AERIAL OBLIQUE PERSPECTIVE (3 VANISHING POINTS)
The process is identical to that of the aerial parallel perspective.
Sketch the horizon line and the measurement line. The distance between these two lines is the height at which the viewer is standing.
Locate the third point. From the center of the square remade in three dimensions, by the median line, calculate the distance the viewer is placed. This third point is called view point.
The vanishing points 1 and 2 and the depth point are found with lines parallel to the square leaned on the measurement line leaving from the view point. See lines A, B and C in the graph.
Two imaginary lines of measurement that do not run from the third point are necessary to find the height. One is located on the front near the edge and view point lines. The other is the lateral vertical line.
See points 1, 2, 3 and 4 in the graph, showing the transfers of measurement to the front edge in perspective.
The measurement calculated from point 1 is the measurement in perspective in point 4.
The out-of-focus vision is located in the view point and the vision focused in the square located on the measurement line. In this type of perspective the eyes focus the image in the so called accommodation range.