The text explains the concept of "Accidental Points" in perspective drawing. These points occur when objects are positioned in unusual or varying angles relative to the horizon line, affecting how imaginary lines converge. It describes how different orientations of straight-lined figures influence the location of these accidental convergence points.
This new type of convergence points is designated as Accidental Points.
When the object is on a horizontal plane, the accidental points are more or less distant, but always on the eye's horizon line, where the viewpoint is, which can also be called the viewpoint line.
If the object, instead of being on a horizontal plane, is in a more or less inclined or oblique position relative to the horizon plane, the accidental points may be found higher or lower, depending on the object's position.
It is conceived that the ornamentation strips that could be found on the face BFEA, parallel to AE, BF, would converge at the accidental point P; those on the face BADC, parallel to AD, BC, would converge at point H. Regarding the face above the box AEGD, the strips parallel to the sides AE, DG, would converge at P, and those parallel to the sides AD, EG would converge at H.
The viewpoint exists likewise in the current example (fig. 12), but none of the vanishing lines of the box being parallel to the observer, these lines will not converge at the viewpoint.
All figures composed of straight lines, of which one side is not parallel to the observer, have one or more accidental points, which then serve as convergence points for the vanishing lines of these figures.
Translation Notes:
Accidental Points: These refer to points in perspective drawing where imaginary lines converge at unexpected or non-standard locations relative to the observer's standard viewpoint.
Convergence Points: These are often used in drawing to help establish depth and perspective.