This are the first results on Xenogears battle background.
First of all they are at 246419 - 253729 sectors of the disk. There are pairs of two files. First one are the battle background itself. The purpose of second one are still unknown.
Here are description of .bb (battle background) files
0x0000 u32 - number of sectors (always 05 00 00 00)
0x0004 u32 - 6 offsets to the blocks (last one offset to the end of file)
0x001C - till the next offset - tim textures and background (16 bit per piexl without CLUT)
# textures header
all offsets start from beginning of this block
0x0000 u32 - number of tim
next are for bytes offsets to tim
i still need more time to look at the header of each tim, but 0xC offsets from the beginning of each tim are height and width (2 bytes each)
# mech header
all offsets start from beginning of this block
0x0000 u32 - number of blocks
00 00 00 00 00 00 00 00 00 00 00 00 - unknown (as I see it always filled with zero)
#header to mech block
00 00 - unknown (zero)
84 00 - number of vertex
73 00 - number of mech (probably) (in this case each mech are always 12 bytes)
02 00 - unknown
28 01 00 00 - offset to vertex block
28 01 00 00 - offset to vertex block (again?)
48 05 00 00 - offset to next block (or end of vertex block)
(there something between start of next vertex block and beginning of vertex itself)
80 3B 00 00 - offset to mech block (probably)
00 00 00 00 - unknown (zero)
00 00 00 00 - unknown (zero)
95 01 74 FF 4F 00 53 01 B2 05 F2 FF 1D 03 00 00 00 00 00 00 B8 11 00 00 - unknown (perhaps some flags)
next are the second block and so, till the vertex data.
vertex format are the same as in FFVII
8 byte per vertex:
3 u16 x,y,z
1 u16 (unknown, probably textures coordinate or something)