As suggested by @Mat1629, this PR adds two new shapes to create lines. This can be convenient for, e.g., defining 3D ASI structures.

Line(x1, y1, z1, x2, y2, z2, diam, linecap) generates a line from $(x_1, y_1, z_1)$ to $(x_2, y_2, z_2)$ with a diameter diam. The behavior of the line at these two endpoints is determined by the last argument linecap, which can be

• "infinite": the line extends indefinitely beyond the two specified points.
• "round": a sphere of radius diam is placed at the two endpoints, yielding a smooth shape.
• "flat": the line stops abruptly at the two endpoints in a flat plane perpendicular to the line.

Line2D(x1, y1, x2, y2, diam, linecap) behaves the same, but extends indefinitely along the Z-axis. Hence, this basically creates a plane in 3D space whose normal vector always lies in the XY-plane.

A special case was implemented for diam=0, in which case the shape will be a minimally connected geometry of all cells intersected by the line.

Visual examples

Below are some geometries from test/line.mx3 (but after an additional relax()).

	Line	Line2D
"round"
"flat"
"infinite"
"infinite" with diam=0