During my first attempt I noticed a message about nodata values:
gdalwarp -of TERRAGEN -co MINUSERPIXELVALUE=20 -co MAXUSERPIXELVALUE=1347 "src.tif" "dest.ter" Creating output file that is 8743P x 6159L. Processing input file src.tif Using internal nodata values (eg. -3.40282e+038) for image src.tif 0...10...20...30...40...50...60...70...80...90...100 - done.
(GDAL 1.7.0b2, FWTools 2.4.7, released 2010/01/19)
However, after the conversion I opened up the file in Terragen and while no errors were presented, the file contained no terrain data. I proceeded to open the file in a hex editor and noticed that while a proper file header appears to be present, the majority of the data is a bunch of zeros. If I understand the Terragen format correctly, it appears either no "chunks" are present or they all contain values of zero.
This is in stark contrast to performing a conversion within Terragen itself - I can import the
src.tif file in Terragen and export a
.ter file. The terrain is present in all its glory within Terragen. Viewing this file in a hex editor I can see many "chunks" of non-zero data present throughout the file.
Strangely, the file generated by gdalwarp is roughly the same file size as the one generated by Terragen, again the difference being it is full of zeros.
$ gdal_translate -of TERRAGEN -co MINUSERPIXELVALUE=-4.452 -co MAXUSERPIXELVALUE=3052.968 src.tif dest.ter Input file size is 8743, 6159 0...10...20...30...40...50...60...70...80...90...100 - done.
I even tried specifying "none" for the nodata value:
$ gdal_translate -of TERRAGEN -a_nodata none -co MINUSERPIXELVALUE=-4.452 -co MAXUSERPIXELVALUE=3052.968 src.tif dest.ter Input file size is 8743, 6159 0...10...20...30...40...50...60...70...80...90...100 - done.
(GDAL 1.10.0, released 2013/04/24)
However, in each case the result was the same. The terragen output file was chock full of zeros. I suspect that I need to provide additional parameters to the gdal tools in order to properly convert the data to the terragen format. I'm just not sure where to start. Any ideas?
For reference, gdalinfo outputs:
I have both full output from
gdalinfo -hist and brief output from:
gdalinfo -nomd -norat -noct -nofl
I have also run the same query on the file that was converted by Terragen itself, the one that contains proper terrain data.