Distance circle
The distance circle of a central projection is the circle with the center in the main point , which has the distance as a radius. The radius of the distance circle is therefore equal to the distance of the viewing eye from the image plane . The distance circle can be imagined as the intersection of a cone with half an opening angle of 45 ° with the tip at the eye point and the perpendicular from the eye point to the image plane as the axis. The distance circle is thus the entirety of the vanishing points of straight lines that intersect the panel at an angle of 45 °. Such vanishing points play an important role in the application of true lengths to contour lines (see architect arrangement and frontal perspective ) and are called distance points . The area that the distance circle limits corresponds to the area that a camera (lens at the eye point, main point is the center of the image) with a wide-angle lens with a focal length of 20 mm (a "normal" focal length is 35 mm).
See also
literature
- The distance circle (PDF; 24 kB) Institute for Analysis and Algebra at the TU Braunschweig
- Diagram design (PDF; 15.7 MB) Institute for Representation and Design at the University of Stuttgart
- Cornelie Leopold: Geometric Basics of Architectural Representation. Verlag W. Kohlhammer, Stuttgart, 2005, ISBN 3-17-018489-X , p. 233