Mesh "terracing"

I'm getting the terracing effect that the SDK talked about in my terrain mesh that I've created. I've toyed with the FractionBits value, anything over 6 causes wild undesirable effects. Not sure about BaseValue, it doesn't appear to do anything... the airport elevation is at 2653 ft. / 808.7 m if that makes any difference. It's on a hill surrounded by a valley and higher mountains.
Hi Jon:

Was the original data source GIS file format 32-Bit GeoTIFF ?

If so, was a 32-bit floating point elevation grid format specified in Global Mapper during your GeoTIFF output ?

A 32-bit floating point ex: GeoTIFF source file is required for successful use of FractionBits to eliminate contour 'terracing', :pushpin:

BTW: IMHO, you may not need more than a *.INF FractionBits parameter value of "2" or "3" for this project location

FYI: Global Mapper (aka "GM") will initially load source files in their native GIS cartographic "projection"; this typically will be a 'non-warped' map format such as in your source file above.

After all your NED elevation source files are all loaded in Global Mapper in the 'non-warped' map format of their native GIS cartographic "projection", one should export a Elevation Grid format GeoTIFF Raster file.

Next, after unloading all files, one loads the 1-piece Elevation Grid format GeoTIFF Raster file.

Then one must re-project that 1-piece Elevation Grid format GeoTIFF Raster file into:

Geographic (Lat-Lon) projection / WGS84 datum / Units in Arc Degrees (aka "EPSG: 4326")


An important consideration may be necessary when working with Global Mapper due to a change in behavior which was apparently implemented in more recent versions in that program. :pushpin:

It seems that Global Mapper (sometimes) dynamically accepts and defaults to the internal projection settings of a GIS data file in order to import it and display it within the Global Mapper workspace ...even if one has already set the default configuration of Global Mapper to be at "Projection: "Geographic (Latitude / Longitude)", Datum: "WGS84", Planar Units: "ARC DEGREES". :alert:

So when one opens a GIS data file, it may by default be displayed in the same internal projection stored within that file.

To "force" the re-projection in Global Mapper to make the GIS source data display and export in the format required when that data is to be exported for use with the FS SDK, one must again reset the projection during the work session immediately after one's first GIS data file is loaded ...via this procedure:

The correct configuration to set up in Global Mapper before opening a GIS data file or downloading GIS data ...and AGAIN 'after' opening data files when that data is to be "Exported" for use with the FS SDK:

Global Mapper Menu > Tools > Configure... > [Projection Tab]

Projection: "Geographic (Latitude / Longitude)"

Datum: "WGS84"

Planar Units: "ARC DEGREES"



Value: "0"

BTW: As a visual clue that one has 'remembered" to re-project to WGS84 for ex: FS SDK use, the Global Mapper workspace display of the GIS data should compress vertically and rotate counter-clockwise to some extent. ;)

NOTE: Global Mapper is IMHO likely to yield more consistent results when the GIS file which one needs to re-project is the ONLY file loaded in a particular work session; thus it is preferable to not attempt to use that file as one of multiple files which are being turned on and off in the "Control Center" within a work session.

If it is necessary to attempt isolation of a particular GIS file which one needs to re-project and/or export as the ONLY "active" or visible file within a multiple file layer work session, it may be likely to yield more consistent results when that GIS file is loaded FIRST, re-projected, and then load the other multiple file layers afterwards. :pushpin:

Example settings in Global Mapper for export of elevation data

This configuration may work for certain source data file formats in Global Mapper after downloading and opening a GIS elevation data file ...when that data is to be exported for use with FS SDK Resample to output a terrain mesh BGL:

1.) Global Mapper Menu > File > Export > Export Elevation Grid Format...

2.) At 'Select Export Format' prompt, choose "GeoTIFF" from the pick list

3.) In 'GeoTIFF Export dialog, on [GeoTIFF options] tab:

File Type: "Elevation 32-bit floating point samples (=Radio Button 'Ticked')

Vertical Units: "Meters"

Resampling: "Bicubic Interpolation"

Sample Spacing / Scale: (disregard =Automatically filled in by Global Mapper)

Always Generate Square Pixels: (=Checked)

Always Export At The Fixed Scale 1: "0" (=Not-Checked)

DPI Value To Save in Image (0 for None): "0" (=Not-Checked)

Compression: Default (No Compression)

ADVANCED: Use Tile Rather than Strip Orientation: (=Not-Checked)

ADVANCED: JPEG-in-TIFF Quality: "75" (disregard =Automatically filled in by Global Mapper)

Interpolate to Fill Small Gaps in Data: (=Checked)

Generate TFW (World) File: (=Checked)

Generate PRJ File: (=Checked)

Generate OziExplorer .map File: (=Not-Checked)

ADVANCED: Don't Write GeoTIFF Header: (=Not-Checked)

4.) In 'GeoTIFF Export dialog, on [Tiling] tab:

No Tiling - Just One Export File: (=Radio Button 'Ticked')

Skip Existing Files (Use to Complete Cancelled Exports): (=Not-Checked)

5.) In 'GeoTIFF Export dialog, on [Export Bounds] tab:

All Loaded Data: (=Radio Button 'Ticked')


Click "[Draw a Box...]" button and select desired area from displayed workspace (or specify otherwise via the GUI in that dialog box Tab).

You should now have a elevation GeoTiff source file compatible for use with FS SDK Resample.

The GeoTiff source file should be ready for use with a *.INF file for processing of the elevation data by FS SDK Resample to output a FS terrain mesh BGL.
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The source file, as downloaded from USGS was actually a .img file. I just exported it as a 32-bit floating point GeoTIFF as specified above, attempted to resample it and it gave me the "Only geographic coordinates are supported" line. I'm missing something.

You'll pardon me as I'm somewhat new to messing with mesh!

Seeing someone have fun with a break-through in their FS Development can make ones efforts all worthwhile sometimes ! :)


'Most' data available from USGS requires re-projection in Global Mapper from its original native non-warped projection to:

"Geographic (Latitude / Longitude)", Datum: "WGS84", Planar Units: "ARC DEGREES"

...which is the "warped" GIS data file format required for compatible use with SDK Resample. ;)

"Warped" GIS data in terrain BGLs is then "warped" to fit variable FS terrain QMID grid quad vertex point positions at run time :pushpin:

Happy scenery building ! :santahat:

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