### Alignment with an Axis

 Transform align_with_axis (Point p0, Point p1, [char axis = 'z']) Function
 Returns the `Transform` that would align the line through p0 and p1 with the major axis denoted by the axis argument. The default is the z-axis. This function is used in the functions that find intersections. ``` Point P0(1, 1, 1); Point P1(2, 3, 4); P0.draw(P1); P0.dotlabel("\$P_0\$"); P1.dotlabel("\$P_1\$"); Transform t; t.align_with_axis(P0, P1, 'z'); P0 *= P1 *= t; t.show("t:"); -| t: 0.949 -0.169 0.267 0 0 0.845 0.535 0 -0.316 -0.507 0.802 0 -0.632 -0.169 -1.6 1 P0.show("P0:"); -| P0: (0, 0, 0) P1.show("P1:"); -| P1: (0, 0, 3.74) ``` The following example shows how `align_with_axis()` can be used for putting plane figures into a major plane. ``` default_focus.set(2, 3, -10, 2, 3, 10, 10); Circle c(origin, 3, 75, 25, 6); c.shift(2, 3); c.draw(); Point n = c.get_normal(); n.shift(c.get_center()); Transform t; t.align_with_axis(c.get_center(), n, 'y'); t.show("t:"); -| t: 0.686 0.379 -0.621 0 0.543 0.3 0.784 0 0.483 -0.875 0 0 -3 -1.66 -1.11 1 n *= c *= t; c.draw(); c.show("c:"); -| c: fill_draw_value == 0 (1.31, 0, -0.728) .. (1.49, 0, -0.171) .. (1.44, 0, 0.413) .. (1.17, 0, 0.933) .. (0.728, 0, 1.31) .. (0.171, 0, 1.49) .. (-0.413, 0, 1.44) .. (-0.933, 0, 1.17) .. (-1.31, 0, 0.728) .. (-1.49, 0, 0.171) .. (-1.44, 0, -0.413) .. (-1.17, 0, -0.933) .. (-0.728, 0, -1.31) .. (-0.171, 0, -1.49) .. (0.413, 0, -1.44) .. (0.933, 0, -1.17) .. cycle; n.show("n:"); -| n: (0, 1, 0) ``` Fig. 75.