Final answer:
Pictorials like isometric or oblique sketches provide a three-dimensional view on a two-dimensional plane, simplifying visualization of the whole object or scene. They help highlight important details, overcome photographic limitations in fieldwork, and use artistic techniques such as linear and atmospheric perspective to convey depth and realism.
Step-by-step explanation:
Pictorials such as Isometric or Oblique sketches are used instead of Orthographic drawings for several reasons. They provide a unique visual perspective that can convey multiple dimensions in a single view, offering a more holistic understanding of a structure or object. Unlike orthographic drawings that require multiple views to represent all facets of an object, isometric and oblique sketches present a three-dimensional representation on a two-dimensional surface, making it easier to visualize the item as a whole.
For geologists, for example, sketches allow the observer to focus on important details, excluding irrelevant background elements. They provide the flexibility to use shading and colors to highlight specific aspects and facilitate on-the-spot annotations, crucial for fieldwork where accessibility to technology may be limited. These sketches also overcome challenges such as bad lighting, obscured views, or the need to capture extensive landscapes or focus on detailed areas which could be difficult with photography.
In art, different perspectives like linear and atmospheric perspective have been traditionally used to add depth and realism. Linear perspective uses orthogonal lines converging at a vanishing point, creating the illusion that objects are receding into the distance, while atmospheric perspective involves the use of color and clarity to depict depth, as distant objects appear grayer, bluer, and less distinct due to haze and water vapor in the air. These methods, along with scale and proportion changes, help to convey a sense of time and motion in static images.