blerex.py

import bpy
from bpy import context
import numpy as np

REX_BLOCK_HEADER_SIZE = 16
REX_MESH_HEADER_SIZE = 128
REX_NOT_SET = np.uint64(0x7fffffffffffffff).byteswap().tobytes()


def mesh_triangulate(me):
    import bmesh
    bm = bmesh.new()
    bm.from_mesh(me)
    bmesh.ops.triangulate(bm, faces=bm.faces)
    bm.to_mesh(me)
    bm.free()


filepath = "/tmp/simple_rex.rex"
print('save to {}'.format(filepath))

obj = context.object
mesh = obj.data

mesh_triangulate(mesh)
numtriangles = len(mesh.polygons)

block_byte_count = REX_BLOCK_HEADER_SIZE + REX_MESH_HEADER_SIZE \
             + len(mesh.vertices)*12 + 0*12 + 0*8 + 0*12 + numtriangles*12

version = np.uint16(1).byteswap().tobytes()
blocktype = np.uint16(3).byteswap().tobytes()  # 3 = mesh
blocksize = np.uint32(block_byte_count).byteswap().tobytes()
blockid = np.uint64(0).byteswap().tobytes()

# mesh description
lod = np.uint16(1).byteswap().tobytes()
maxLod = np.uint16(1).byteswap().tobytes()
nrOfVtxCoords = np.uint32(len(mesh.vertices)).byteswap().tobytes()  # number of vertex coordinates
nrOfNorCoords = np.uint32(0).byteswap().tobytes()  # number of normal coordinates (can be zero)
nrOfTexCoords = np.uint32(0).byteswap().tobytes()  # number of texture coordinates (can be zero)
nrOfVtxColors = np.uint32(0).byteswap().tobytes()  # number of vertex colors (can be zero)
nrTriangles = np.uint32(numtriangles).byteswap().tobytes()  # number of triangles

materialId = REX_NOT_SET  # np.uint64(1)  # id which refers to the corresponding material block in this file
name = bytearray(b'testmesh')
size = np.uint16(len(name)).byteswap().tobytes()  # size of the following string name

startDataBlock = 128
startVtxCoords = np.uint32(startDataBlock).byteswap().tobytes()  # start vertex coordinate block (relative to mesh block start)
startNorCoords = np.uint32(startDataBlock + len(mesh.vertices)*12).byteswap().tobytes()  # start vertex normals block (relative to mesh block start)
startTexCoords = np.uint32(startDataBlock + len(mesh.vertices)*12).byteswap().tobytes()  # start of texture coordinate block (relative to mesh block start)
startVtxColors = np.uint32(startDataBlock + len(mesh.vertices)*12).byteswap().tobytes()  # start of colors block (relative to mesh block start)
startTriangles = np.uint32(startDataBlock + len(mesh.vertices)*12).byteswap().tobytes()  # start triangle block for vertices (relative to mesh block start)


header = blocktype + version + blocksize + blockid
meshheader = lod + maxLod + nrOfVtxCoords + nrOfNorCoords + nrOfTexCoords \
             + nrOfVtxColors + nrTriangles + materialId + size + name

meshdata = bytearray()

for v in mesh.vertices:
    meshdata = meshdata + np.array(v.co[:]).astype('float32').byteswap().tobytes()

for p in mesh.polygons:
    for vid in p.vertices:
        meshdata = meshdata + np.uint32(vid + 1).byteswap().tobytes()

with open(filepath, 'w+b') as f:
    f.write(header + meshheader + meshdata)