Implicitization

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Implicitization experiments on curves and surfaces

These are some experimental results of the algorithms that compute the Newton polytope of the Resultant. For more information see [1].

For the case of curves, there are two equations on one variable t. For the case of surfaces, there are three equations on two variables t,s. Additionally, a,b,c are constants.

Each parametric equation can be transformed to a polynomial. The supports of the polynomials after the Cayley trick are stored in the files in the "supports" column. The file format is as follows: the first line contain the number of points and their dimension and in the following lines each column contains the coordinates of a point.

Implicitization using predicted support has been implemented in Maple. In our experiments we use two support prediction methods: one applies only for curves, and another is general. We present our implementation of the "curves only" method and some examples. Here we apply numeric as well as exact methods for linear solving in order to obtain coefficients of the implicit equation.

Another Maple implementation contains two implicitization methods for general support prediction that use exact solving. Examples of running these methods on the curves and surfaces.

For more information see [2].

Support prediction

Curves

No curve [3] parametric equation supports # mixed subdivisions

Enum by reverse search (sec) [4]

TOPCOM point2alltriang (sec) [5]

TOPCOM point2triang(sec) [6]

# mixed cell configurations # N(R) vertices N(R) vertices # all lattice points of N(R) implicit polytope's terms & coefficients implicit support prediction (for curves)
1. astroid a\cos(t)^3,a\sin(t)^3

supports

289 193.62 0.048 0.452 289 35 N(R) 454 implicit support
2. cardioid $a(2\cos(t)-\cos(2t)),a(2\sin(t)-\sin(2t))$

supports

37 6.52 0.005 0.024 37 10 N(R) 33 implicit support
3. circle $ \cos(t),\sin(t)$

supports

5 0.004 0.016 0.004 5 3 N(R) 4 implicit support
4. conchoid $a+\cos(t),a\tan(t)+\sin(t)$

supports

12 0.84 0.003 0.008 12 4 N(R) 6 implicit support
5. ellipse $a\cos(t),b\sin(t)$

supports

5 0.15 0.001 0.004 5 3 N(R) 4 implicit support
6. folium of Descartes $3at/(1+t^3),3at^2/(1+t^3)$

supports

14 0.94 0.004 0.008 14 6 N(R) 10 implicit support
7. involute of a circle $a(\cos(t) t(\sin(t)),a(\sin(t)-t\cos(t))$

supports

14 1.00 0.001 0.007 14 6 N(R) 7 implicit
8. nephroid $a(3\cos(t)-\cos(3t)),a(3\sin(t)-\sin(3t))$

supports

289 195.27 0.004 0.240 289 35 N(R) 454 implicit support
9a. Plateau curve $a\sin(3t)/\sin(t),2a\sin(2t)$

supports

94 33.02 0.012 0.064 94 15 N(R) 55 implicit
9b. plateau curve $a\sin(6t)/ \sin(2t), 2a\sin(4t)$

supports

42168 halt 25.934 85.597 42168 495 N(R) not computed implicit
10. talbot's curve $(a^2 + c^2 \sin( t)^2) \cos( t)/a, (a^2 - 2c^2 + c^2\sin(t)^2)\sin(t)/b $

supports

1944 3948.80 0.416 2.356 1944 84 N(R) 1600 implicit
11. tricuspoid $a(2\cos(t)+\cos(2t)),a(2\sin(t)-\sin(2t))$

supports

37 6.20 0.008 0.024 37 10 N(R) 33 implicit support
12. witch of Agnesi $at,a/(1 + t^2)$

supports

2 0.03 0.007 0.004 2 2 N(R) 2 implicit
13. circle (3 systems) $(-t^2 +1)/s, 2t/s, t^2 -s +1$

supports

26 6.00 0.020 0.052 26 6 N(R) 7 implicit
14. A' Campo curve $9ts-4,t^3+s^2+c1,t^2+s^3+c2$

supports

29 - - - 29 6 N(R) 18 implicit

Surfaces

No surface parametric equation supports # mixed subdivisions

Enum by reverse search (sec)

TOPCOM point2alltriang (sec)

TOPCOM point2triang(sec)

# mixed cell configurations # N(R) vertices N(R) vertices # all lattice points of N(R) implicit polytope's terms & coefficients
1. cylinder $\cos(t),\sin(t),s$

supports

5 0.24 0.003 0.006 5 3 N(R) 4 implicit
2. cone $s\cos(t),s\sin(t),s$

supports

122 73.45 0.192 0.288 98 8 N(R) 14 implicit
3. paraboloid $s\cos(t),s\sin(t),s^2$

supports

122 71.60 0.192 0.296 98 8 N(R) 37 implicit
4. surface of revolution $s\cos(t),s\sin(t),\cos(s)$

supports

122 71.80 0.193 0.288 98 8 N(R) 37 implicit
5. sphere $\sin(t)\cos(s),\sin(t)\sin(s),\cos(t)$

supports

104148 halt 19496.602 714.161 43018 21 N(R) 186 implicit
6. sphere2 $\cos(t)\cos(s),\sin(t)\cos(s),\sin(s)$

supports

76280 halt 4492.977 397.157 32076 95 N(R) 776 implicit
7. stereographic sphere $2t/(1 t^2 s^2),2s/(1 t^2 s^2),(t^2 s^2-1)/(1 t^2 s^2)$

supports

3540 7112.54 25.402 11.025 3126 22 N(R) 283 implicit
8. twisted sphere $a(\cos(t) t(\sin(t)),a(\sin(t)-t\cos(t))$

supports

>1812221 not computed not computed not computed not computed not computed not computed implicit

Implicitization

These results have been obtained using Maple 11 exact solving methods.

Curves

No curve parametric degree parametric terms "curves only" matrix size

"curves only" method runtime (sec)

generic method: matrix size

generic method runtime (sec)

generic method nonzero coeffs "mapping" method: matrix size

"mapping" method runtime (sec)

"mapping" method nonzero coeffs (actual coeffs) implicit degree
1. cardioid 4, 4 3, 4 15 0.128 33 0.248 33 25 0.656 7 4
2. conhoid 2, 3 2, 4 15 0.094 6 0.096 6 15 0.308 6 4
3. folium of descartes 3, 3 3, 3 10 0.092 5 0.032 3 11 0.144 3 3
4. nephroid 4, 4 4, 5 28 0.256 426 not computed not computed 49 5.452 10 6
5. ranunculoid 12, 12 7, 12 91 8809.43 not computed not computed not computed not computed not computed not computed not computed
6. talbot's curve 6, 6 3, 4 28 109.342 421 not computed not computed not computed not computed 23 6
7. tricuspoid 4, 4 3, 4 15 0.216 33 0.236 33 25 0.540 8 4
8. whitch of agnesi 1, 2 2, 2 4 0.016 2 0.044 2 4 0.048 3 3


Surfaces

No surface parametric degree parametric terms # inside points generic method: matrix size

generic method runtime (sec)

generic method nonzero coeffs "mapping" method: matrix size

"mapping" method runtime (sec)

"mapping" method nonzero coeffs (actual coeffs) implicit degree
1. Infinite cylinder 2, 2, 1 2, 3, 2 4 4 0.036 4 9 0.072 3 2
2. Hyperbolic paraboloid 1, 1, 2 2, 2, 3 3 3 0.028 3 7 0.064 3 2
3. Infinite cone 3, 2, 1 4, 3, 2 14 8 0.040 6 19 0.224 3 4
4. Whitney umbrella 2, 1, 2 2, 2, 2 2 2 0.024 2 4 0.056 2 3
5. Monkey saddle 1, 1, 3 2, 2, 3 3 3 0.028 3 8 0.064 3 3
6. Handkerchief surface 1, 1, 3 2, 2, 5 2 2 0.020 2 4 0.036 5 3
7. Crossed surface 1, 1, 4 2, 2, 2 5 5 0.032 5 10 0.072 2 4
8. Quartoid 1, 1, 4 2, 2, 4 4 4 0.012 4 16 0.140 4 4
9. Peano surface 1, 1, 4 2, 2, 4 4 4 0.020 4 10 0.080 4 4
10. Bohemian dome 2, 4, 2 2, 6, 3 142 58 2.764 error 125 83.362 7 4
11. Swallowtail surface 4, 3, 1 3, 3, 2 12 12 0.052 12 25 0.432 6 5
12. Sine surface 2, 2, 4 3, 3, 8 1027 87 9.244 66 125 107.102 7 6
13. Enneper's surface 3, 3, 2 4, 3, 3 439 258 74.304 258 106 33.562 57 9

Remarks

[1] Fisikopoulos Vissarion, Triangulations of point sets, high dimensional Polytopes and Applications, Master thesis, University of Athens, Graduate Program in Logic, Algorithms and Computation, 2010 [1]

[2] I. Z. Emiris, T. Kalinka, Ch. Konaxis, Implicitization of curves and surfaces using predicted support, 2011 [2]

[3] Many thanks to Tatjana Kalinka for providing this list of curves and surfaces.

[4] This is the computation time of enumeration of regular triangulations algorithm using reverse search. I would like to thank very much Fumihiko TAKEUCHI for running the experiments and providing this results. Experiments were done on a Blade 100, 550Mhz, 2GB memory with SunOS 5.9.

[5] This is the computation time of points2alltriangs client of TOPCOM package. Experiments were done on a Intel(R) Pentium(R) 4 CPU 3.20GHz, 1.5GB memory with x86_64 Debian GNU/Linux.

[6] This is the computation time of points2triangs client of TOPCOM package. Experiments were done on a Intel(R) Pentium(R) 4 CPU 3.20GHz, 1.5GB memory with x86_64 Debian GNU/Linux.

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