Lay out And Two-point perspective drawing

Layout
Measuring the dimensions of a subject while blocking in the drawing is an important step in producing a realistic rendition of the subject. Tools such as a compass can be used to measure the angles of different sides. These angles can be reproduced on the drawing surface and then rechecked to make sure they are accurate. Another form of measurement is to compare the relative sizes of different parts of the subject with each other. A finger placed at a point along the drawing implement can be used to compare that dimension with other parts of the image. A ruler can be used both as a straightedge and a device to compute proportions.
When attempting to draw a complicated shape such as a human figure, it is helpful at first to represent the form with a set of primitive shapes. Almost any form can be represented by some combination of the cube, sphere, cylinder, and cone. Once these basic shapes have been assembled into a likeness, then the drawing can be refined into a more accurate and polished form. The lines of the primitive shapes are removed and replaced by the final likeness. Drawing the underlying construction is a fundamental skill for representational art and is taught in many books and schools, as its correct application will resolve most uncertainties about smaller details and make the final image look self-consistent.
A more refined art of figure drawing relies upon the artist possessing a deep understanding of anatomy and the human proportions. A trained artist is familiar with the skeleton structure, joint location, muscle placement, tendon movement, and how the different parts work together during movement. This allows the artist to render more natural poses that do not appear artificially stiff. The artist is also familiar with how the proportions vary depending on the age of the subject, particularly when drawing a portrait.
[edit] Perspective
Linear perspective is a method of portraying objects on a flat surface so that the dimensions shrink with distance. The parallel, straight edges of any object, whether a building or a table, will follow lines that eventually converge at infinity. Typically this point of convergence will be along the horizon, as buildings are built level with the flat surface. When multiple structures are aligned with each other, such as buildings along a street, the horizontal tops and bottoms of the structures will all typically converge at a vanishing point.


Two-point perspective drawing.
When both the fronts and sides of a building are drawn, then the parallel lines forming a side converge at a second point along the horizon (which may be off the drawing paper.) This is a "two-point perspective". Converging the vertical lines to a point in the sky then produces a "three-point perspective".
Depth can also be portrayed by several techniques in addition to the perspective approach above. Objects of similar size should appear ever smaller the further they are from the viewer. Thus the back wheel of a cart will appear slightly smaller than the front wheel. Depth can be portrayed through the use of texture. As the texture of an object gets further away it becomes more compressed and busy, taking on an entirely different character than if it was close. Depth can also be portrayed by reducing the amount of contrast of more distant objects, and also by making the colors more pale. This will reproduce the effect of atmospheric haze, and cause the eye to focus primarily on objects drawn in the foreground.