[QGIS-Developer] QGIS 3D: looking below the terrain model

[Andreas Neumann]

Hi Martin, 

Thanks a lot for your reply. 

I would be fine if both of these wouldn't be defaults but configurable. 

Thanks, 

Andreas 

On 2017-12-14 11:41, Martin Dobias wrote:

> Hi Andreas
> 
> On Wed, Dec 13, 2017 at 3:31 PM, Andreas Neumann <a.neumann at carto.net> wrote: 
> 
>> Hi,
>> 
>> Being a caver, I have a lot of underground data. Thanks to the support from
>> Martin I got them to load correctly as 3D polygondata.
>> 
>> However, one issue I have is that the terrain rendering disappears when I
>> look below the terrain model surface - which isn't so nice for a caver or
>> geologist. Is this also an issue about culling? Would it be possible to
>> enable the rendering of the backside of the terrain surface?
> 
> The fact that terrain from below is not rendered is a very common
> optimization in 3D rendering called back-face culling - it makes
> rendering faster by only rendering triangles that are facing camera.
> It is not difficult to turn it off, but I am not sure if the culling
> should be turned off by default...
> 
>> The other issue I have is that tilting is somehow locked at the horizon. I
>> can look down on the terrain and then rotate the whole model until I look
>> sideway into the model, but than the rotation is blocked. I cannot rotate
>> any further so that my camera gets below the surface and that I could move
>> below the surface and look up towards the terrain. I guess this makes a lot
>> of sense for people who do not need to explore things below the terrain
>> surface, but for geologists or cavers, it would be great if this
>> rotation/tilting blocking could be disabled somehow.
> 
> Yes this is intentionally locked (for now) as most users would
> probably complain if the camera went below the horizon. I understand
> you use case though - maybe we can have a underground/caver/geologist
> mode for the 3D view that would both disable back-side culling of
> terrain and also unlock camera rotation...
> 
> Cheers
> Martin
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