Georges Lemmen, The Beach at Heist, c. 1891/2, 
Musée d'Orsay Paris

<-- Pointillism,  also known as Divisionism, is a technique of painting in which small distinct dots of varying colours are applied to a medium, and the pattern from these dots forms an image. As the tin dots become blended in the viewer's eye. The technique was developed in 1886 by Georges Seurat and Paul Signac. The technique is a branch of Impressionism and many of the proponents were involved in the Impressionist movement. Other terms which are used in reference to this technique are Divisionism and Neo-Impressionism. The term Pointillism was initially derogatory and used by art critics in 1880s to ridicule works of art which employed this technique.

The Papal Palace, Avignon, oil on canvas, 1900, Musée d'Orsay, Paris

Leonardo Da Vinci's - The Last Supper
Click to enlarge

 A simplistic view of the horizon line in art, is to consider it as your 'eye-level line'. The horizon line in art is a perspectival line. In the real world, the horizon line is where the sky meets the sea. However in a fictive space, that is a painting's perspective, it is the level of the viewer's eye in relation to the scene of the painting. The horizon line is an imaginary line to which all converging lines recede (in other words where all things recede). The horizon line is an important part of a painting's compositional arrangement, it is important in arranging a realistic scene and the line needs to be straight as the artist then applies perspective rules to objects within the painting in relation to this line.

Top tip:
Horizon line can be regarded as your eye-level line, the level which you are intended to view the painting at, and for an accurate rendition of recession within the painting.

Leonardo Da Vinci's - The Last Supper
with illustrated horizon line
Click to enlarge

A painting's viewpoint is the height from which the viewer and/or painter sees the subject. The viewpoint is crucial as it determines where the horizon line is within the painting. The creation of a consistent and continuous horizon line is fundamental in imbuing a painting with perspective. The artist defines the viewpoint for the viewer and in turn the viewpoint helps shape our conceptualization of the subject matter, for example in dictating the direction or elevation from which we view a scene within a painting. Thus giving precedence to particular areas of a canvas over others.

Also known as a viewer's vantage point into the fictive space; the concept of viewpoint is closely linked to perspective.

Gustave Courbet's - The Stone breakers 1849
The viewpoint is level with the scene in the foreground,
the painting has a low perspective which accelerates
our view into the background.