Commit 13c8063

The following part is a bit complex and requires heavy understanding of the UE4 internals.

Just read the code comments, we now need to extract the data in the dae file (vertices, uvs and normals) and build a LOD (Level of Detail) for the StaticMesh (a StaticMesh can have multiple LOD's, each one is a different Mesh).

In this case we use a single LOD (the LOD0). Pay attention to the data manipulation (using numpy). The collada format has different convention in respect to UE4. We flip UVs vertically and we swap axis to have Z on top (instead of y)

from unreal_engine.classes import PyFactory, StaticMesh, Object, Class

import unreal_engine as ue

from collada import Collada

from unreal_engine.structs import StaticMeshSourceModel, MeshBuildSettings

from unreal_engine import FRawMesh

import numpy

class ColladaFactory(PyFactory):

def __init__(self):

# inform the editor that this class is able to import assets

self.bEditorImport = True

# register the .dae extension as supported

self.Formats = ['dae;Collada']

# set the UClass this UFactory will generate

self.SupportedClass = StaticMesh

def PyFactoryCreateFile(self, uclass: Class, parent: Object, name: str, filename: str) -> Object:

# load the collada file

dae = Collada(filename)

ue.log_warning(dae)

# create a new UStaticMesh with the specified name and parent

static_mesh = StaticMesh(name, parent)

# prepare a new model with the specified build settings

source_model = StaticMeshSourceModel(BuildSettings=MeshBuildSettings(bRecomputeNormals=False, bRecomputeTangents=True, bUseMikkTSpace=True, bBuildAdjacencyBuffer=True, bRemoveDegenerates=True))

# extract vertices, uvs and normals from the da file (numpy.ravel will flatten the arrays to simple array of floats)

triset = dae.geometries[0].primitives[0]

vertices = numpy.ravel(triset.vertex[triset.vertex_index])

# take the first uv channel (there could be multiple channels, like the one for lightmapping)

uvs = numpy.ravel(triset.texcoordset[0][triset.texcoord_indexset[0]])

normals = numpy.ravel(triset.normal[triset.normal_index])

# move from collada system (y on top) to ue4 one (z on top, forward decreases over viewer)

for i in range(0, len(vertices), 3):

xv, yv, zv = vertices[i], vertices[i+1], vertices[i+2]

# invert forward

vertices[i] = zv * -1

vertices[i+1] = xv

vertices[i+2] = yv

xn, yn, zn = normals[i], normals[i+1], normals[i+2]

# invert forward

normals[i] = zn * -1

normals[i+1] = xn

normals[i+2] = yn

# fix uvs from 0 on bottom to 0 on top

for i, uv in enumerate(uvs):

if i % 2 != 0:

uvs[i] = 1 - uv

# create a new mesh, FRawMesh is an ptopmized wrapper exposed by the python plugin. read: no reflection involved

mesh = FRawMesh()

# assign vertices

mesh.set_vertex_positions(vertices)

# uvs are required

mesh.set_wedge_tex_coords(uvs)

# normals are optionals

mesh.set_wedge_tangent_z(normals)

# assign indices (not optimized, just return the list of triangles * 3...)

mesh.set_wedge_indices(numpy.arange(0, len(triset) * 3))

# assign the FRawMesh to the LOD0 (the model we created before)

mesh.save_to_static_mesh_source_model(source_model)

# assign LOD0 to the SataticMesh and build it

static_mesh.SourceModels = [source_model]

static_mesh.static_mesh_build()

static_mesh.static_mesh_create_body_setup()

return static_mesh

re-run the script and import the same file again (by clicking Import in the Content Browser), if all goes well you will end with the duck mesh: