The geometric transformations of the plane or space most commonly considered generally preserve collinearity: the images of three collinear points are themselves collinear. This is true of rotations and translations, but also of orthogonal projections onto a line or a plane.
These transformations also preserve ratios of lengths: if one of two line segments on the same line D is twice as long as the other, the same is true of their images on the line D’, the image of D.
The translation by vector u preserves the collinearity of points A, B and C, as well as the relative position of B within the line segment [AC].
The artists’ contribution
---------------------