On 11/13/2012 07:58 PM, Bernard LUCE wrote:
>
> Hi everybody !
>
> Hereby, three ways to define-and-draw the O centered torusin plan
> x-y(R=3 ; r=1/2) and three concerns. Cheers !
>
> 1?with implicit cartesian equation :
>
> *load(draw)$*
>
> *draw3d(implicit(x^2+y^2+z^2+8.75=6*sqrt(x^2+y^2),x,-3,3,y,-3,3,z,-.5,.5));*
>
> inconvenience : no smooth appearence. Which options can improve that ?
>
> 2? with cartesian parametric coordinates :
>
> *draw3d(parametric_surface((3+.5*cos(a))*cos(t),
> (3+.5*cos(a))*sin(t), .5*sin(a), a, 0, 2*%pi, t, 0, 2*%pi) ); *
>
> inconvenience : smooth surface but z-axis strechted and finally
> distorted appearance. Same question ?
>
> 3? with cylindrical coordinates :
>
> *draw3d(cylindrical(3+sqrt(0.25-z^2),z,-.5,.5,az,0,2*%pi),cylindrical(3-sqrt(0.25-z^2),z,-.5,.5,az,0,2*%pi));*
>
> **
>
> inconvenience : the same as 2?
>
>
Try this:
plot3d ([(3+.5*cos(a))*cos(t), (3+.5*cos(a))*sin(t), .5*sin(a)], [a, 0,
2*%pi], [t, 0, 2*%pi], [grid,30,30],[z, -2, 2]);
you can change the values for grid and z to your taste.
Cheers,
Jaime