[Bug/Feature Request] Set nodata value on geotiff (RGB / DSM) export

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Geotiffs exported from RealityCapture do not have the nodata value (from the geotiff spec) set correctly.

  • DSM have a value of nan for pixels which do not fall under a mesh polygon, but nodata is undefined (it should then be set to nan)
  • RGB geotiffs have an alpha band, with alpha = 0 for such pixels (rather than 255 for opaque or anything different than zero for semi-transparent pixels)

Any subsequent processing applied within standard GIS libs (gdal, qgis, saga, grass etc) therefore requires editing the nodata value via either of these:

gdal_edit -a_nodata nan geotiff.tif
gdal_calc.bat -A dsm.tiff --outfile=dsm-correct-nodata.tiff --calc="nan_to_num(A, nan=-9999)" --NoDataValue=-9999

RC should set the nodata on the geotiff metadata correctly.

Additional bug: DSM have lots of small (often 1 or 2px) holes on tiles seams (with nan value). This become even more apparent when the dsm geotiffs are tiled into COGs (Cloud Optimized Geotiffs). Hence the need to use the gdal_fill utility beforehand to fix this second RC bug.

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Thank you for noticing this, we will create a bug regarding this issue.

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