'Matrix' object has no attribute 'z' in world_to_camera_view

Question

I'm trying to use the following code to get 2D points out of Blender. Ultimately my goal is to generate HPGL for a pen plotter but for now I'll be happy with a printed list of coordinates.

Whenever the code calls world_to_camera_view I get the error Matrix object has no attribute z. This appears to be a problem inside the world_to_camera_view function?

I'm at a loss as to how to fix it and/or what data the function is actually expecting?

Thanks for the help!

import bpy  
from bpy_extras.object_utils import world_to_camera_view

scene = bpy.context.scene

# needed to rescale 2d coordinates
render = scene.render
res_x = render.resolution_x
res_y = render.resolution_y
cam = bpy.data.objects['Camera']

current_obj = bpy.context.active_object

scene = bpy.context.scene
camObject = bpy.data.objects [ 'Camera' ]

print("="*40) # printing marker  
for face in current_obj.data.polygons:  
    verts_in_face = face.vertices[:]  
    print("face index", face.index)  
    print("normal", face.normal)  

    coords_2d = [world_to_camera_view(scene, cam, coord) for coord in verts_in_face ]

    # 2d data printout:
    rnd = lambda i: round(i)

    print('x,y')
    for x, y, distance_to_lens in coords_2d:
        print("{},{}".format(rnd(res_x*x), rnd(res_y*y)))

Answer 1

Seems like you are passing a vertex though you named it coord.

verts = current_obj.data.vertices
coords_2d = [world_to_camera_view(scene, cam, verts[index].co) for index in face.vertices ]

face.vertices does not contain a collection of mesh vertices, but a list of vertex indices. You need to retrieve the actual vertex and use its coordinate (v.co).