Elias Pschernig <eli### [at] aonat> wrote:
: I still remember from university that f'x(x, y) = 2 * x * y and
: f'y(x, y) = x ^ 2. At (1, 1) this would give me f'x = 2 and f'y = 1 - but
: from there on I'm lost..

  The normal is the cross-product of the vectors <1, 0, f'x(x,y)> and
<0, 1, f'y(x,y)>, that is, vcross(<1, 0, 2>, <0, 1, 1>).

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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