[QGIS-Developer] QGIS 3D: Fails with large DTM image

[Martin Dobias]

Hi Calvin

I have tested with your layer and the problem is with the no-data
values - right now the terrain generator does not have a concept of
no-data values so they are interpreted as valid values, which in this
case is a very high number (around 1e38) and that breaks the 3D view.
Best to keep an eye on https://issues.qgis.org/issues/17558 as that is
essentially the same problem. As a temporary workaround, you could try
to change your layer's no-data values closer to the valid range (e.g.
zero or 500).

Cheers
Martin


On Fri, Dec 15, 2017 at 10:51 PM, C Hamilton <adenaculture at gmail.com> wrote:
> The current DEM that I am working with is located here:
>
> http://gis3.oit.ohio.gov/ZIPARCHIVES/ELEVATION/GRIDMOSAICS/GRE_DEM_MOS.zip
>
> I'm surprised that resizing did not help so I am not sure what is wrong. I
> created a small 560x460 image that I have attached. It does not work for me.
>
> Thanks,
> Calvin
>
> On Fri, Dec 15, 2017 at 4:22 PM, Martin Dobias <wonder.sk at gmail.com> wrote:
>>
>> Hi Calvin
>>
>> Could you please point me to such a DEM to try it out myself? Or even
>> better, file a ticket on issues.qgis.org so that we do not forget
>> about it. Not sure from the top of my head what could go wrong there -
>> the raster size should not be the reason really as the raster data
>> access is using the same code paths as 2D rendering would. Maybe there
>> is something in the data that causes the problem. If you resize the
>> large DEM to e.g. 5000x5000 pixels, does that help?
>>
>> Regards
>> Martin
>>
>>
>> On Fri, Dec 15, 2017 at 8:38 PM, C Hamilton <adenaculture at gmail.com>
>> wrote:
>> > QGIS 3D has a lot of potential and works well with small DEM data sets,
>> > but
>> > when ever I try it with a large DTM image I just get a white screen. I
>> > tend
>> > to work with large DEMs (50000 x 50000 pixels and larger) and I would
>> > love
>> > for this to work with it properly.
>> >
>> > Do you have any ideas why this is the case? I have tried this with an
>> > AIG/Arc/Info Binary Grid image as well as a GeoTIFF with overviews.
>> >
>> > OS: Windows 7; QGIS 3 Version: 2.99.0-238
>> >
>> > Thanks,
>> >
>> > Calvin
>> >
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