Tidy + improve mesh-from-numbers bonues example.

Author: pp-mo

notebooks/.notebook_shadow_copies/mesh_from_numbers.md

@@ -12,15 +12,12 @@ jupyter:
     name: python3
 ---
 
-```python
-
-```
-
-## Constructing an Iris mesh from bare numbers
+# Constructing an Iris mesh from bare numbers
 
 ```python
-# Construct a test mesh from scratch ??
+# Construct a test mesh from scratch : define a mesh in numbers
 
+# define some node X and Y points
 import numpy as np
 big_points_x = np.array([6.0, 3, 5, 1, 5, 3, 5, 5, 4, 2, 1, 6, 3, 5, 3, 6, 2, 6, 1, 2, 2, 4, 1, 4, 4, 3, 4, 6, 2, 1])
 big_points_y = np.array([2.5, 1, 3, 0, 2, 0, 0, 4, 3.5, 2.5, 1, 4.5, 4, 1, 3, 3.5, 0.5, 0.5, 3, 4.5, 1.5, 2.5, 4, 1.5, 4.5, 2, 0.5, 1.5, 3.5, 2])
@@ -29,6 +26,7 @@ big_points = np.stack([big_points_x, big_points_y]).T
 
 big_data = 100 * np.random.rand(30)
 
+# define which faces use which points
 big_faces = [
     [22, 28, 19],
     [18, 28, 22],
@@ -59,16 +57,21 @@ for face in big_faces:
     big_face_plottable_x[-1].append(big_points_x[face[0]])
     big_face_plottable_y[-1].append(big_points_y[face[0]])
 
-# Find coordinates in the middle of the faces
-
+    
+# Calculate coordinates of locations in the "middle" of each face
+# N.B. except, means of lats + lons are not true centres !
 face_coordinates_x = [np.mean(xs) for xs in big_face_plottable_x]
 face_coordinates_y = [np.mean(ys) for ys in big_face_plottable_y]
 
-big_face_data = np.random.rand(face_count)
+# Calculate some random data for the cube 'payload'.
+np.random.seed(seed=1234)
+big_face_data = np.random.uniform(0, 100, face_count)
 ```
 
 ```python
-### We know about this stuff
+# Create the component coordinates and connectivities.
+
+import iris.experimental.ugrid
 from iris.coords import AuxCoord
 
 # node coordinates
@@ -91,7 +94,8 @@ face_coords_and_axes = [
 ```
 
 ```python
-# I'll be shocked if you ever make a mesh like this
+# Make a mesh by passing the coordinates + connectivities
+# N.B. it's pretty unusual to be calling this directly, but the API does exist
 
 from iris.experimental.ugrid.mesh import Mesh
 
@@ -106,7 +110,8 @@ print(my_first_mesh)
 
 ```python
 # Here we make a cube with data attached to **faces**
-# (one mesh can be attached to different cubes, with those cubes using the same or different locations)
+# N.B. a mesh may be shared by multiple cubes, the cubes may use the same or different locations
+
 from iris.cube import Cube
 
 x_coord = iris.experimental.ugrid.mesh.MeshCoord(my_first_mesh, "face", "x")
@@ -122,3 +127,15 @@ my_first_mesh_cube = iris.cube.Cube(
 
 my_first_mesh_cube
 ```
+
+```python
+# Assign some data to the cube, convert to a PolyData and plot it
+
+from pv_conversions import pv_from_lfric_cube
+pv = pv_from_lfric_cube(my_first_mesh_cube)
+pv.plot(jupyter_backend='static')
+```
+
+```python
+
+```