### 11 Locus lines

If you trace a point that depends on a point on a linear object you do not get a surface, as the
movement is only one-dimensional, but a curve.

You can construct conic sections this way:

The cone itself was constructed as a locus-surface (by constructing a line, a point on that line
and a circle with this point as midpoint and a vector from the midpoint to another point on the
cone as radius).

The conic section is constructed as follows:

- construct a circle around the cone
- construct a point on that circle
- construct a line through this point and the cone’s tip
- if you intersect the line with a plane and then trace the intersection in dependency of
the point on the circle, you get the conic section.