+ z0 = (hround_pixels (xpart origin), 0);
+
+ z1 = z1' = z0 + llap * dir (90 + tilt) xscaled xs;
+ z2 = z2' = z0 + llap * dir (90 + tilt + 120) xscaled xs;
+ z3 = z3' = z0 + llap * dir (90 + tilt + 240) xscaled xs;
+
+ z12 = caveness [.5[z1, z2], z3];
+ z23 = caveness [.5[z2, z3], z1];
+ z31 = caveness [.5[z3, z1], z2];
+
+ triangle_a = z1 .. z12 .. z2;
+ triangle_b = z2 .. z23 .. z3;
+ triangle_c = z3 .. z31 .. z1;
+
+ penposx1 (angle (direction 0 of triangle_a) - 90);
+ penposx2 (angle (direction 0 of triangle_b) - 90);
+ penposx3 (angle (direction 0 of triangle_c) - 90);
+
+ penposx1' (angle (direction infinity of triangle_c) + 90);
+ penposx2' (angle (direction infinity of triangle_a) + 90);
+ penposx3' (angle (direction infinity of triangle_b) + 90);
+
+ penposx12 (angle (z12 - z0));
+ penposx23 (angle (z23 - z0));
+ penposx31 (angle (z31 - z0));
+
+ z10 = (z0 -- z1) intersectionpoint (z1l .. z12l .. z2'r);
+ z20 = (z0 -- z2) intersectionpoint (z2l .. z23l .. z3'r);
+ z30 = (z0 -- z3) intersectionpoint (z3l .. z31l .. z1'r);
+
+ triangle_in = z10
+ .. z12l
+ .. z20
+ & z20
+ .. z23l
+ .. z30
+ & z30
+ .. z31l
+ .. z10
+ & cycle;
+
+ triangle_out_a = z1r .. z12r .. z2'l;
+ triangle_out_b = z2r .. z23r .. z3'l;
+ triangle_out_c = z3r .. z31r .. z1'l;
+
+ triangle_out = top z1
+ .. lft z1
+ .. z1r{direction 0 of triangle_out_a}
+ & triangle_out_a
+ & {direction infinity of triangle_out_a}z2'l
+ .. lft z2
+ .. bot z2
+ .. z2r{direction 0 of triangle_out_b}
+ & triangle_out_b
+ & {direction infinity of triangle_out_b}z3'l
+ .. rt z3
+ .. top z3
+ .. z3r{direction 0 of triangle_out_c}
+ & triangle_out_c
+ & {direction infinity of triangle_out_c}z1'l
+ .. cycle;
+
+
+ labels (0, 10, 20, 30);
+ penlabels (1, 1', 2, 2', 3, 3', 12, 23, 31);