Re: [Gnuplot-info] plot 2D circle in 3D graph

[jody <jod...@gm...>]

HI Amir

if your plane equation is p*x + q*y +r*z + d = 0,
then two orthogonal vectors in your plane are for example a=(q, -p, 0)
and b=(p*r, q*r, -(p^2+q^2))
Usually it is a good idea to scale those vectors to unit length

Jody


On Wed, Apr 20, 2011 at 5:13 PM, jody <jod...@gm...> wrote:
> Hi Amir
>
> To display the plane you have to find its parametric description, i.e.
> x = a1*u+b1*v+c1
> y = a2*u+b2*v+c2
> z = a3*u+b3*v+c3
>
> in other words, you have to find two vectors a=(a1, a2, a3) and b=(b1, b2, b3)
> spanning your plane, as well as the offset c=(c1,c2,c3)
>
> then you can plot your plane like that
>
>  splot [u=-5:5] [v=-5:5] a1*u+b1*v+c1, a2*u+b2*v+c2, a3*u+b3*v+c3
>
> simple example
>  x = u
>  y = v
>  z = 3
>
> the you plot it lie this:
>
>  splot [u=-5:5] [v=-5:5] u, v, 3
>
> Jody
>
>
> On Wed, Apr 20, 2011 at 4:22 PM, Amir Sabbagh <ami...@gm...> wrote:
>> Hi Jody,
>> thank you very much for the answer, it helped a lot.
>> is it possible to dispklay both the circle and the plane?
>>
>> On 20 April 2011 13:52, jody <jod...@gm...> wrote:
>>>
>>> Hi Amir
>>>
>>> Yes. For patametric curves you first have to type
>>>
>>>  set parametric
>>>
>>> next set your constants
>>>  R=5
>>>  d=4
>>>  e=6
>>>  c=15
>>>
>>> and then do the plotting (splot is for 3d plots)
>>>  splot [t=0:2*pi]  d+R*cos(t), e+R*sin(t),c
>>>
>>> Hope this helps
>>> Jody
>>>
>>> On Wed, Apr 20, 2011 at 12:28 PM, Amir Sabbagh <ami...@gm...> wrote:
>>> > Thank you Jody for the tip. The problem with this option is that I get a
>>> > "undefined variable: t" error when I try to splot it.
>>> > Maybe there is a workaround for this?
>>> >
>>> > Amir
>>> >
>>> > On 20 April 2011 12:00, jody <jod...@gm...> wrote:
>>> >>
>>> >> Hi Amir
>>> >>
>>> >> You could try a parametric version of your circle:
>>> >>  x = d+R*cos(t)
>>> >>  y = e+R*sin(t)
>>> >>  z = k
>>> >>
>>> >> This gives you a horizontal circle centered at (d,e,k)
>>> >> For a tilted circle you would have to apply rotations
>>> >> around the x and/or y axis.
>>> >>
>>> >> Jody
>>> >>
>>> >>
>>> >> On Wed, Apr 20, 2011 at 11:36 AM, Amir Sabbagh <ami...@gm...>
>>> >> wrote:
>>> >> > Hi you all,
>>> >> >
>>> >> > I am trying to plot a circle and a plane with splot.
>>> >> >
>>> >> > I would like to have a circle at a Z=const value. I have tryed with
>>> >> > ternary
>>> >> > operation with no success.
>>> >> >
>>> >> >   splot a*x+b*y+c title "Plane", \
>>> >> >   (x-d)**2 + (y-e)**2 - R**2==0? ((x-d)**2 + (y-e)**2 - R**2): 0/0
>>> >> > with
>>> >> > title "Circle"
>>> >> >
>>> >> > Can someone enlight me?
>>> >> >
>>> >> > Thank you
>>> >> > Amir
>>> >> >
>>> >> >
>>> >> > --
>>> >> > **************************************************************
>>> >> > Amir Sabbagh
>>> >> > Il mio sito / My site: http://almucantarat.altervista.org
>>> >> > **************************************************************
>>> >> >
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>>> >
>>> > --
>>> > **************************************************************
>>> > Amir Sabbagh
>>> > Il mio sito / My site: http://almucantarat.altervista.org
>>> > **************************************************************
>>> >
>>> >
>>
>>
>>
>> --
>> **************************************************************
>> Amir Sabbagh
>> Il mio sito / My site: http://almucantarat.altervista.org
>> **************************************************************
>>
>>
>