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

Syd Visser sydv at sjgeophysics.com
Thu Dec 14 12:48:31 PST 2017


As a geologist and geophysicist it is extremely important for us to be 
able to see below topography and inside (slice and dice) volumes as in 
NVIZ in grass.

I have always thought that only being able to view topography form the 
top or volumes form the outside not inside was called 2.5D.

I am wandering if you should differentiate between them.

it would be extremely useful for us to ab able to render 3D raster from 
grass. Basically the same as in NVIZ of Paraview



*Syd (Sipke) Visser, P.Geo.*
President, Snr. Geophysicist/Geologist

Tel: 1 (604) 582-1100
Cell: 1 (604) 813-1440
sydv at sjgeophysics.com
www.sjgeophysics.com <http://www.sjgeophysics.com>


On 2017-12-14 02:41 AM, 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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