quantized mesh generator help

[Ziya Usta]

We are trying to develop pur own quantized mesh generator and visualize these terrain tiles on CesiumJS. As an input we use SRTM data that belongs to north parth of TURKEY. We generate contours on DEM, extract points from contours and triangulate points using Delanuay algorithm. Finally we tile data according to TMS specification and encode data to terrain files. When we attemp to visualize these terrain files on CesiumJS, we receive some errors. We tile data for zoom levels between 10 and 16 because our region is relatively small compared to world. But while we are zoom in to our region cesium requires tiles that are not in our zoom range and after a while when we keep zoom in everything disappears. We couldn't figure it out why this happens. Here is some pictures describe situation before and after a zoom. Any help would be appreciated.

Before some zoom

After one more zoom

[Gabby Getz]

Hi Ziya,

Do you define every tile at every level? In order to display terrain data in Cesium, the tiles must be defined for every tile at every level.

If you need some base terrain to process your DEM's, you can take a look at Cesium ion for processing and hosting your terrain data.

Thanks,

Gabby

[Ziya Usta]

yes we define every tile for every level. I am adding our own data set. Could you look at it ? It would be very helpful for us Here is the link

https://drive.google.com/file/d/1AtxjFz7MTSc7DfgiY3jOQyg-0s_jdzK8/view?usp=sharing

17 Temmuz 2018 Salı 00:24:12 UTC+3 tarihinde Gabby Getz yazdı:

[Manuel Massing]

Hi Ziya,

sounds like a culling problem, maybe this has something
to do with the horizon culling calculations?

AFAIR the occlusion point can be a bit tricky to implement.

Manuel

Am 25.07.2018 um 12:03 schrieb Ziya Usta:
> yes we define every tile for every level. I am adding our own data set.
> Could you look at it ? It would be very helpful for us Here is the link
>
> https://drive.google.com/file/d/1AtxjFz7MTSc7DfgiY3jOQyg-0s_jdzK8/view?usp=sharing
>
> 17 Temmuz 2018 Salı 00:24:12 UTC+3 tarihinde Gabby Getz yazdı:
>
> Hi Ziya,
>
> Do you define every tile at every level? In order to display terrain
> data in Cesium, the tiles must be defined for every tile at every level.
>
> If you need some base terrain to process your DEM's, you can take a
> look at Cesium ion for processing and hosting your terrain data

> <https://cesium.com/docs/tutorials/getting-started/>.

>
> Thanks,
> Gabby
>
> On Tuesday, July 10, 2018 at 12:07:34 PM UTC-4, Ziya Usta wrote:
>

> *We are trying to develop pur own quantized mesh generator and

> visualize these terrain tiles on CesiumJS. As an input we use
> SRTM data that belongs to north parth of TURKEY. We generate
> contours on DEM, extract points from contours and triangulate
> points using Delanuay algorithm. Finally we tile data according
> to TMS specification and encode data to terrain files. When we
> attemp to visualize these terrain files on CesiumJS, we receive
> some errors. We tile data for zoom levels between 10 and 16
> because our region is relatively small compared to world. But
> while we are zoom in to our region cesium requires tiles that
> are not in our zoom range and after a while when we keep zoom in
> everything disappears. We couldn't figure it out why this
> happens. Here is some pictures describe situation before and

> after a zoom. Any help would be appreciated.*
>
>
> Before some zoom
>
>
> <https://lh3.googleusercontent.com/-NhcmMD7mQyw/W0TZWkOJu4I/AAAAAAAAAp0/wuUcoWw0etoP7Z7wQgA3HPUW5lXWkqzvgCLcBGAs/s1600/sandcastle1.png>
>
> After one more zoom
>
> <https://lh3.googleusercontent.com/-7tPsCgu17ks/W0TZrFOgngI/AAAAAAAAAp8/2inZ8ELR9XogogIJQrq75AhBpSl-oTptQCLcBGAs/s1600/sandcastle2.png>
>
>
>
>
> *
> *
>
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[Gabby Getz]

Yes, as Manuel suggests, this is most likely a culling problem. Quantized-mesh tiles contain a horizon culling point which determines when the camera culls a tile. I would suggest using Cesium ion to process your terrain data, see my link above.

Thanks!

Gabby

> an email to cesium-dev+unsubscribe@googlegroups.com
> <mailto:cesium-dev+unsub...@googlegroups.com>.

[bilon...@gmail.com]

We recently open sourced C++ tool which is basically quantized-mesh generator https://github.com/heremaps/tin-terrain
It takes into account horizon occlusion point and it seems to work correct.

We also have example of rendering output tiles in Cesium.js https://github.com/heremaps/quantized-mesh-viewer
Note that we solved problem with missing tiles on a frontend rather then generating empty tiles;