Journal of Information & Computational Science 2: 2 (2005) 415–419 Available at http://www.joics.com Poisson Developable Surfaces ? Xingwang Zhang a,b , Guojin Wang a,b,∗ a Institute b State of Computer Images and Graphics, Zhejiang University, Hangzhou 310027, China Key Laboratory of CAD & CG, Zhejiang University, Hangzhou 310027, China Received 9 April 2005; revised 13 June 2005 Abstract Recurring to some excellent geometric and algebraic properties of Poisson curves, we present an algorithm that generates a developable Poisson surface through a Poisson curve of arbitrary degree. The technique is based on necessary and sufficient conditions for a developable surface, degree elevation formula of a Poisson curve and linear independence of Poisson basis. Some common transcendental surfaces are represented as Poisson developable surfaces accurately. Keywords: Poisson basis; Developable; Transcendental; Linear independence 1 Introduction Developable surfaces are a type of important and fundamental surfaces universally used in industry design [4]. Different methods have been presented for the design of developable surfaces [1, 2, 3, 6, 8]. Previous techniques can’t exactly represent a tangent surface or a cone through a helix frequently appearing in industry design. However, transcendental surfaces are frequently met in revolution cutting and are some important parts of the surfaces of milling cutters, helicoids and precision machinery parts. Noting that some common transcendental curves can be represented as Poisson curves, this paper introduces Poisson curves to the field of the design of developable surfaces, and successfully generates some developable transcendental surfaces. We represent some common transcendental surfaces as Poisson developable surfaces precisely. Then we approximate to the Poisson surfaces using the Poisson subdivision algorithm. The above results could be applied to the geometric configuration design and machining, as well as the plate expansion of spiral-like pipe surfaces. ? Supported by the National Grand Fundamental Research 973 Program of China (No. 2004CB719400), the National Natural Science Foundation of China (No. 60373033, No. 60333010) and the National Natural Science Foundation for Innovative Research Groups (No. 60021201). ∗ Corresponding author. Email address: wgj@math.zju.edu.cn (Guojin Wang). 1548–7741/ Copyright ° c 2005 Binary Information Press June 2005 416 X. Zhang et al. /Journal of Information & Computational Science 2: 2 (2005) 415–419 2 Properties of a Poisson Curve The parametric form of a degree n Poisson curve can be expressed as P(u) = ∞ X [n] bnk (u)pk , 0 ≤ u < R, (1) k=0 where (nu)k exp(−nu), k = 0, 1, · · · , (2) k! µm ¶+∞ P n [n] are degree n Poisson basis. The sequences bk (u)pk are assumed to converge on the bnk (u) = k=0 m=1 interval [0, R), and P(u) is called a degree n Poisson parameter curve with its control points [n] [n] [n] {p0 , p1 , p2 , · · · }. In this paper, we mainly employ the degree 1 Poisson curve. In the sequel, [1] [1] [1] for the sake of brevity, we denote its control points {p0 , p1 , p2 , · · · } as {p0 , p1 , p2 , · · · }, and its basis b1k (u) (k = 0, 1, · · · ) as bk (u) (k = 0, 1, · · · ). Some properties of a Poisson curve are similar to those of a Bézier curve. It is worth pointing out the high-order derivatives formulae, dl P(u) dul = ∞ P bk (u)∆l pk , k=0 l−1 ∆l pk = ∆ 0 ≤ u < R, l = 0, 1, · · · , pk+1 − ∆l−1 pk , ∆0 pk = pk , k = 0, 1, · · · , of a degree 1 Poisson curve [7], where ∆ is the forward difference operator. And its degree elevation formula [5] is, ∞ +∞ X X [n] bk (u)pk = bnk (u)pk , [n] P0 [n] P1 .. . [n] Pk k=0 = k=0 B00 ( n1 ) 0 B10 ( n1 ) B11 ( n1 ) .. .. . . 0 1 1 1 Bk ( n ) Bk ( n ) ··· ··· .. . 0 0 0 ··· Bkk ( n1 ) P0 P1 .. . , Pk where Bkj (t) is the Bernstein basis function. A Poisson curve has de Casteljau-like corner cutting algorithm and the subdivision scheme has the uniform convergence. So some common transcendental curves can be approximated using Poisson subdivision algorithm with a small approximate error as well as a high approximating speed. 3 Fundamental Form of a Poisson Developable Surface Blending P(u) = ∞ P k=0 bk (u)pk with Q(u) = +∞ P bk (u)qk , we construct a ruled surface k=0 r(u, v) = (1 − v)P(u) + vQ(u) = P(u) + vT(u), (u, v) ∈ [0, R) ⊗ [0, 1], (3) X. Zhang et al. /Journal of Information & Computational Science 2: 2 (2005) 415–419 417 where P(u) and T(u) = Q(u) − P(u) are called a directrix and a generator of the ruled surface respectively. r(u, v) is developable if and only if for any u ∈ [0, R), there exist three scalar functions D(u), E(u) and F (u) that are not all zeros simultaneously such that DP0 +ET+F T0 = 0 [9]. There are only three types of developable surfaces: cylinders (including planes), cones and tangent surfaces. 4 Geometric Representation of a Poisson Developable Surface Case A D(u) ≡ 0. In this case, E(u), F (u) are not both zeroes simultaneously such that ET + F T0 = 0. Let e(u) be a unit vector paralleled to T(u). Define l(u) = kT(u)k , then T0 = l0 e + le0 . Therefore T × T0 = le × le0 = 0, i.e., e × e0 = 0. From the Lagrange’s identity, it follows that e0 · e0 = 0, i.e., e0 = 0. This indicates that the direction of T(u) does not change. i l(0) i T(0) = ∆i (q0 − p0 ) = ddu Consequently r(u, v) is a cylinder. Since d du i i e, (qi − pi ) k e, i = 0, 1, · · · . ³ k ´ k kπ 2 sin Particularly, P(u) = (cos u, sin u, 0), T(u) = (0, 0, 1), pk = 2 2 cos kπ , 2 , 0 , qk = 4 4 ³ k ´ k 2 2 cos kπ , 2 2 sin kπ , 1 , k = 0, 1, · · · . Using the Poisson subdivision algorithm, we obtain a 4 4 surface approximating to the right circular cylinder surface. E(u) F (u) Case B D(u) 6= 0. In this case, there exist two functions α(u) = − D(u) and β(u) = − D(u) such 0 0 that P = αT + βT . Thus r(u, v) can be expressed as r(u, v) = A(u) + (v + β)T, (4) where A(u) = P(u) − βT(u) and A0 = P0 − β 0 T − βT0 = (α − β 0 )T. Case B.1 α = β 0 . In this case, A0 = 0; if we introduce a parameter transformation vb = v+β(u) ∈ [β(u), β(u)], then r(u, v) can be represented as r(u, v) = A + vbT(u). (5) It means that r(u, v) is a cone with its constant vertex A. Let α = − exp(−u), β = exp(−u), then +∞ X bi (u)∆pi = − exp(−u) i=0 +∞ X bi (u)(qi − pi ) + exp(−u) i=0 +∞ X bi (u)∆(qi − pi ). i=0 From degree elevation formula and linear independence of Poisson basis, we can obtain qi+1 ¶ i µ X i = pi+1 + 2(qi − pi ) + ∆pj , j i = 0, 1, 2, · · · . (6) j=0 Specially, p(u) = (exp(−u) cos u, exp(−u) sin u, exp(−u))³, α = − exp(−u) and β = exp(−u). So´ ¡ ¢ k k p0 = (1, 0, 1), pk = cos kπ , sin kπ , 0 , q0 = (2, 0, 2), qk = cos kπ + 2 2 cos kπ , sin kπ + 2 2 sin kπ ,1 , 2 2 2 4 2 4 k = 1, 2, · · · . Fig. 1 illustrates the corresponding conical surface through the conical spiral curve (conical logarithmic curve) P(u). 418 X. Zhang et al. /Journal of Information & Computational Science 2: 2 (2005) 415–419 q 0 q3 Q(u) q 1 q2 q2 Q(u) q3 p0 p3 P(u) p2 q 1 P(u) q p1 0 p3 p2 p1 p 0 Fig. 1: A conical Poisson surface Fig. 2: A Poisson tangent surface through a conical spiral. through a cylinder spiral. 1 0 Case B.2 α 6= β 0 . Hence T = α−β b= 0 A . We introduce a new parameter v is a tangent surface of the curve A = A(u), whose expression is v+β(u) , α(u)−β 0 (u) then r(u, v) r(u, v) = A(u) + v̂A0 (u). (1) Let α = 1, β = 0, then we get +∞ P bi (u)∆pi = i=0 +∞ P (7) bi (u)(qi − pi ). Then we obtain i=0 qi = pi+1 , i = 0, 1, · · · . (8) ´ ³ k k kπ 2 sin , 2 , k , qk = Particularly, P(u) = (cos u, sin u, u), α = 1, β = 0. pk = 2 2 cos kπ 4 4 ³ k+1 ´ k+1 2 2 cos (k+1)π , 2 2 sin (k+1)π , k + 1 , k = 0, 1, · · · . So we get a Poisson tangent surface through 4 4 a cylinder spiral, as depicted in Fig. 2. (2) Let α = σ2 , β = σu , σ 6= 0, then we get +∞ X bi (u)∆pi = i=0 +∞ X i=0 +∞ X 2 i bi (u) (qi − pi ) + bi (u) ∆(qi−1 − pi−1 ). σ σ i=1 Based on linear independence of Poisson basis, we obtain ½ 0 q0 = p0 + σ∆p , i = 0; 2 σ∆pi +i(qi−1 −pi−1 ) , i = 1, 2, · · · . qi = pi + i+2 (9) ³ k In particular, P(u) = (cos u − u sin u, sin u + u cos u, 2u), α = 2, and β = u. So pk = 2 2 cos kπ − 4 ´ ³ k+1 k−1 k−1 k−1 k+1 k 2 2 k sin (k−1)π , 2 2 sin kπ + 2 2 k cos (k−1)π , 2k , qk = 2 2 cos (k+1)π − 2 2 k sin (k−1)π ,2 2 4 4 4 4 4 ´ k−1 + 2 2 k cos (k−1)π , 2k + 1 , k = 0, 1, · · · . Now making v̂ = v + u, A = (cos u, sin u, u) sin (k+1)π 4 4 is an edge of regression. Thus r(u, v) = (cos u − (u + v) sin u, sin u + (u + v) cos u, 2u + v) is a tangent surface of the cylinder spiral A(u), as shown in Fig. 3. (3) Let α = u1 , β = 1, then +∞ X i=1 bi (u)i∆pi−1 = +∞ X i=0 bi (u)(qi − pi ) + +∞ X i=1 bi (u)i∆(qi−1 − pi−1 ). X. Zhang et al. /Journal of Information & Computational Science 2: 2 (2005) 415–419 q 419 q3 3 p3 Q(u) q2 Q(u) p3 q p2 2 P(u) P(u) p2 q1 A(u) A(u) p1 p q0 q1 1 p0 q0 p0 Fig. 3: A Poisson tangent surface Fig. 4: A Poisson tangent surface of a cylinder spiral. through an involute spiral. According to linear independence of Poisson basis, we obtain ½ q0 = p0 , i = 0; −2pi−1 ) qi = pi + i(pi +qi−1 , i = 1, 2, · · · . i+1 (10) ³ k k−1 −2 2 k Specially, P(u) = (cos u−u sin u, sin u+u cos u, 2u), α = and β = 1. So pk = 2 2 cos kπ 4 ´ ³ k−1 k+1 k+1 k k k sin (k−1)π , 2 2 sin kπ + 2 2 k cos (k−1)π , 2k , qk = 2 2 cos kπ − 2 2 k sin (k−1)π , 2 2 sin kπ +2 2 k 4 4 4 4 4 4 ´ cos (k−1)π , 3k , k = 0, 1, · · · . We draw a tangent surface through the involute spiral P(u) of 4 a circle, as depicted in Fig. 4. The edge of regression is a cylinder spiral A = P − T = (cos u, sin u, u). 1 u References [1] [2] [3] [4] [5] [6] [7] [8] [9] G. Aumann, A simple algorithm for designing developable Bézier surfaces, Computer Aided Geometric Design 20 (2003) 601-619. R. M. C. Boddulur, B. Ravani, Design of developable surfaces using duality between plane and point geometries, Computer-Aided Design 25 (1993) 621-632. J. S. Chalfant, T. 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