CellID lost when S2RegionCoverer.getCovering() about s2-geometry-library-java HOT 6 CLOSED

You might display the bounds of each cellId, instead of it's center point. I think you'll see that there are various cell sizes (levels). You can avoid this feature - if you want to - by specifying the min/max cell levels that the S2RegionCoverer is allowed to return.

from s2-geometry-library-java.

@lokkju Thanks for reply!
I do want to keep one same level within the circle area and have set the min/max levels to be same, but it seems that it will still automatically replace four child cells with their parent as annotated by author for getCovering().

/**

• Return a normalized cell union that covers the given region and satisfies
• the restrictions EXCEPT for min_level() and level_mod(). These criteria
• cannot be satisfied using a cell union because cell unions are
• automatically normalized by replacing four child cells with their parent
• whenever possible. (Note that the list of cell ids passed to the cell union
• constructor does in fact satisfy all the given restrictions.)
  */
  public S2CellUnion getCovering(S2Region region) {
  S2CellUnion covering = new S2CellUnion();
  getCovering(region, covering);
  return covering;
  }

Is there any alternatives to avoid this feature?

from s2-geometry-library-java.

you might try:

1. getSimpleCovering
2. loop through the S2CellUnion and emit children elements for any parent element above your desired level
3. use reflection to call getCoveringInternal and get the raw S2CellIds
4. a custom S2CellUnion that doesn't normalize the results (this code isn't at all tested, just gives you an idea):

public strictfp class S2CellUnionDenormalized extends S2CellUnion {
  public void initSwap(ArrayList<S2CellId> cellIds) {
    initRawSwap(cellIds);
    // skip normalization
    // normalize();
  }
}
S2CellUnionDenormalized s2cud = new S2CellUnionDenormalized();
regionCoverer.getCovering(region, s2cud)

I'd probably suggest (1) or (2) as the best options.

from s2-geometry-library-java.

@lokkju Get it. Appreciate for your help!

from s2-geometry-library-java.

I'd suggest #5: use denormalize, to get the cells at the particular cell level you want.

from s2-geometry-library-java.

(Feel free to reopen if that doesn't work well for you)

from s2-geometry-library-java.