Which two general classes do picture drawings fall into?

Picture drawings typically fall into the classes of perspective and isometric.

Perspective drawings depict objects as they appear to the human eye, showing depth and relative size based on their position in space. This technique captures how an object would look in three dimensions, providing a more realistic and visually appealing representation. This is beneficial for imaginative visualization of designs.

Isometric drawings, on the other hand, allow for an object to be represented in three dimensions on a two-dimensional plane. They use specific angles to illustrate the object's width, depth, and height without distortion in perspective. Isometric views are particularly useful in technical and engineering drawings where accurate measurement and understanding of spatial relationships are critical.

Combining these two drawing types allows for a comprehensive visual understanding of an object, leveraging both realistic depiction and technical accuracy.