Validator - Bounding Volume Spatial Coherence

For CesiumGS/3d-tiles-tools#9 @sumitshyamsukha

Let’s do this one now:

tile.content.boundingVolume, when defined, is completely inside tile.boundingVolume (use Cesium’s functions)

There are three bounding volume types: region, box, and sphere. They are defined here: https://github.com/AnalyticalGraphicsInc/3d-tiles/blob/master/schema/boundingVolume.schema.json

If a tile has a content bounding volume, check that it is inside it’s bounding volume. To visualize what a bounding volume / content bounding volume looks like, go to the 3D Tiles Sandcastle when running the 3d-tiles branch in Cesium and check out the BV On/Off and Contents BV On/Off buttons.

We’ll need support the following checks:

• Region inside region
• Box inside region
• Sphere inside region
• Sphere inside sphere
• Region inside sphere
• Box inside sphere
• Box inside box
• Region inside box
• Sphere inside box

I’ll update with ideas for solving some of these, but to start region inside region should be pretty straightforward. Just need to check that the west/south/east/north/min/max are within the other’s values.

[lilleyse]

Yes add it to the existing traversal in validateTileset.

[lilleyse]

@rms13

Let’s tackle the region tests now.

• Box inside region
• Sphere inside region
• Region inside sphere
• Region inside box

While region is technically a curved surface along the earth, I think we can assume for most cases that it is close enough to a box shape. This will heavily simplify these 4 checks.

To convert a region to a box, check out TileBoundingRegion in Cesium, specifically:

OrientedBoundingBox.fromRectangle(this.rectangle, this.minimumHeight, this.maximumHeight, ellipsoid);

Once converted to a box the previous written comparisons can be used.