曲线滑动：等边三角形截面

GeoGebra 命令及参数

1. PointIn(y > 0) → A
2. PointIn(y > 0) → B
3. PointIn(y > 0) → C
4. PointIn(y > 0) → D
5. PointIn(y > 0) → E
6. FitPoly({A, B, C, D, E}, n) → f
7. Rotate(If[Min[l1] ≤ x ≤ Max[l1], f(x)], π / 2, xAxis) → h_1
8. Point(h_1) → F
9. Rotate(G, π / 2, xAxis) → G'
10. Plane(G, G + (0, 1, 0), G + (0, 0, 1)) → p
11. Segment(G', H) → g
12. Surface(u, (-ra) + ((2 * ra) * v), f(u), u, Min[l1], Max[l1], v, 0, 1) → d
13. CurveCartesian(u, 0, f(u) + (sqrt(3) * ra), u, Min[l1], Max[l1]) → e
14. Surface(u, (-ra) + (ra * v), f(u) + ((sqrt(3) * ra) * v), u, Min[l1], Max[l1], v, 0, 1) → i
15. Surface(u, (ra * v), (((-sqrt(3)) * ra) * v) + f(u) + (sqrt(3) * ra), u, Min[l1], Max[l1], v, 0, 1) → j
16. Mirror(H, G') → H'
17. Segment(H, H') → k
18. Rotate(H, If[0 < MoveMeFirst ≤ 1, (MoveMeFirst * π / 3), π / 3], H', Plane[I, H', H]) → H'_1
19. Rotate(H', If[0 < MoveMeFirst ≤ 1, (MoveMeFirst * π / 3), π / 3], H', Plane[I, H', H]) → H''
20. Segment(H'_1, H'') → k'
21. Rotate(H', If[1 < MoveMeFirst ≤ 2, ((-(MoveMeFirst - 1)) * π / 3), ((-π)) / 3], H, Plane[I, H', H]) → H''_1
22. Segment(H''_1, H) → l
23. Polygon(H, H', Rotate[H, ((-π)) / 3, H', Plane[H, H', I]]) → t1, m, h_2, h'
24. CurveCartesian(u, ra, f(u), u, Min[l1], Max[l1]) → b
25. CurveCartesian(u, (-ra), f(u), u, Min[l1], Max[l1]) → c
26. Segment(M, J) → q
27. Segment(J, N) → r
28. Segment(N, M) → s
29. Segment(K, O) → t
30. Segment(O, L) → a
31. Segment(L, K) → f_1