Perspective Ruler

prusaprinters

A tool for finding vanishing points along a horizon line. One of the important theorems of linear perspective is that the image of any line not parallel to the picture plane will converge at the same point as all other lines which have the same angle to the picture plane. The vanishing point is the point at which all lines that are 90° to the picture plane converge. The distance points are the points at which all lines that are 45° from the picture point converge, either to the left or to the right. The distance points also define the position of the ideal observer. If we wish for the image to project accurately, our observer should position their single immobile eye perpendicular to the picture plane, in front of the vanishing point, at a distance equal to the distance between the vanishing point and the distance point. How, then, can do we project lines at angles other than 90° or 45° from the vanishing point?This tool is one way, though not the best way (in fact, using the same method, some manner of perspectival calipers would be adaptable to different distances; but since I am making this for a template contest, not a caliper contest you'll have to bear with the rigidity of this instrument :) ). This ruler marks off points along an imagined horizon where the images of the lines of the given angles would converge. Admittedly this ruler will only work for very small pictures (a set of calipers maintaining identical proportions to this ruler would have the advantage of being able to encompass constructions with different distances.). Ideally the 45° points should be left beyond the boundaries of the image. To draw the image of a 90° angle (as in the corner of a box) we will find one point on each half of the picture point. The sum of the angles of these two points should equal 90°. For instance, if I mark off the 65° point at the left side of the picture plane, on the right side I should mark off 25°. Please let me know if you have any questions; maybe eventually I can draw some diagrams to help illustrate this method.