Three words that can describe irregular line are

I’m pretty sure they are described as loose, wild and chaotic

These traits are all equally important in recognizing the validity of artwork mainly due to an artists' consistent style and reputation which they have developed over a lengthy period of time. most famous paintings contain specific characteristics of the artist who created it. an appraiser would pay close attention to certain key elements within the painting, as well as an accuracy in measurement and color shade. blended textures and outlines are essential in recognizing an authentic piece from a copy. signature and imagery exist in epic proportions to balance out each trait as they coexist in harmony, depending on preference and style of each artist. no two original pieces are virtually identical, although it may be almost impossible to see discrepancy with the naked eye.

Perspective is important because it enabled the 3 dimensional world to be translated into the 2d world of the picture plane. this had an immediate impact on the representation of reality in art and design.