Hillshade Layer Style wrong if OpenCL acceleration is enabled

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Author Name: luca bellani (luca bellani)
Original Redmine Issue: 21121
Affected QGIS version: 3.5(master)
Redmine category:rasters
Assignee: Alessandro Pasotti

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Hello. I noticed that with certain DEM (not all), QGIS 3.4.4 generates a display problem in the "hillshade" style.
Only in the layer style, because the GDAL geo-process works perfectly.

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• 2.PNG (luca bellani)
• dem_prueba.tif (luca bellani)
• comparacion.png (luca bellani)
• DEM_prova2.rar (luca bellani)
• 1.PNG (luca bellani)
• 3.PNG (luca bellani)

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Author Name: luca bellani (luca bellani)

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• 14193 was configured as dem_prueba.tif

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• dem_prueba.tif (luca bellani) - dem

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Author Name: Alessandro Pasotti (@elpaso)

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I think it's a know issue and there is not much we can do, did you try to adjust the "Resampling" parameters in the renderer configuration?

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• status_id was changed from Open to Feedback
• assigned_to_id was configured as Alessandro Pasotti
• operating_system was changed from Windows 10 64 bit v. 1809 to Any
• priority_id was changed from High to Normal
• version was changed from 3.4.4 to 3.5(master)

[qgib]

Author Name: luca bellani (luca bellani)

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Salve. What is strange to me, is that in QGIS 2.18 it does not give any problem.
And it seems to be something random. In QGIS 3.4.4, I loaded the DEM again, and adjust the "Resampling" parameters "bilineal", and now all is ok.

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Author Name: Alessandro Pasotti (@elpaso)

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I think it depends on the zoom level too.

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Author Name: Giovanni Manghi (@gioman)

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Alessandro Pasotti wrote:

I think it's a know issue and there is not much we can do, did you try to adjust the "Resampling" parameters in the renderer configuration?

closing then?

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Author Name: luca bellani (luca bellani)

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I have reviewed other DEMs that gave me problems, and as can be seen in the comparative image, the problem is presented in QGIS 3, not in QGIS 2. I have already completely manipulated the resampling options, but it is not solved.
It's funny that it's a bug, but only in the new version of QGIS.
Annex also another DEM, so that they can prove it.
Thanks for the support.

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• 14212 was configured as comparacion.png
• 14213 was configured as DEM_prova2.rar

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• comparacion.png (luca bellani) - imagen comparativa QGIS 2 & 3
• DEM_prova2.rar (luca bellani) - Dem de prueba

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Author Name: Alessandro Pasotti (@elpaso)

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Out of curiosity: are you using OpenCL acceleration? If yes can you try to disable it?

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Author Name: luca bellani (luca bellani)

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Yes! That's the reason!
Deactivating OpenGl and always putting the resampling in "bilinear" is displayed correctly.
Thank you!

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• subject was changed from Error Hillshade Layer Style to Hillshade Layer Style wrong if OpenCL acceleration is enabled
• status_id was changed from Feedback to Open
• operating_system was changed from Any to

[qgib]

Author Name: Alessandro Pasotti (@elpaso)

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Luca, can you please make a quick test with OpenCL activated and tell me if it works with the sampling bilinear option or if it does not?
If it does not work, can you please have a look to the QGIS messages (small icon at the bottom right) in the OpenCL section?
Also, please paste a picture of the OpenCL tab in your settings or copy-paste the information about your OpenCL device.

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Author Name: luca bellani (luca bellani)

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I did the tests. When you activate OpenCl, even if you change the type of resampling, it is displayed incorrectly.
In the message window, I do not see the OpenCl tab, I do not know if I have something wrong installed. Annex images.
Thank you

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• 14229 was configured as 1.PNG
• 14230 was configured as 3.PNG

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• 1.PNG (luca bellani) - opencl tab
• 3.PNG (luca bellani) - bilineal hillshade style wrong

[qgib]

Author Name: Alessandro Pasotti (@elpaso)

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PR #9070

I'd like you to test if this patch solves your issue (with OpenCL ativated).

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• status_id was changed from Open to In Progress
• category_id was changed from Symbology to Rasters
• pull_request_patch_supplied was changed from 0 to 1

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Author Name: Alessandro Pasotti (@elpaso)

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Applied in changeset 1aef9cf.

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• status_id was changed from In Progress to Closed
• done_ratio was changed from 0 to 100