Quantized mesh format: how accurate the tile s bSphere needs to be

CesiumJS
1

Hello,

I have a simple conceputal question. In your description of the quantized mesh format, one needs to know the bounding sphere of a tile. After a little research, I realize that algorithms calculating exact bounding spheres are quite complex and demanding.

I found much simpler algorithms but their accuracy is variable. Between 5 and 20% bigger than the optimum. I realize that all that might be resolution dependent, but how accurate do we need to be?

Thank you for your anwsers.

Kind Regards
LG

2

The bounding sphere you supply must contain all the vertices, but being bigger than optimal won’t break anything, other than rendering some extra tiles unnecessarily. Cesium has code to compute a bounding sphere from vertices in the BoundingSphere class.

Kevin

3

Hi thanks fo the reply, all I needed to know for now.

4

Hi, I’ve implemented a tool to convert folders of ASC and other DTMs to quantized-mesh format.
I’ve used Miniball to calculate the minimum bounding sphere (http://software.icecube.wisc.edu/icerec_trunk/doxygen/phys-services/Miniball_8h_source.html)

The results obtained are more than satisfactory.

Here is a screenshot: http://www.daigio.it/qmeshsample.png

Davide