fix (3dtiles): fix SSE computation

[NikoSaul]

Use distance to bounding volume instead of distance to center of the bounding volume
Issue: #185

[nguyenign]

It seems to me that it continues to download all the tiles!

[NikoSaul]

Can you give me your tileset.json please?
Else this PR doesn't fix all problems for the issue #185 but just the sse.

[nguyenign]

you can find the download link in this issue, but if it's not enough i can send you a bigger 3dtiles.

[Jeremy-Gaillard]

Your problem isn't really a bug. We tried making your tileset work and we identified two issues:

• Missing refine: "ADD fields in some of the tiles
• The SSE refinement threshold is much higher in Cesium (16 by default, compared to 1 in iTowns)

So it works properly, it's just that the building disappear only when you're very far away.

We will make a PR to change the SSE threshold and make it customisable.

[nguyenign]

• We need to define only one time refine, then it's optional!

"The refine property is a string that is either "REPLACE" for replacement refinement or "ADD" for additive refinement. It is required for the root tile of a tileset; it is optional for all other tiles. When refine is omitted, it is inherited from the parent tile."

• i think we should use dynamic sse as the link i sent you in chat.

can you please commit your modif?

[autra]

LGTM Thanks!

[Jeremy-Gaillard]

We need to define only one time refine, then it's optional!

My bad, I'll add it to the list of thing to fix.

[nguyenign]

ok jeremy but do attention, refine is not fixed, we can have many small 3dtiles in a big 3dtiles with which use different refine method.