TeslaRel410/dpl3-revive/spec/B2Z_FORMAT.md

DIV-BIZ2 (.B2Z / .V2Z) binary geometry format

The format family is wider than its extensions. The game-side pipeline uses the same two encodings under different names: .BGF = binary geometry (magic DIV-BIZ2), .VGF = its text twin (DIV-VIZ2), .BMF = binary material library (a BIZ2 file with only material/texture/ramp blocks, no geometry), .VMF = its text twin. Everything below applies to all of them. Game-side material references are namespaced: stships:eblu4_mtl means material eblu4_mtl in library STSHIPS.VMF/.BMF.

Texture sub-block 0x018 (1996+): BITSLICE — u8 plane index into a .BSL bit-slice texture pack (see SVT_FORMAT.md). Absent = slice 0.

Reverse-engineered from DPL3/BIZREAD.C (© DIVISION Ltd 1994, author PJA) and validated against real models on drive SDA4. This is the object/geometry format consumed by the DPL3 renderer used in Virtual World Entertainment's BattleTech / Red Planet pods. .B2Z and .V2Z share this format.

All multi-byte values are little-endian. Floats are IEEE-754 single precision (the header rejects double-precision files). There is no compression — the stream is a flat sequence of length-delimited, tagged blocks.

1. File layout

"DIV-BIZ2"            8-byte ASCII magic
<block>*             sequence of top-level blocks

Parsing stops at the trailer block (type 0x005).

2. Block header

Every block begins with a 16-bit header, followed by a length field whose width is encoded in the top nibble of the header:

hdr   = u16
sel   = (hdr >> 12) & 0xC
  sel == 0x0  ->  length = u8      (1 byte)   top nibble 0,1,2,3
  sel == 0x4  ->  length = u16     (2 bytes)  top nibble 4,5,6,7
  sel == 0x8  ->  length = u32     (4 bytes)  top nibble 8,9,A,B

length counts the block body only (everything after the length field). The record type is hdr & 0xFFF; the top nibble is purely the length-encoding flag. That is why the source lists each type three times (0x0NNN / 0x4NNN / 0x8NNN) — same record, three body sizes.

3. Top-level block types (hdr & 0xFFF)

Type	Meaning	Body
0x003	Header	sub-blocks (§4)
0x004	Comment	opaque, skip
0x005	Trailer	end of file
0x010	Texture	sub-blocks (§7)
0x020	Material	sub-blocks (§7)
0x030	Ramp	sub-blocks (§7)
0x040	Object	sub-blocks (§5)

4. Header sub-blocks

Type	Name	Body
0x002	version	skip
0x003	date	skip
0x004	time	skip
0x005	scale	f32
0x006	precision	u8 (must be 0 = single)
0x007	filetype	skip
0x009	unit	u8: 0 = model units, 1 = inches (scale by 1/25.4)

5. Object sub-blocks

Type	Name	Body
0x008	object name	NUL-terminated string
0x030	front material	material-ref (§6)
0x031	back material	material-ref (§6)
0x036	vertex format	u8 draw_mode (inherited by patches)
0x041	LOD	payload skipped by original loader
0x042	patch	sub-blocks (§8) — one geogroup
0x032/33/34/35/37	plane / draw-mode / decal / facet / voodoo	skip
0x000/001 (+comment tags)	comment	skip

6. Material reference (used by 0x030 / 0x031)

type = u8
  0 -> none (NULL)
  1 -> named: NUL-terminated material name follows
  2 -> DEFAULT material
  3 -> (back only) same as front

7. Material / Texture / Ramp sub-blocks

Material (top-level 0x020):

Type	Name	Body
0x008	name	string
0x00a	scope	u8
0x021	texture	u8 mode; if mode==2, NUL-terminated texture name
0x023	ambient	3×f32
0x024	diffuse	3×f32
0x025	specular	4×f32
0x026	emissive	3×f32
0x027	opacity	3×f32
0x028	ramp	NUL-terminated ramp name

Texture (top-level 0x010): 0x008 name, 0x00a scope, 0x011 map filename (string), 0x012 minify, 0x013 magnify, 0x014 alpha, 0x015 wrap_u, 0x016 wrap_v, 0x017 detail — the mode fields are each a u8. The bitmap itself lives in an external .SVT file named by 0x011. 0x037 is the SPECIAL hook, a NUL-terminated free-text string mirroring the text source's SPECIAL="..." header field — in practice " SCROLL u0 v0 du dv " UV-drift rates (see SCN_FORMAT, Scrolling textures).

Ramp (top-level 0x030): 0x008 name, 0x00a scope, 0x031 ramp data (color0 = 3×f32, color1 = 3×f32).

8. Patch (geogroup) sub-blocks

Type	Name	Body
0x008	patch name	string
0x030	front material	material-ref (§6)
0x031	back material	material-ref (§6)
0x036	vertex format	u8 draw_mode
0x043	polygon	vertex-list (§9), type = polystrip
0x044	tristrip	vertex-list (§9), type = tristrip
0x045	polystrip	vertex-list (§9), type = polystrip
0x046	pmesh	vertex-list (§9), type = pmesh
0x048/04a/04b	sphere / line / text	not implemented in original; skip
0x032/33/34/35/37	plane / draw-mode / decal / facet / voodoo	skip

draw_mode bits (from dpltypes.h): 0x01 smooth, 0x02 colored, 0x04 luminance, 0x08 textured, 0x10 3d-textured, 0x200 front, 0x400 back.

9. Vertex-list sub-blocks

A primitive's body is itself a sequence of blocks: zero or more connectivity blocks (pmesh only) plus exactly one vertex block. A vertex block's length gives n_floats = length / 4; n_vertices = n_floats / floats_per_vertex. Each vertex is floats_per_vertex consecutive f32s; components live at fixed offsets by format:

Type	f/vert	position	normal	rgba	lum(la)	uv(2)	uvw(3)
0x080	3	0	–	–	–	–	–
0x081	6	0	3	–	–	–	–
0x082	7	0	–	3	–	–	–
0x083	10	0	3	6	–	–	–
0x084	5	0	–	–	3	–	–
0x085	8	0	3	–	6	–	–
0x088	5	0	–	–	–	3	–
0x089	8	0	3	–	–	6	–
0x08a	9	0	–	3	–	7	–
0x08c	7	0	–	–	3	5	–
0x090	6	0	–	–	–	–	3
0x091	9	0	3	–	–	–	6
0x092	10	0	–	3	–	–	7
0x094	8	0	–	–	3	–	5

Connectivity (pmesh only):

• 0x047 triangle connectivity — length/12 triangles, each = 3× i32 vertex indices.
• 0x04d polygon connectivity — u8 verts_per_poly, then (length-1)/(vpp*4) polygons, each = vpp× i32 indices.

Triangulation for export:

• tristrip: triangles (i, i+1, i+2), flipping winding on odd i.
• pmesh: fan each face (f0, fk, fk+1).
• polygon / polystrip: current parser fans the block's vertices — adequate for simple patches; a faithful polystrip walk is a known refinement (see README).

10. Validation

parser/b2z.py decodes the samples with no unrecognized blocks and clean trailers. Semantic checks that confirm correctness:

File	Result
PT_RED.B2Z	material diffuse = (1,0,0) → red; no geometry (a colored point)
PT_WHITE.B2Z	material diffuse = (1,1,1) → white
BALL.B2Z	50 verts / 40 tris, bounds ≈ unit sphere at origin, has normals
TESTBOX.B2Z	5 pmesh parts (blue/red/black/green/yellow), 202 tris, boxy bounds
CANDA_S1.B2Z	Red Planet terrain tile: redrock/water materials, inch units, UV coords