Reading mesh object from json

Hi @owen​,

Sorry, there was a bit of an error in the first workspace - the first value in the faces quartet is a flag, not an index, so the output geometry is a little off. Please try this update.

There also seem to be some sub-elements within some of the features. I will look into ways to extract these as well, if needed.

Thanks for that link. I did find another codebase that suggests that the flag is to designate 3 or 4 sided faces in the mesh. If you find some data with 4 sided faces, you may want to try the Speckle output to confirm.

There are a couple of ways I could handle the sub-elements:

• create separate feature with a parent id pointing to the main feature
• create the hierarchical geometry structure, with the attributes as geometry traits at the appropriate level

The second method is how we read IFC data, and is a pain to work with for most users. The first method would be the simplest, and I think the most useful. What are your thoughts?

Hi @daveatsafe​, @owen​,

I'm very glad to have found this post, it helped us greatly in processing the JSON output from Speckle. Considering three- and four-sided faces, we changed the python code a bit. For further quests here is the code we use: 

import fme
import fmeobjects
 
 
def makeGeom(feature):
    # read faces and vertices from attributes
    faces = feature.getAttribute('faces{}')
    vertices = feature.getAttribute('vertices{}')
    
    # create new Mesh geometry
    mesh = fmeobjects.FMEMesh()
    
    # create vertex XYZ from three vertex list entries
    for v in range(int(len(vertices)/3)):
        mesh.appendVertex(vertices[v*3],vertices[v*3+1],vertices[v*3+2])
    
    # create face from four or five face list vertex entries
    i = 0
    while i < len(faces):
        if faces[i] == 0:
            mesh.addMeshPart(0,[faces[i+1],faces[i+2],faces[i+3]],None,None)
            i = i + 4
        else:
            mesh.addMeshPart(0,[faces[i+1],faces[i+2],faces[i+3],faces[i+4]],None,None)
            i = i + 5
        
    # set geometry to new Mesh
    feature.setGeometry(mesh)