Eisenbahn-Bildschirmschoner-Wiki

[BT :<X>,<Y>, <W>,<H> ]
[BT :<X1>,<Y1>,<W1>,<H1>,<X2>,<Y2>,<W2>,<H2>, … ]

Block Transparent

A rectangular field is made transparent

Using this modifier you can mask out loads on open freight cars or exhaust on steam engines. It is possible to define the parameters <X>, <Y>, <W>, <H> more than once, thereby creating multiple transparent rectangular areas.  This is a simpler method than using multiple [BT: ] commands.