Runescape 3 RS3 NXT 3D model format

!nxtmodelformat

Models in the cache have an lzma wrapper
BIG ENDIAN
1 byte, header 0x03
1 int, compressed size?
1 int, decompressed size?
compressed data


The model data itself
LITTLE ENDIAN

1 byte, header always 0x02?
2 bytes, unknown
1 short, segmentCnt
1 byte, billboard?
1 byte, particle1?
1 bytes, particle2?
segmentCnt TIMES
  1 int, flags
    0b0001 hasFaceColors
    0b0010 hasFaceAlphas (?)
    0b0100 unk1
    0b1000 hasVertexSkins (?)
  1 byte, unknown
  1 short, materialIdx
  1 short, faceCnt
  if hasFaceColors
    faceCnt shorts, face colors
  if hasFaceAlphas
    faceCnt bytes, face alphas?
  if unk1
    faceCnt shorts, unknown
  1 byte, indexCnt (can be up to 5, I think)
  indexCnt TIMES
    1 short, length
    length shorts, index (LODs?)
  1 short, vertCnt
  vertCnt TIMES
    signed short, vertex X
    signed short, vertex Y
    signed short, vertex Z
  vertCnt TIMES
    signed byte, normal X
    signed byte, normal Y
    signed byte, normal Z
  vertCnt TIMES [1]
    signed byte, tangent X
    signed byte, tangent Y
    signed byte, tangent Z
    signed byte, bitangent sign
  vertCnt TIMES
    float16BE, U
    float16BE, V
  if hasVertexSkins
    vertCnt shorts, skinning related? [2]
if billboard
  (TODO)
if particle1
  (TODO)
if particle2
  (TODO)

-----
Faces are built using the first index.
How do face colors get selected for LODs beyond the first?

Models are horizontally flipped?
Textures need to have the repeating edges cropped out for UVs to fit properly?

materialIdx is which file to read in Index 26 Archive 0.
They specify which diffuse/normal/whatever textures to use, etc. and other material settings.

[1] I've not actually tested that these bytes are tangent vectors, but they seem to be. The fourth one is always -128 or 127.

[2] From what I gather, these assign a vertex to a group.
There are keyframes that tell the groups how to move/rotate stored elsewhere. Please correct me if I'm wrong about this.

index26archive0

[WIP] Format of the files in Index 26, Archive 0

BIG ENDIAN

1 byte, materialType (old/new?)

if materialType == 0
  1 byte, texture size?[1]
  1 byte, unknown
  1 int, flags
  if (flags & 0x01) or (flags & 0x10)
    1 int, texture id?
  if (flags & 0x08) or (flags & 0x02)
    1 int, unknown
  1 byte, unknown &7 and >>3&7
  1 int, moreflags
  if (moreflags & 0x40000)
    1 int, unknown
  if (moreflags & 0x80000)
    1 int, unknown
    1 float?, unknown 1.0/value
    1 float?, unknown 1.0/value
    2 ints, unknown
  if (moreflags & 0x10)
    2 ints, unknown
  if (flags & 0x02)
    1 int, unknown
  2 bytes, unknown
  1 byte, unk1
  if (unk1 == 1)
    1 byte, unknown
  if (moreflags & 0x800)
    3 ints, unknown
  1 byte, unk2
  if (unk2 & 0x01)
    1 signed short, unknown value * 0.000060560167
  if (unk2 & 0x02)
    1 signed short, unknown value * 0.000060560167
  1 byte, unk3
  if (unk3 == 0x01)
    2 bytes, unknown
    1 int, unknown
    7 bytes, unknown
    1 short, unknown
else
  1 int, flags
  if (flags & 0x20)
    1 byte, texture size?[1]
    1 int, texture id?
  if (flags & 0x40)
    1 byte, texture size?[1]
    1 int, texture id?
  if (flags & 0x80)
    1 byte, texture size?[1]
    1 int, texture id?
  if (flags & 0x40000)
    1 int, unknown
  if (flags & 0x80000)
    1 int, unknown
    1 float?, unknown 1.0/value
    1 float?, unknown 1.0/value
    2 ints, unknown
  if (flags & 0x1000)
    1 int, unknown
  if (flags & 0x2000)
    1 int, unknown
  if (flags & 0x4000)
    1 int, unknown
  if (flags & 0x40)
    1 int, unknown
  if (flags & 0x8000)
    1 int, unknown
  if (flags & 0x800)
    3 ints, unknown
  if (flags & 0x10000)
    1 int, unknown
  if (flags & 0x20000)
    1 int, unknown
  if (flags & 0x100)
    1 signed short, unknown value * 0.000060560167
  if (flags & 0x200)
    1 signed short, unknown value * 0.000060560167
  1 byte, unknown &7 and >>3&7
  2 bytes, unknown
  1 bytes, unk1
  if (unk1 == 1)
    1 byte, unknown
  1 short, unknown
  1 byte, unknown



-----
[1] some var set to 64,128,256,512,1024 depending on the value read


mat type 1
  second texture: R channel = emission, G = normal G, B = normal B, Alpha = normal R
  third texture: R channel = metal, G = roughness, B = ?

Raksha with textures. Two models, one is just the spikes.

Are the LODs even used in game?

Still trying to figure out the material type 1 setup. One of the textures has normal map + emission map, the other has metalness + roughness + ??.

Some recent update added new flags for model segments. Haven't had a chance to check what the game code is doing, but flags & 32 seems to indicate an int and 3*that bytes at the end of a segment. Don't really care to look into it further than that, tbh. Not really interested in this anymore.

This is very outdated. If you're looking for info on RS3 model/cache formats then see Skillbert's excellent tool here
https://github.com/skillbert/rsmv