artist's impression vs computer graphics

artist's impression

noun
  • A sketch or drawing of someone or something, produced when it is not possible to take a photograph. 

computer graphics

noun
  • The representation and manipulation of pictorial data by a computer. 

  • The various technologies used to create and manipulate such pictorial data. 

  • A sub-field of computer science which studies methods for digitally synthesizing and manipulating visual content. 

  • The images so produced. 

How often have the words artist's impression and computer graphics occurred in a corpus of books? (source: Google Ngram Viewer )