[mkgmap-dev] Gaps in surfaces

Fri Oct 6 16:15:20 BST 2023

Hi Gerd

My change to toMapUnit should be almost undetectable. Imagining mapUnits [x] as degrees over the
real range -2.5 .. +2.5, the original implementation resulted in:

-2.5 <  [-2] <= -1.5 <  [-1] <= -0.5 <  [0] <  -0.5 <= [1] <  +1.5 <= [2] <  +2.5

I've changed it to give:

-2.5 <= [-2] <  -1.5 <- [-1] <  -0.5 <= [0] <  -0.5 <= [1] <  +1.5 <= [2] <  +2.5

The change to highPrecCoord is so that 64 highPrecCoords are exactly within the appropriate
mapUnit, with deltas of -31..+32 according to the existing delta calculations.

Ticker

On Fri, 2023-10-06 at 14:34 +0000, Gerd Petermann wrote:
> Hi Ticker,
> 
> your patch rounds the problematic point to a different position, the same that is assigned to
> the new Coord instance that is derived from the cutOutInnerPolygons() method
> which involves singularAreaToPoints() and thus another place where rounding happens:
>                         int latHp = (int)Math.round(res[1] * (1<<Coord.DELTA_SHIFT));
>                         int lonHp = (int)Math.round(res[0] * (1<<Coord.DELTA_SHIFT));
> 
> I think we have to check all nodes which are part of an inner and change position because of
> your different rounding method, right? I wouldn't be surprised to find cases where a gap
> occurs
> with (just) your patch. I'll try to find an example...
> If I can't we may just use your patch, although it's much harder to understand compared to the
> original code.
> 
> Gerd