🧵 [REQUEST] Noesis plugin for XMX/LDMX – mesh corruption (index/stride issue)

Hi,

I'm reverse engineering a proprietary XMX / LDMX model format and I'm getting consistent mesh corruption when parsing it.

I'd like help identifying the correct vertex layout and eventually building a Noesis plugin (.fmt or Python) to export to FBX/OBJ.

---

📦 Format info (confirmed)

Header:

4C 44 4D 58 → "LDMX"

Chunks found:

• EMAN (likely "NAME", reversed)

• MNXT (textures)

• VPRG (vertex block)

• INDX (index buffer)

---

🔹 Vertex data

Float data detected:

E0 FE 48 BE → -0.196
48 E7 E7 BE → -0.453
80 09 A7 3C → 0.020

Likely:

• Position (float3)

• followed by normals / UVs / etc.

❗ Unknown:

• vertex stride (suspected 32 / 36 / 40 bytes)

---

🔹 Index buffer

58 44 4E 49 → "INDX"

• Appears to be uint16 (little endian)

Example:

01 00 02 00 03 00

---

⚠️ Problem

Mesh is corrupted:

• degenerate triangles like:

22 00 22 00 22 00
25 00 25 00 25 00

Result:

• collapsed faces

• broken topology

---

🧠 Suspected causes

• Wrong vertex stride

• Incorrect index offset

• Vertex count mismatch

• Possible mixed endianness

---

📂 Textures

Paths inside file:

d:\FS\tex_zb01.zip/:xxxx.dds

→ DDS inside ZIP archives

---

🎯 What I need

• Help identifying correct vertex layout / stride

• Eventually a Noesis plugin that:

  • reads vertices correctly

  • fixes mesh

  • exports to FBX/OBJ

---

🧪 I can provide

• Sample files

• Hex dumps

• Test results

---

❓ Question

Has anyone seen a similar format or can help determine the correct vertex layout / stride?

Best result, but it's not entirely correct; it always reads shitty padding or interspersed garbage. One or more triangles always come out wrong, but it's the best version—the one where the mesh turns out almost perfect...

Almost all the files to be converted are located at: https://github.com/randalfcastro-tech/xmx-testing

from inc_noesis import *
import noesis
import rapi
import struct

# =========================
# REGISTER
# =========================

def registerNoesisTypes():
handle = noesis.register("XMX REAL FINAL STABLE", ".xmx")
noesis.setHandlerTypeCheck(handle, xmxCheckType)
noesis.setHandlerLoadModel(handle, xmxLoadModel)
return 1

def xmxCheckType(data):
return 1 if data[:4] == b"LDMX" else 0


# =========================
# FIND REAL REGION
# =========================

def findRealMeshRegion(data):
vprg = data.find(b"VPRG")
if vprg == -1:
return -1, -1

xtrv = data.find(b"XTRV", vprg)
xdni = data.find(b"XDNI", xtrv)

return xtrv, xdni


# =========================
# VERTICES (REAL)
# =========================

def parseVertices(data):
xtrv, xdni = findRealMeshRegion(data)

if xtrv == -1 or xdni == -1:
print(" Missing real mesh blocks")
return None

start = xtrv + 4
end = xdni

bs = NoeBitStream(data)
bs.seek(start)

verts = []
norms = []
uvs = []

stride = 32
MAX_VERTS = 200000

while bs.tell() + stride <= end and len(verts) < MAX_VERTS:
try:
x = bs.readFloat()
y = bs.readFloat()
z = bs.readFloat()

nx = bs.readFloat()
ny = bs.readFloat()
nz = bs.readFloat()

u = bs.readFloat()
v = bs.readFloat()

# sanity check (evita basura)
if abs(x) > 10000 or abs(y) > 10000 or abs(z) > 10000:
break

verts.append((x,y,z))
norms.append((nx,ny,nz))
uvs.append((u,1.0-v))

except:
break

print(" Vertices:", len(verts))
return verts, norms, uvs


# =========================
# INDICES (REAL)
# =========================

def parseIndices(data):
_, xdni = findRealMeshRegion(data)

if xdni == -1:
print(" No XDNI")
return None

bs = NoeBitStream(data)
bs.seek(xdni + 4)

indices = []
MAX_INDICES = 500000

while bs.tell() + 2 <= len(data) and len(indices) < MAX_INDICES:
indices.append(bs.readUShort())

print(" Indices:", len(indices))
return indices


# =========================
# STRIP → TRIANGLES
# =========================

RESTART = 0xFFFF

def stripToTriangles(indices, vertCount):
tris = []
flip = False

for i in range(len(indices)-2):
a = indices[i]
b = indices[i+1]
c = indices[i+2]

if a == RESTART or b == RESTART or c == RESTART:
flip = False
continue

if a == b or b == c or a == c:
flip = not flip
continue

if a >= vertCount or b >= vertCount or c >= vertCount:
continue

if flip:
tris.extend([b, a, c])
else:
tris.extend([a, b, c])

flip = not flip

return tris


# =========================
# BUILD
# =========================

def buildMesh(verts, norms, uvs, indices):

tris = stripToTriangles(indices, len(verts))

# sanitizar
clean = []
maxVert = len(verts)

for i in tris:
if not isinstance(i, int):
continue
if i < 0 or i >= maxVert:
continue
clean.append(i)

clean = clean[:(len(clean)//3)*3]

if len(clean) < 3:
print(" No valid triangles")
return

vb = b''.join([struct.pack("3f", *v) for v in verts])
nb = b''.join([struct.pack("3f", *n) for n in norms])
ub = b''.join([struct.pack("2f", *u) for u in uvs])

rapi.rpgBindPositionBuffer(vb, noesis.RPGEODATA_FLOAT, 12)
rapi.rpgBindNormalBuffer(nb, noesis.RPGEODATA_FLOAT, 12)
rapi.rpgBindUV1Buffer(ub, noesis.RPGEODATA_FLOAT, 8)

try:
ib = struct.pack("%dH" % len(clean), *clean)
except Exception as e:
print(" PACK ERROR:", e)
return

rapi.rpgCommitTriangles(
ib,
noesis.RPGEODATA_USHORT,
len(clean),
noesis.RPGEO_TRIANGLE,
1
)


# =========================
# MAIN
# =========================

def xmxLoadModel(data, mdlList):
ctx = rapi.rpgCreateContext()

parsed = parseVertices(data)
if not parsed:
return 0

verts, norms, uvs = parsed

indices = parseIndices(data)
if not indices:
return 0

print(" Building mesh")

buildMesh(verts, norms, uvs, indices)

mdl = rapi.rpgConstructModel()
mdlList.append(mdl)

return 1

fmt_parser_xmx.py

Edited 13 hours ago13 hr by Ralp1670

degenerated triangles: just a wild guess (without checking the details): maybe the indices of those models with that problem are DWords, not shorts?

No, son.

Edited 12 hours ago12 hr by Ralp1670

15 minutes ago, shak-otay said:

degenerated triangles: just a wild guess (without checking the details): maybe the indices of those models with that problem are DWords, not shorts?

👉 NOT DWORD (uint32)
✔ These models correctly use UINT16.

1 hour ago, Ralp1670 said:

No, son.

Your disrespect forces me to leave the thread. Good luck.

6 minutes ago, shak-otay said:

Your disrespect forces me to leave the thread. Good luck.

6 minutes ago, shak-otay said:

Your disrespect forces me to leave the thread. Good luck.

Friend, I thought you would ask questions or present arguments, but you are taking things for granted that simply aren't true; even if it sounds like a clever answer, it isn't backed by facts—and I’ve tried to be as polite as possible...

3 hours ago, Ralp1670 said:

No, son.

Really.. man this is so stupid answer!

4 hours ago, Ralp1670 said:

I'm reverse engineering a proprietary XMX / LDMX model format and I'm getting consistent mesh corruption when parsing it.

Can you tell us which game (?) uses this .xmx format?

Since there is FFFF strip terminator it could be some xbox / 360 game. But now it's a history. Also i can't see any samples.