[Qgis-user] 16 bit greyscale map gives stepping artifacts

[wout zweers]

Hi all,


Maybe someone can help me further with the following item:


*how to avoid banding in a greyscale height map *


I make detailed maquettes with a 3d printer. The model, a detailed 3D 
mesh, will be generated in ZBrush. 8 bit greyscale maps are not detailed 
enough, I need at least a 16 bit map to avoid stepping (banding).

My basic maps are 32 bit geotiff (Netherlands  AHN, downloaded directly 
from the AHN Server. I make a layer with this map and then process it:

I use the processing toolbox: GDAL > raster conversion > translate. 
Settings: output data type = UInt16a

This should do the job, it produces a 16 bit greyscale map that i can 
store as a tiff or png, but when i use this in ZBrush I notice (typical) 
8 bit-like banding. ZBrush is capable of processing 16 bit greyscale 
maps. In Qgis I could see the banding in the resulting map as well.

I tried other output formats (float32, Int16) but they did not work either.

Maybe scaling is necessary (0-255 to 0- 65535) or setting a no data 
value (65535? 0?) If so, what are the correct settings? I kept tinkering 
with it, but did not find the proper setting or procedure


Is there anybody who has the same problem, or perhaps solved it already? 
It would be very convenient to know how to do it, the work arounds are 
very labour intensive.


Wout Zweers, Netherlands
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