[metapost] Re: Asymptote

Larry Siebenmann laurent at math.toronto.edu
Sat Sep 10 00:13:54 CEST 2005

Hi again John,

     Concerning downloading samples in ".pdf' 
format, you write:

 > Simply clicking on the Asymptote gallery images
 > will download a pdf file. Clicking on the name
 > will show you the source code.

Ok, it's is now working, thanks.

     I note the following comments on 3D in

 | General hidden surface removal will be implemented
 | by using a binary space partition and picture
 | clipping in an upcoming release. 

 | This [graph3] module will be developed into a full
 | three-dimensional graphing package in the near
 | future.

 | Until a complete 3D graphics package [...] is
 | written, a preliminary port of the MetaPost 3D
 | package featpost3D of L. Nobre G., C. Barbarosie
 | and J. Schwaiger to Asymptote makes some 3D
 | functionality already available, as illustrated by
 | the examples near_earth and conicurv.

Are these comments up-to-date?

Where can we find "near_earth.pdf"?

I asked:

>  --- What is your approach to 3D?

and you replied:

 > It's a 3d extension of John Hobby's algorithms on
 > page 131 of Knuths's monograph The MetaFontbook
 > (which I'm planning on submitting to Discrete &
 > Computational Geometry soon). See the surface.asy
 > example and the documentation of the three.asy
 > module to get an idea about what we have done.

It seems you are currently working on wire models
of surfaces since Hobby treated only curves (=
wires). (?)  The sample "conicurv" seems to
involve projection from a finite point onto a
plane --- which in general converts a bezier curve
into a more general NURBS curve. But "conicurv" is
so simple that it would be easy to create it in an
hoc fashion (I haven't examined the code).  Again,
the example named "surface" resorts to piecewise
linear curves.

Will you be supporting NURBS before PostScript
does?  I imagine SVG already supports NURBS. (?)

Concerning the much used ".." and "..." point 
interpolation operators of metapost, it would 
be nice to have a clearer description of what they 
achieve (or try to achieve) -- in terms of 


Laurent S. 

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