Edit: I was typing this before you posted, few odds and ends
I see california-grass.png has been updated. My detiled darker version was called california-grass-2.png. The darker version of the california-grass.png still exists. Was this kept for airport keep? I see California.xml was modified to use california-grass-2.png for non-airport keep grass, but cit seems California-grass.png is used for things other than airport keep in UAE.xml and mexico.xml and these should be modified too.
(I'm using a text search utility called astro-grep in windows that displays the context in the file for each search result, but in Linux there is probably builtin commandline tools or diff tools which might do that. This seems to be the easiest way to work with materials.)
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Since the new smaller 1024 structure files are used for airport keep, replacing the old version, the <overlay_layer_magnification> needs to be doubled to 16.0 for all materials with 8.0. None of them set <overlay_alpha> so the global-summer value holds.
Some materials use the old grass structure set to much larger grass size (lower <overlay_layer_magnification>). Some values were as low as 1.3. Even an 8.0 looks too big. What to do about these?
<overlay_layer_magnification> already set to 16+ is used by definitions with sand and gravel overlays, and these files are fine to leave alone: africa_desert.xml (32.0), africa_mediterranean.xml (16.0), brazil_caatinga.xml (16.0),
<overlay_layer_magnification> set to 8.0: , africa_rainforest.xml , azores.xml,brazil_amazon_forest.xml, brazil_pantanal.xml, jan_mayen.xml, mexico.xml, southeast_asia.xml,
<overlay_layer_magnification> lower than 8.0: ascension.xml (4.0),brazil_pampas.xml (4.0),corse.xml (set grain layer magnification), jan_mayen.xml (0.6),mexico.xml (set grain layer magnification), southeast_asia.xml (4.0), southern_europe.xml (set grain layer magnification), tropical_south_america.xml (set grain layer magnification), global-winter.xml (2.0)
Edit: in corse.xml, southern_europe.xml, mexico.xml, and tropical_south_america.xml: the overlay is used in the n="15" slot. So <overlay_layer_magnification> should be left untouched. <grain_layer_magnification> should be set to 16.0 or whatever.
The old grass structure was based on airport-grass2.png (
link. It's a much finer / zoomed out grass type. I think the intention was to try to large display leaf structure which the new grass has anyway. The new grass structure is more appropriate for these tropical areas.
Jan Mayan probably has more moss than grass when it has vegetation at all. So the older grass structure is more appropriate(?).
So the older grass structure file should be kept as it's probably suitable for mossy or bare airport keeps in very northern areas. If this approach is taken then the filenames need to be changed too. I think airport_grass_structure_overlay1.png and airport_grass_structure_overlay2.png is a bit more descriptive than airport_grass_overlay.png as it's unclear what type of overlay this is for newcomers.
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In azores.xml: the old green (summer) airport-grass-autumn.png is used. Probably airport-grass-summer.png is more appropriate.
The current airport-grass-autumn.png (
link) probably should be renamed airport-grass-summer2.png to avoid confusing future people - as there's no use for autumn textures.
In current global-summer.xml (
link), airport-grass-autumn.png is called in <texture>Terrain/airport-grass-autumn.png</texture>. That's normally overridden by n="13" for ALS, but maybe it's useful for some other renderers or something as definitions seem to all have a <texture> element that seem redundant. The reference should be changed to airport-grass-summer.png, or otherwise fixed.
Kind regards