I think I now have it sorted. At least this works.
You will need to add the following two tags to the config.txt file of any region asset where you want to use the standard baseboard grid and not the "overgrown lawn" that will appear instead.
default-texture <kuid of texture to be used as grid>
trainz-build 4.8
Obviously, you substitute in the actual kuid of a real (PBR) texture grid - the one used in TRS19 is
<kuid:-25:1180> which will have to be added to the
kuid-table as well. The default-texture tag is only valid in region assets with a Trainz build number of 4.8 and above so the trainz-build tag must be included as well and set to 4.8 (at least).
In experimenting on this I used the built-in Australia region. Once you modify this region asset to include the above changes and then submit it to CM you will get two errors. There is a tag in the file, "asset-filename" (about halfway down) that should not be there - I don't know what it does, I suspect a typing error. Delete it. The second error is the missing thumbnail - a built-in asset can get away without one but a modified asset cannot.
Code:
thumbnails
{
default
{
image "thumbnail.jpg"
width 240
height 180
}
}
I will upload my modified Australia region asset to the DLS. It has the fixes (the normal TRS19 grid) and a thumbnail.
Peter