Hello,

I have a set of Blender objects that I want to export as a single object.
I process each object, adding vertices, triangles for the exported object.
Dealing with materials for the processed objects is not mentionned here.

Is the following processing principle correct? (I'm asking, as I don't quite get what I expect: The export works.
I have all the expected objects but objects are not properly positioned in the exported world).

Thanks in advance for advices and help.

Code:

# obj : object being processed # data : its mesh data # For the first object, the following is stored (first 2 instructions because of axis changes): first_obj_transform = Matrix.Rotation(radians(90), 4, 'X') first_obj_transform *= Matrix.Scale(-1, 4, Vector((0, 0, 1))) first_obj_matrix = obj.matrix_world.copy() Then, for each object (obj) and its mesh (data):    obj_matrix = obj.matrix_world.copy()    data.calc_tessface() # Compute and update the list of tessellated faces (faces of 3 or 4 vertices)    ...    # Take into account the axis changes:    obj_matrix = obj_matrix * first_obj_transform    # Pivot in world coordinates    pivot = Vector([obj.matrix_world.translation[0], obj.matrix_world.translation[1], obj.matrix_world.translation[2]])    # Update pivot applying the axis transformation    new_pivot = first_obj_transform * pivot    obj_matrix.translation = new_pivot[0], new_pivot[1], new_pivot[2]           # Get vertices, normals and UVs from the faces    for face_num, face in enumerate(data.tessfaces):    ...       # Process triangle or quad       for face_num, face in enumerate(data.tessfaces):          f_v = face.vertices    ...          # Process each vertex for the found triangles          # convert local object coordinates to local coordinates of first object          local_vertex = data.vertices[f_v[vert_num]].co * obj_matrix  * first_obj_matrix.inverted()          local_vertex.x += first_obj_matrix.translation[0] - obj_matrix.translation[0]          local_vertex.y += first_obj_matrix.translation[1] - obj_matrix.translation[1]          local_vertex.z += first_obj_matrix.translation[2] - obj_matrix.translation[2]          # Add the converted vertices in the export    ...

you sure you want to convert vertex coordinates from local to 1st object's coordinate system???
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CoDEmanX wrote:

you sure you want to convert vertex coordinates from local to 1st object's coordinate system???

Yes, in the export format, the object format is in local coordinates + world matrix.

data was created as:
data = obj.to_mesh(bpy.context.scene, True, 'PREVIEW')
... and what about using data.transform?

Code:

data = obj.to_mesh(bpy.context.scene, True, 'PREVIEW') # <<<<< # For the first object, the following is stored (first 2 instructions because of axis change): first_obj_transform = Matrix.Rotation(radians(90), 4, 'X') first_obj_transform *= Matrix.Scale(-1, 4, Vector((0, 0, 1))) first_obj_matrix = obj.matrix_world.copy() # Pivot of first object in world coordinates pivot = Vector([first_obj_matrix.translation[0], first_obj_matrix.translation[1], first_obj_matrix.translation[2]]) # Update pivot applying the axis change new_pivot = first_obj_transform * pivot # Update matrix to apply axis rotation first_obj_matrix *= first_obj_transform # Update matrix to apply pivot new coordinates in new axis system first_obj_matrix.translation = new_pivot[0], new_pivot[1], new_pivot[2] # Update rotation matrix to apply pivot new coordinates first_obj_transform.translation = new_pivot[0], new_pivot[1], new_pivot[2] Then, for each object (obj) and its mesh (data created with to_mesh):    obj_matrix = obj.matrix_world.copy()    # Take into account the axis changes:    obj_matrix = obj_matrix * first_obj_transform        data.transform(obj_matrix) # <<<<<        data.calc_tessface() # Compute and update the list of tessellated faces (faces of 3 or 4 vertices)    ...           # Get vertices, normals and UVs from the faces    for face_num, face in enumerate(data.tessfaces):    ...       # Process triangle or quad       for face_num, face in enumerate(data.tessfaces):          f_v = face.vertices    ...          # Process each vertex for the found triangles          # convert world object coordinates to local coordinates of first object          local_vertex = data.vertices[f_v[vert_num]].co * first_obj_matrix.inverted()          # Add the converted vertices in the export    ... # to_mesh() created a new mesh so remove it bpy.data.meshes.remove(data)