
RogCAD home back to RogCAD history Original notes and derivations for RogCAD, April 1993 preCAD planning sketch The first nine images below are of the non generalized derivation (predefined perspective point and focal point) of the floating image plane and projection of a structure. The second batch of nine images is of the generalized derivation (variable perspective point and focal point) which is much more complicated. Vector crossproduct is used to create a floating image plane with a normal vector that passes through the origin of the xyz axes. Points on the structure are projected onto the floating image plane. Vector dotproduct is used to test from which side of the zaxis each projected point stems. After the initial vector considerations, it's just algebra  nothing we didn't do in high school. But the magic of algebra fascinates me, especially when it goes on for many pages and the darn thing actually works. Those derivations produced the original program code for a specific perspective point and focal point: The program printout on the dotmatrix printer: The first RogCAD output. The points had to be plotted on paper: Derivation of floating image plane and projection of structure, generalized, next nine images: back to RogCAD history RogCAD home 
