Your reply allowed me to find and understand and mod what I wanted, and much more, and now enjoy enormously the play. Thank you.
To change from dismounted to mounted replace 256 by 0
To make more spawning points for shooters, copy one of the lines and add a new number at the first value, like 48, 49, 50... you can make many. You can add even to the attackers who will use them temporarely - units will only spawn once at the ofset of battle in these.
And most wonderfuly, you can make many spawn points in open field battles. Again, very simply, by copying the lines and adding a new spawn number at the first entry. Of course, these then have to be manualy put and numbered with the edit mod once at the given scene.
Without forgetting to add above the number of lines added, just such as you would in items_kind or scene_props files when you add a new item or object.
Here are the lines for a simple example:
1) For open field random scenes
The following is the original from mission-templates:
mst_lead_charge lead_charge 2 8
You_lead_your_men_to_battle.
4 1 4160 0 16 12 0
0 4160 0 16 0 0
4 8320 0 16 12 0
4 8320 0 16 0 0
The following is the modified (so that each side has 3 new spawns on which units will spawn only the first time) (4 41 42 43 for one side, 1 11 12 13 for the other):
mst_lead_charge lead_charge 2 8
You_lead_your_men_to_battle.
10 1 4160 0 16 12 0
0 4160 0 16 0 0
4 8320 0 16 12 0
4 8320 0 16 0 0
41 8320 0 16 12 0
42 8320 0 16 12 0
43 8320 0 16 12 0
11 4160 0 16 12 0
12 4160 0 16 12 0
13 4160 0 16 12 0
2) For sieges with belfry scenes.
Original:
mst_castle_attack_walls_belfry castle_attack_walls_belfry 2 -1
You_attack_the_walls_of_the_castle...
13 0 8320 256 16 12 0
0 8320 256 16 0 0
10 4160 256 16 0 0
11 4160 256 16 7 0
15 4160 256 16 0 0
40 135232 256 16 1 0
41 135232 256 16 1 0
42 135232 256 16 1 0
43 135232 256 16 1 0
44 135232 256 16 1 0
45 135232 256 16 1 0
46 135232 256 16 1 0
47 135232 256 16 1 0
Moded: (adding 48 49 50 spawns for defending shooters, and 51 52 53 for attackers small spawns - usualy the lord and the first few units will spawn there, and can make the game more interesting..)
19 0 8320 256 16 12 0
0 8320 256 16 0 0
10 4160 256 16 0 0
11 4160 256 16 7 0
15 4160 256 16 0 0
40 135232 256 16 1 0
41 135232 256 16 1 0
42 135232 256 16 1 0
43 135232 256 16 1 0
44 135232 256 16 1 0
45 135232 256 16 1 0
46 135232 256 16 1 0
47 135232 256 16 1 0
48 135232 256 16 1 0
49 135232 256 16 1 0
50 135232 256 16 1 0
51 8320 0 16 1 0
52 8320 0 16 1 0
53 8320 0 16 1 0
3) For sieges with ladders scenes.
Original:
mst_castle_attack_walls_ladder castle_attack_walls_ladder 2 -1
You_attack_the_walls_of_the_castle...
12 0 8320 256 16 12 0
0 8320 256 16 0 0
10 4160 256 16 0 0
11 4160 256 16 7 0
15 4160 256 16 0 0
40 135232 256 16 1 0
41 135232 256 16 1 0
42 135232 256 16 1 0
43 135232 256 16 1 0
44 135232 256 16 1 0
45 135232 256 16 1 0
46 135232 256 16 1 0
Moded: (same as in belfry scene)
mst_castle_attack_walls_ladder castle_attack_walls_ladder 2 -1
You_attack_the_walls_of_the_castle...
19 0 8320 256 16 12 0
0 8320 256 16 0 0
10 4160 256 16 0 0
11 4160 256 16 7 0
15 4160 256 16 0 0
40 135232 256 16 1 0
41 135232 256 16 1 0
42 135232 256 16 1 0
43 135232 256 16 1 0
44 135232 256 16 1 0
45 135232 256 16 1 0
46 135232 256 16 1 0
47 135232 256 16 1 0
48 135232 256 16 1 0
49 135232 256 16 1 0
50 135232 256 16 1 0
51 8320 0 16 1 0
52 8320 0 16 1 0
53 8320 0 16 1 0
This can make the game enormously interesting..
Thank you again for your help
