File Format Compressing Faces?

Zeealex · Jan 2021

Hey all! so I'm making a set of mod tools for a couple of video games as the tools are either non existent or outdated and no longer work on modern systems.

I'm starting off with a simple converter for the game's model files that will convert them to Wavefront OBJ and then back again.
These are proprietary file formats based off of the old .QOB file format, however they are not the same.

Just a note: This is my first time taking on a project such as this so I apologise if there's something i've missed or if I sound a bit 'nooby'

I've been able to get the converter dumping the correct vertex positions into an OBJ file and I've verified this. However the faces are a little odd/tricky.

I'm testing the converter for one of the file formats on a small sample model which i have access to, and this model is expected to have 30 triangular faces and 28 vertices.
However with the face section of the model, it is impossible for it to have this many faces without some kind of compression/math being applied either on the engine or rendering API level.

The face section is 96 bytes long. With a byte in the geometry properties section of the file stating that the face section length is actually only half that size, at 48 bytes.
Each vertex index definition for the face takes up 2 bytes alone.
Assuming we're dealing with Triangular faces here with no other properties such as normal and UV indices, that gives us a possibility for either 16 faces (assuming a 96 byte section length) or 8 Faces (assuming a 48 byte section length)

Furthermore, spitting these indices into a face section of an OBJ file gives me the following:

f 1 2 3
f 4 5 6
f 7 8 8
f 9 9 10
f 11 10 12
f 13 14 15
f 16 16 17
f 17 14 18
f 12 19 12
f 20 11 20
f 21 19 21
f 22 23 22
f 24 25 24
f 26 2 26

which gives me this when I verify:

Image: https://us.v-cdn.net/5021068/uploads/editor/y4/pfbzpw69slw4.png

The duplication of vertex indices indicates to me that I'm doing something wrong here.

I manually reconstructed the face section and this is what I got:
f 1 2 3
f 2 24 26
f 4 5 6
f 4 27 25
f 4 2 26
f 4 3 2
f 4 3 5
f 6 27 28
f 6 27 4
f 7 6 5
f 8 7 6
f 9 10 11
f 11 10 12
f 13 14 15
f 15 16 14
f 17 14 18
f 12 18 14
f 12 10 13
f 12 13 14
f 18 12 19
f 12 19 20
f 20 11 12
f 20 21 11
f 21 19 20
f 22 21 19
f 21 23 22
f 24 22 23
f 24 25 22
f 24 25 26
f 25 26 4

which gives me:

Image: https://us.v-cdn.net/5021068/uploads/editor/yd/qt3xqc6s1vel.png

I've got the original file with some information I've pulled about the file format if needed.

Has anyone seen something like this before? can anyone advise on what else to try? I'm particularly curious about it giving a 48 byte section length as opposed to 96, as in other, larger models it gives the correct section length.

Any help will be appreciated on this side!

poopipe · Jan 2021

Is it possible it's tri-stripped?
You only need 2 verts to define a mid strip Tri if that's the case and might explain the funny numbers.

Klunk · Jan 2021

can you post the original .QOB file ?

Zeealex · Jan 2021

Klunk said:

can you post the original .QOB file ?

https://drive.google.com/file/d/127FzMskJjBRH6Ga5QvHzmkFNVHRK-PfJ/view?usp=sharing
I'll get the data types and file information for you shortly.

poopipe said:

Is it possible it's tri-stripped?
You only need 2 verts to define a mid strip Tri if that's the case and might explain the funny numbers.

Interesting, I thought it may have been defining something similar, I thought it was possibly defining edges though, lol! is there any more information on Tri-stripping and how to program my software to calculate the correct faces anywhere?

Zeealex · Jan 2021

Hopefully the formatting doesn't bork
XQOB File

Header Size – 16 Bytes

File Structure:

MEMB

MTRL

GEOM

MESH

SLIT

MDLT

PHYS

MODL

XCHR (XSKA only)

File Header

Location	Length	Type	Description	Value
0	4	Unsigned int	File Length	Variable
4-7	4	String/Date	XQOB File Header – Contains Date	XQOB - 04/03/2005 02:13:44
2	4	Unsigned Int	Mesh Count	Usually 2, Sometimes 3

Texture

Location	Length	Type	Description	Value
TXTR+1	4	Unsigned Int	Texture Index 1	1
TXTR+4	4	Unsigned Int	Texture 1 Size	512
TXTR+5	4	Unsigned Int	Texture Index 2	2
TXTR+8	4	Unsigned Int	Texture 2 Size	512
TXTR+9	4	Unsigned Int	TextureCount	Typically, 2
16	4	Unsigned Int	Section Size for TextureList (In bytes)	Variable
36	4	Unsigned Int	Texture 1 Name Length (Bytes)	Variable
Variable	4	Unsigned Int	Subsequent Texture Name Lengths occur immediately after Preceding texture name	Variable

Member

Location	Length	Type	Description	Value
MEMB-4	4	Unsigned Int	Section Length	Variable
MEMB-8	4	Unsigned Int		123456
MEMB+1	4	Unsigned Int	Object Count	Variable
MEMB+24	4	Unsigned Int	Vertex section length
MEMB+80	4	float	First vertex position	variable
MEMB+Vertexes	2	Ushort	Face vertex indices	variable

XQOB File Bytes Per Vertex: 24

XSKA File Bytes Per Vertex: 48

Material

Location	Length	Type	Description	Value
MTRL-4	4	Unsigned Int	Section Length	Variable
MTRL+1	4	Unsigned Int	Illumination Model	Typically, 2
MTRL+9	16	Unsigned Int	Material header	Variable
MTRL+24	80	Variable	Material parameters	Variable
MTRL+104	36	Unsigned Int	Material Signature	Variable

Geometry

Location	Length	Type	Description	Value
GEOM-4	4	Unsigned Int	Section Length	Multiples of 76 depending on number of elements
GEOM+17	4	Unsigned Int	Vertex Section Length 1 – this is 0 if there is only one object	Variable
GEOM+25	4	Unsigned Int	Face Section 1 length	Variable
GEOM + 92	4	Unsigned Int	Vertex Section 1 + Face Section 1 + Vertex Section 2	Variable
GEOM + 101	4	Unsigned Int	Face Section 2 length + 1	Variable
GEOM+9	2	Unsigned Short	Object 1 Vertex Count	Variable

Mesh

Location	Length	Type	Description	Value
MESH-4	4	Unsigned Int	Section Length	Variable

SLIT

Location	Length	Type	Description	Value
SLIT-4	4	Unsigned Int	Section Length	Variable

MDLT – Possible UVW definitions

Location	Length	Type	Description	Value
MDLT-4	4	Unsigned Int	Section Length	Variable

Physics

Location	Length	Type	Description	Value
PHYS-4	4	Unsigned Int	Section Length	Variable

MODL

Location	Length	Type	Description	Value
MODL-4	4	Unsigned Int	Section Length	Variable
MODL+4	4	Unsigned Int		256
MODL+12	4	Unsigned Int		-256

XCHR – Skeleton & Weights Definition

Location	Length	Type	Description	Value
XCHR-4	4	Unsigned Int	Section Length	Variable

Klunk · Jan 2021

are you sure about the file, there's next to nothing in the GEOM or MESH probably not enough data to make a cube.

Zeealex · Jan 2021

Klunk said:

are you sure about the file, there's next to nothing in the GEOM or MESH probably not enough data to make a cube.

Vertices and Faces are in the MEMB section, the first vertex starts 80 bytes after the 'MEMB' string, then the faces start immediately after the vertices. GEOM and MESH are just properties sections.

Klunk · Jan 2021

it also seems to be in big endian byte order or there is some very odd alignment going on

the raw data suggest first five faces would be...

1 2 3
4 5 6
7 7 8
8 9 10
9 11 12

that's one bad "chunk" file implementation..... the point of the doom chunk file format is the sizeof chunk in bytes (4 bytes after the 4 byte tag) takes you directly to the start of the next chunk tag without fail.

so each tag is 16 bytes long... so something like
<int, int, int(tag data length after tag), 4 char code tag>

Zeealex · Jan 2021

Interesting! If I switch to big endian though all of the section lengths and properties etc no longer make sense, whereas they do in little endian. I can't imagine the file switches endianness half way through, right?

Klunk · Jan 2021

it's not big endian, I was expecting at least 2 byte alignment (it makes it easier to "read" in a hex editor) but it's byte aligned which threw me

(I think it's because they don't pad the texture name

Klunk · Jan 2021

seems i get the same as you

Image: https://us.v-cdn.net/5021068/uploads/editor/6i/np0ap1e7mkqn.jpg

can't think of any reason they would want to compress the face indices

so i'm not sure whats going on

Klunk · Jan 2021

yep it's striped

so the indice
12345678...
mean
faces
123
234
345
456
etc

the duplications are a way of continuing the strip without the face being visible

so it's visible with wireframe

Image: https://us.v-cdn.net/5021068/uploads/editor/sp/v70gndbtbb98.jpg

but not without

obviously you need to solve the ordering issue .... could be alternating

Zeealex · Jan 2021

Klunk said:

yep it's striped

so the indice
12345678...
mean
faces
123
234
345
456
etc

the duplications are a way of continuing the strip without the face being visible

so it's visible with wireframe

but not without

You're Awesome!

So how would I go about programming the file converter to factor in the tri-stripping so I can convert to OBJ? I've programmed it in C#, I understand probs not the best language to use but it's just file I/O so didn't think much of it :')

is there a specific algorithm I need to use?

Klunk · Jan 2021

yep alternating.... my mxs code

faceindices = for f = 1 to nindices collect ( 1 + ReadShort bstream unsigned; )

faces = for f = 1 to faceindices.count - 2 collect

(

face = [0,0,0];

face.x = faceindices[f+2];

face.y = faceindices[f+1];

face.z = faceindices[f];

if mod f 2 == 0 then swap face.x face.y

face

)

Image: https://us.v-cdn.net/5021068/uploads/editor/6r/28l4biqg2kyn.jpg

Zeealex · Jan 2021

Awesome! thanks for the code snippet! Would I also have to factor in something similar for the UV definitions?

Klunk · Jan 2021

not sure, I didn't delve that far in, that is a rabbit hole for you

also the 4 bytes after

MEMB+24

4

Unsigned Int

Vertex section length

is the number of face indices (if you didn't know already)

File Format Compressing Faces?

Replies

File Header

Texture

Member

Material

Geometry

Mesh

SLIT

MDLT – Possible UVW definitions

Physics

MODL

XCHR – Skeleton & Weights Definition