'm very comfortable with it.