Affine transformations are a way to represent movement, scaling and rotation of objects. They're based on homogeneous co-ordinates.
The spheres have one of two types of transformation applied to them:
The camera is also positioned using affine transformations. We should never need to scale the camera, but we do rotate it around each of the three axis to make sure we have the code right.
The code is at Scenes/early/affine-transformations.cpp.