M2 MD21 and triangles

[VesperCore]

Hello there,

in my meshBuilder, I've having an issue currenctly.

There is those new .M2 files that can contains 8 bytes before the real stuff begin;

basically:

MAGIC = MD21
UNK_INT = XXXXX
MAGIC = MD20
.... normal for the rest


so I just decided to jump 8 bytes in case magic == MD21.

But, now another story, when magic == MD21, the first triangle at OffsetBoundingTriangles will have wrong values:
I read if first ushort == ushort.MaxValue (65536)

then I dump the 4 first bytes:

Triangle error, 4 bytes extracted: FF FF FF FF from OffsetBoundingTriangles
Triangle error, 4 bytes extracted: FF FF 2 0 from OffsetBoundingTriangles
Triangle error, 4 bytes extracted: FF FF FF FF from OffsetBoundingTriangles
Triangle error, 4 bytes extracted: FF FF 3 0 from OffsetBoundingTriangles
Triangle error, 4 bytes extracted: FF FF 0 0 from OffsetBoundingTriangles

Any idea why we would have FF FF instead of the first value, or even FF FF FF FF ?

It's especially happend on map Troll Raid @ 22_32 for me

It will cause a OutOfBoundException because there is no vertex at index 65536 and will crash into recast because of unreadable pointer.

How do you know where the first leggit triangle ushort begin ?


Here an example of FF FF FF FF + MD21
World\\Expansion06\\Doodads\\Artifact\\7AF_Artifacthub_AltarMage.m2 ::: TinyUpload.com - best file hosting solution, with no limits, totaly free
offsettriangle = 194544

Here an example of FF FF 2 0 + MD21
World\\Expansion06\\Doodads\\Legion\\7LG_Legion_Spire01.m2

Here an example of FF FF 3 0 + MD21
World\\Expansion06\\Doodads\\Legion\\7LG_Legion_Portal02.m2 ::: TinyUpload.com - best file hosting solution, with no limits, totaly free
offsettriangle = 130608

Here an example of FF FF 0 0 + MD21
World\\Expansion06\\Doodads\\Suramar\\7SR_CityWillowTree_B01.m2

I've uploaded 2 of them if you wanna get an eye over the file with your hex editor or w/e

Here hexeditor screenshot: https://i.imgur.com/0P1B57u.png

Should I jump 8 bytes further here too ? If yes, then what is the triangle count ?

It would make
00 01 => short
00 02 => short
00 01 => short


and

00 01 => short
00 02 => short
00 02 => short


Edit:

When I read header, I do the 8bytes jump, however, when I was reading the other, I did not do the 8 bytes, so the lenght of triangles, read from header is fine, but I must add 8 bytes from the offset too ?

Can you confirm me this ?

[VesperCore]

Well, nevermind, I was thinking for some reasons that the offset would be from the beginning of the .m2 file, when indeed, it's from the beginning of the inner m2 file that start at magic = MD20, so I indeed need to add 8 bytes when reading triangles, bounding, and stuff.

[ioctl]

Hello there,

in my meshBuilder, I've having an issue currenctly.

There is those new .M2 files that can contains 8 bytes before the real stuff begin;

basically:

MAGIC = MD21
UNK_INT = XXXXX
MAGIC = MD20
.... normal for the rest

The new model files are chunked with explicit chunk sizes -- similar to ADT's. Your unknown field is the size of the first chunk (the MD21), chunk name and size field not included. The payload of the MD21 chunk is just a plain old MD20 file. So far, all of the m2's I've looked at contain a MD21 wrapper around an MD20 file, followed by a four byte (again, not counting header) SFID chunk.

It feels like they wanted to add metadata to the MD20 format, so they just wrapped it in their explicit chunking format and tacked it on at the end.