On 19.12.2010 18:17, WanMil wrote:
Felix,
there is nothing to check. The flood blocker works only in multipolygon mode. It is not possible to implement that for the polygon mode.
Where do you think is the advantage of the polygon mode?
WanMil The advantage is:
a) Speed (if you use --transparent and then gmt to set the transparency to no) you can have for land one polygon (only land area) for sea one polygon (only sea area) and NO background polygon. b) overlapping maps - using --transparent there is less chance that a land polygon from one map, overlaps sea from another map (on GPS as only there can be several maps active at the same time).
--- in principal there is no speed advantage - but only as long as one does not attribute a color to 0x4b, however as one colors the background/land to be say white, it is much quicker to have white land background only, otherwise the GPS has to read much more data, and on older generation GPS when panning the map, there is a notable speed difference on top of flahing up background color, until it is overdrawn by the real landuse/natural/... polygon.
I don't want to put into question your final observation (polygon renders quicker on GPS device) but I cannot follow your arguments. Let's try to sort it out. Please correct me at any point if I am wrong.
I have added a picture for both sea generation methods. It shows the resulting tile and all polygons contained in the tile.
* First of all the new mp code in the coast branch generates land polygons. This is a new feature. So land+sea polygons=tile. * The polygon code creates one sea polygon covering the whole tile and adds all land polygons. The style implementor must ensure that land is drawn over sea. Otherwise the tile is flooded. * For tiles that don't contain any see one land polygon covering the whole tile is created (both for polygon and multipolygon processing).
=> a): For both variants you don't need a background polygon. The whole tile is covered by sea or land. => b): I don't understand where there should be the difference between polygon and multipolygon processing. => in principal: Do you mean that you don't want to paint land polygons but instead the background polygon? Ok, but in this case you can ignore the land polygon in the multipolgon variant but not in the polygon variant. Otherwise the background is painted and after that the sea is painted over it and you get flooded tiles. So you need to color the land polygons.
The multipolygon processing generates much more complex polygons. I think that's the reason why it is rendered more slowly on GPS devices.
WanMil I have not checked the speed after the change on GPS. I'll do that and then report back. Before definitely the quickest was --transparent and --polygons. (as I set the opqaque switch with gmaptool afterwards, I of course colored the land polygon - but the maps had no background polygon at all).