There is a thing called "Perceptual diff", so I would call it "perceptual".
In order to ensure that code changes do not change the look of previously rendered scenes, the renderer, utilities and shaders are tested by an automated batch process every night. ... A reference frame would be rendered and stored as a canonical image. Then, when any code changes, the new version of the renderer would used to render the scene and the resulting image compared against the canonical. ... This would produce images that are not pixel identical to the canonical but nevertheless correct. The perceptual metric allows us to make such code changes without breaking the automated testing process.