Node: Paths, Next: , Previous: Drawing and Labeling Points, Up: Top


Points alone are not enough for making useful drawings. The next step is to combine them into Paths, which are similar to Metafont's paths, except that they are three-dimensional. A Path consists of a number of Points and strings representing the connectors. The latter are not processed by 3DLDF, but are passed unchanged to the output file. They must be valid connectors for MetaPost, e.g.:

     {dir 60}..
     {z1 - z2}..
     .. tension 1 and 1.5..
     ..controls z1 and z2..

Usually, it will only make sense to use .. or -, and not ..., --, tension, curl, controls, or any of the other possibilities, in Paths, unless you are sure that they will only be viewed with no foreshortening due to the perspective projection. This can be the case, when a Path lies in a plane parallel to one of the major planes, and is projected using parallel projection onto that plane. Otherwise, the result of using these connectors is likely to be unsatisfactory, because MetaPost performs its calculations based purely on the two-dimensional values of the points in the perspective projection. While the Points on the Path will be projected correctly, the course of the Path between these Points is likely to differ, depending on the values of the Focus used (see Focuses), so that different views of the same Path may well be mutually inconsistent. This problem doesn't arise with "-", since the perspective projection does not "unstraighten" straight lines, but it does with "..", even without tension, curl, or controls. The solution is to use enough Points, since a greater number of Points on a Path tends to reduce the number of possible courses through the Points.1


  1. I believe that counter-examples could probably constructed, but for the most common cases, the principle applies.