Currently I do that in 7 discret steps, Jan, Feb, ... Jun, Jul, Jun, ... Feb
It works nicely, if I increase or decrease the snow line by one. But it starts to look really ugly, if I change it by more than one height level at once. Snow line height values as in the definition of it have to be - according to the specs - be mutliples of 8. That is observed as far as I could establish (sprite #36 allows testing it, sprites #37 + #38 actually define the snow line, sprites #12 - #35 calculate it from the parameters).
I'd be glad to receive pointers what's going wrong for increases of the snow line of more than one tile height between two months.
EDIT: the relevant wiki pages as far as I know:
http://wiki.ttdpatch.net/tiki-index.php ... t_table_10_
http://wiki.ttdpatch.net/tiki-index.php ... _height_97_
http://wiki.ttdpatch.net/tiki-index.php?page=Action6
EDIT2: The remaining snow in the screenshot are not tiles which have not been visited by the tile loop....
EDIT3: attached the grf file. Can someone test it with TTDPatch and tell me whether the results are similar to what is shown in the subsequent posting? If so, I'd rather see the wiki specs adjusted than the source of both games...
EDIT4: doh...
attached wrong newgrf. Sorry Eddi.