Re: [Gnuplot-py-users] parametric surface plots...

[<kai...@t-...>]

Andy Schmeder wrote:

>I want to make parametric surface plots, but I can't figure out how to do
>it with Gnuplot.py.  I've seen plenty of examples done with gnuplot
>functions, but... how to provide my own data?
>
>I can do something like this: (pseudocode)
>
>u = aspan(-0.5*Pi, 0.5*Pi, 100)
>v = aspan(0, 2.0*Pi, 100)
>uv = cartesian_product(u, v)
>g('set parametric')
>g.splot(GridData(cos(uv[0])*cos(uv[1]), cos(uv[0])*sin(uv[1]), sin(uv[0]),
>type='lines'))
>
>Sure enough, it plots a sphere as expected, but its a line trace not a
>true surface, e.g. it can't hide backfaces...
>  
>

I think you are just missing g("set hidden").  The following plots a 
sphere for me with hidden-line removal:

import math
import Gnuplot, Numeric, raster
from Numeric import NewAxis

theta = raster.raster(0, math.pi, 18, 0, 19)
phi = raster.raster(0, 2.0 * math.pi, 36, 0, 37)

xyz = Numeric.zeros((len(theta), len(phi), 3,), Numeric.Float64)
xyz[:,:,0] = Numeric.sin(theta[:, NewAxis]) * Numeric.cos(phi[NewAxis, :])
xyz[:,:,1] = Numeric.sin(theta[:, NewAxis]) * Numeric.sin(phi[NewAxis, :])
xyz[:,:,2] = Numeric.cos(theta[:, NewAxis]) + (phi[NewAxis, :] * 0)

g = Gnuplot.Gnuplot()
g('set parametric')
g('set hidden')
g('set data style lines')

g.splot(xyz)

raw_input("Press return to continue")

Hope this helps,
Michael

-- 
Michael Haggerty
mh...@al...