William F Pokorny <ano### [at] anonymousorg> wrote:
> On 05/29/2014 12:02 PM, xslittlegrass wrote:
> > Hi Le,
> >
> > Thanks for your reply, that's very helpful.
> > But do you know how to smooth a 2d data set so that it is G4 continuity ?
> >
> > Best,
> > xslittlegrass
> >
> I've no easy answer to your question. Perhaps you could use the points
> as input to some form of catmull-rom spline, but most probably the
> result would still not be exactly the curve you want.
>
> Maybe give inkscape (www.inkscape.org) a try. It has an option to draw
> Bezier curves/splines which can be saved to a file as POV-Ray prisms.
> Images can be imported and used as guides as you draw. The spline
> specification in each POV-Ray prism can be used directly with POV-Ray's
> lathe object. Best is that with a program like inkscape you can see your
> curve as you make adjustments.
>
> In Inkscape, after drawing your initial Bezier curve, you can go to an
> "edit paths by points" mode, select sets of points on the curve by
> shift-picking on the points. With the points selected you can then use
> commands at the top like "Make selected nodes smooth" and "Make selected
> nodes auto-smooth" to keep particular points in line so to speak.
>
> When working in POV-Ray's SDL I've found it easiest to use Bezier
> splines which are made up of sets of 4 vertices/points, two end points
> and two internal control points. Larger curves can be made by
> overlapping end points and smoothness at any overlapping end point is
> accomplished by matching the slopes of the nearest two control points to
> the overlapped points.
>
> There are other interactive tools about for creating lathe and prism
> splines including one mentioned currently on the main povray.org web
> site called Epspline, though I have not used that one myself.
>
> Bill P.

Hi Bill,

Thanks a lot for your detailed answer. I can benefit a lot from it.

Actually, I found that when I plot the revolution plot in Mathematica with the
same data, it also
give the roughness on the surface. So I posted the question on stack exchange.
Someone then give a suggestion of just using a Gaussian filter to smooth the
data before plot it.
And it works very well, here is the result:
http://imgur.com/F8l2F0z

And here is the link of the SE post:
http://mathematica.stackexchange.com/questions/48726/how-to-make-a-smooth-revolution-surface-plot


Thanks a lot for your help.

Best,
xslittlegrass

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