[QGIS-Developer] Problems with QGIS 3 Hillshade

[Nyall Dawson]

On Sat, 9 Jun 2018 at 06:25, C Hamilton <adenaculture at gmail.com> wrote:
>
> OS: Windows 7
> QGIS 3.0.3
>
> I have encountered several issues with the Hillshade algorithm in QGIS 3.
>
> 1. It is much slower that the QGIS 2 hillshade perhaps as much as 10x slower. This is a problem because I process very large images. 60,000 x 80,000 pixels or greater. I eventually killed the process and went back to QGIS 2 to complete the job.
>
> 2. I tried using Multidirectional shading and received an error. This is basically the command issued.
>
> gdaldem hillshade input.tif output.tif -of GTiff -b 1 -z 1.0 -s 1.0 -az 315.0 -alt 45.0 -multidirectional

Can you post the command created in QGIS 2.18 for comparison?

> I get the gdal error "ERROR 6: -multidirectional and -az cannot be used together". If multidirectional is enabled then you cannot add the -az parameter. If have tried running the same command in the command line and removed the -az and it worked fine.

Confirmed, thanks - fixed by https://github.com/qgis/QGIS/pull/7209
and unit tests added.

Nyall