CreateTransform:
PROC [
cellSize: CD.Position,
cellInstOrient: CD.Orientation,
cellInstPos: CD.Position ← [0,0]]
RETURNS [Imager.Transformation];
-- Given the size of a cell,
-- the position and orientation of an instance of that cell in "world"
-- co-ordinates, returns the transformation to be applied to
-- cell points to get world points.