Help with projection Matrix

[josephbiko]

I am trying to calculate the pixel coordinates of the landmarks.
(Parameters are copied from the render helper).

def viewport(x, y, w, h):
    x, y, w, h = map(float, (x, y, w, h))
    return np.matrix([[w/2, 0  , 0,x+w/2],
                      [0  , h/2, 0,y+h/2],
                      [0  , 0  , 0.5,  0.5],
                      [0  , 0  , 0,    1]])

size = 800

frustum_ = {'near': 0.01, 'far': 3.0, 'height': 800, 'width': 800}
camera_params = {'c': np.array([400, 400]),
                 'k': np.array([-0.19816071, 0.92822711, 0, 0, 0]),
                 'f': np.array([4754.97941935 / 2, 4754.97941935 / 2])}

landmarks = mesh_points_by_barycentric_coordinates(m.v,m.f,flame_embedding['lmk_face_idx'],flame_embedding['lmk_b_coords'])
 


pose_mat = [[1, 0, 0, 0],
            [0, 1, 0, 0],
            [0, 0, 1, 1],
            [0, 0, 0, 1]]

camera = pyrender.IntrinsicsCamera(fx=camera_params['f'][0],
                                  fy=camera_params['f'][1],
                                  cx=camera_params['c'][0],
                                  cy=camera_params['c'][1],
                                  znear=frustum_['near'],
                                  zfar=frustum_['far'])

P = camera.get_projection_matrix(size,size)
V = np.linalg.inv(pose_mat)
M = np.eye(4)
Vw= viewport(0,0,size,size)

landmarks_expanded = np.ones((68,4)) 
landmarks_expanded[:68,:3] = landmarks

expanded = (Vw@P@V@landmarks_expanded.T).T
plt.scatter([expanded[:,0]],[expanded[:,1]])
plt.show()
plt.scatter([landmarks[:,0]],[landmarks[:,1]])
plt.show()

`
But the resulting image is a bit skewed.
I'm probably doing something wrong... but not sure what.
Any help would be greatly appreciated!