feat(ImplicitTiling): add octree support

[AnthonyGlt]

Add octree support for implicitTiling.

TODO:

• add a method to get directly the type of subdivision or use getBoundsDivider ?
• test on region octree tileset. I don't have a tileset to try on

[AnthonyGlt]

@gkjohnson
Is there really a thing to add in the case of a box ?

3DTilesRendererJS/src/base/plugins/SUBTREELoader.js

Lines 773 to 774 in 727a440

	// Iterate over the three obb axes. Skip the z axis since octree
	// implicit bounds are not supported.

Indeed, it looks like the box is not subdvided:

(example 3d-tiles-samples/1.1/SparseImplicitOctree/tileset.json )

[gkjohnson]

add a method to get directly the type of subdivision or use getBoundsDivider ?

What do you mean by this?

test on region octree tileset. I don't have a tileset to try on

Looks like 3d-tiles-samples/1.1/SparseImplicitOctree/tileset.json works for this, right?

Is there really a thing to add in the case of a box ?

The loop referenced adjusts the bounding box center and half-axes to describe the specific subdivided child. Note that the array for a bounding box is defined as 3 values for the center, and 3 values for each half-vector on each axis.

Currently the loop for adjusting the bounds does two things - it adjusts the half axes and adjusts the bounding box center by each necessary axis. Currently the loop only iterates over two axes to adjust their scale and the center because a quad tree only splits along X and Y.

So two things need to happen:

• The loop needs to iterate over all the half-width vectors (ie changing 2 to 3 when using an OCTREE split).
• And accommodate the z-axis (ie i===2) when computing the axisOffset value so the center can be offset in the z-half-width direction in addition to the x and y offsets currently applied.

Hopefully that makes sense - let me know if anything is still unclear

[AnthonyGlt]

Thank you for the answer :D

add a method to get directly the type of subdivision or use getBoundsDivider ?

What do you mean by this?

• I meant that I'm using this condition tile.__implicitRoot.implicitTiling.subdivisionScheme === 'OCTREE' , could be smarter to use an other method

The loop needs to iterate over all the half-width vectors (ie changing 2 to 3 when using an OCTREE split).

• Yes, I must have had a brainfreeze to miss that 😬

test on region octree tileset. I don't have a tileset to try on

Looks like 3d-tiles-samples/1.1/SparseImplicitOctree/tileset.json works for this, right?

It's bounding box, I'll modify it to have region then :)

[AnthonyGlt]

[gkjohnson]

I meant that I'm using this condition tile.__implicitRoot.implicitTiling.subdivisionScheme === 'OCTREE' , could be smarter to use an other method

Yeah it's a little long - maybe a function called "isOctreeSubdivision" that returns true or false would make it more readable.

Looks great! It would be nice to get parent bounds rendering at some point so we can see the full hierarchy a la #730.

[gkjohnson]

Looks like the comment above can be updated.

[gkjohnson]

Would be good to add some comments here, I think, regarding what this is adjusting and how.

[gkjohnson]

Interestingly just setting z to "0" here would make all the octtree / quadtree logic "just work" even if we don't have conditions for the two tree types 🤔. Maybe worth making a comment for later

[AnthonyGlt]

I don't think that the 0 value even matters, it could be whatever. In the case of a quadtree, the Z value is not used in any calculus and is called only at the url parsing, but there wont be a "z" coordinate in a quadtree url