Re: [Plplot-general] surface plot questions

[David B. <stu...@gm...>]

Alan,

Thanks for the reply.  MATLAB and SCILAB functions are overloaded to 
allow to this.  For example the following figures were generated by such 
a call to surf(x,y,z), with x, y, and z each a n-by-n matrix.

I believe this causes the function to trace curves of constant u and v, 
though I am not sure.  I use it to make 3-dim cardioid patterns.

I believe the following wound work (with some mods).

u = linspace(min,max,n);

[U,V] = meshgrid(u,u);

define some functions.

X(U,V), Y(U,V), Z(U,V)

then

surf(X,Y,Z).

if u and v are theta and phi in spherical coordinates, then 
sin(Th).*cos(Ph), sin(Th).*sin(Ph), cos(Th) would generate the unit sphere.

Thanks,
David




On 3/20/2018 10:09 PM, Alan W. Irwin wrote:
> On 2018-03-20 17:05-0400 David Bergman wrote:
>
>> All,
>>
>> I am interested in making a surface plot in 3-dim of a parameterized 
>> surface in the following format,
>> x(u,v), y(u,v), z(u,v)
>> rather than the usual z = f(u,v).
>>
>> MATLAB, SCILAB, and Octave have this option and I was wondering if 
>> PLplot has it as well.
>> I did look through the examples and documented interfaces and nothing 
>> seemed to match this.
>>
>
> Hi David:
>
> Our plcont and plshades API's have this capability, see
> <http://plplot.org/docbook-manual/plplot-html-5.13.0/plcont.html> and
> <http://plplot.org/docbook-manual/plplot-html-5.13.0/plshades.html>,
> but our other means of making 3D plots, e.g., plmesh (see
> <http://plplot.org/docbook-manual/plplot-html-5.13.0/tri-d-plots.html>
> for the full list of our 3D API's) have only one-dimensional x and y 
> arguments.
>
> By the way, can you give me an example of, say, a mesh plot of a
> parameterized surface?  I thought such plots required one-dimensional
> x and y vectors since the results are typically a collection of 3D
> lines, z(y)_i, at a fixed set of one-dimensional x_i values and
> another set of 3D lines, z(x)_j, at a fixed one-dimension set of y_j
> values.  In fact, all the MATLAB examples I have just looked up of
> mesh plots seem to be of this type.
>
> Alan
> __________________________
> Alan W. Irwin
>
> Astronomical research affiliation with Department of Physics and 
> Astronomy,
> University of Victoria (astrowww.phys.uvic.ca).
>
> Programming affiliations with the FreeEOS equation-of-state
> implementation for stellar interiors (freeeos.sf.net); the Time
> Ephemerides project (timeephem.sf.net); PLplot scientific plotting
> software package (plplot.sf.net); the libLASi project
> (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
> and the Linux Brochure Project (lbproject.sf.net).
> __________________________
>
> Linux-powered Science
> __________________________
>



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