[pstricks] projections onto different planes in one picture

Zbigniew Nitecki zbigniew.nitecki at tufts.edu
Tue Aug 31 02:24:04 CEST 2010

Thanks again.  Of course this output is superior to the previous, but (I think like you) I remain puzzled by why the order of giving the planes and projections made the second curve show up.

There is now also a new puzzle:  while the range for the red curve in your code is from -1, the curve actually starts much later (the function in question, 4*x*x, should be as high at x=-1 as the other, blue curve (y*y) is at y=2.  But it isn't.  Equally mysterious is the fact that when I tried to change the range of the function ycutfcn (the red curve) from -1 0 to -2 0, which should have had a huge effect, it had no effect whatsoever.  I get the same curve whether the range is -1 0, -1.5 0, or -2 0.

OK, I am not going to use the opacity option, but my reason for using opacity =0 was to try to make the two planes transparent, or at least translucent.  Again, the use of opacity appears to have no effect in the context of this example.

This example appears to me curiouser and curiouser, as Alice would have said...  :-)

Zbigniew Nitecki
Department of Mathematics
Tufts University
Medford, MA 02155

telephones:
Office    (617)627-3843
Dept.    (617)627-3234
Dept. fax    (617)627-3966
http://www.tufts.edu/~znitecki/

On Aug 30, 2010, at 16:56, Herbert Voss wrote:

> Am 30.08.2010 15:43, schrieb Zbigniew Nitecki:
>> Thanks, Herbert.
>> I hope that my inclusion of the picture doesn't make this too large to post (I
>> am not so adept at posting a picture on my web page).
>>
>> This eliminates the \psset{plan=??}, and (after some fiddling) I managed to get
>> the two planes intersecting properly. However, while the first projected curve
>> (blue) shows up fine, the second (red) does not. This is true even if I comment
>> out all references to the first (blue) plane and the curve on it. I thought that
>> maybe it was projecting on the "back side" of the red plane, but it fails to
>> appear whether I rotate it 180 degrees or not.
>
> do not use opacity=0, use a value > 0 or didn't use the option.
> 0 means totally transparent, which is the same as not seen.
>
> However, I do not really understand, why changing the
> order of the two planes helped. It was more a trial and error
> methode to find a working example than understanding the
> problem ...
>
> \documentclass[11pt]{article}
> \usepackage{pst-solides3d}
>
> \begin{document}
> \begin{pspicture}(-3,-1.5)(3,5.5)
> \psset{unit=0.35,lightsrc=40 50 50,viewpoint=18 65 30 rtp2xyz,solidmemory}
> \psSolid[object=plan,
> definition=equation,
> args={[1 0 0 0] 90},
> base=-2 2 -0.5 4.5,
> fillcolor=blue!10,
> name=xplane,
> ngrid=10 10,
> action=none
> ]
> \psSolid[object=plan,
> definition=equation,
> args={[0 1 0 0] 180},
> base=-2 2 -0.5 4.5,
> fillcolor=red!10,
> name=yplane,
> ngrid=10 10,
> action=none
> ]
> \psSolid[object=fusion,
> base=xplane_s yplane_s,
> ]
> \composeSolid%
> %
> \psSolid[object=plan,
> definition=equation,
> args={[0 1 0 0] 180},
> base=-2 2 -0.5 4.5,
> name=yplane,
> linewidth=0.5pt,
> ngrid=10 10,
> action=none,
> ]
> \psSolid[object=plan,
> definition=equation,
> args={[1 0 0 0] 90},
> base=-2 2 -0.5 4.5,
> name=xplane,
> ngrid=10 10,
> action=none,
> ]
> \defFunction[algebraic]{xcutfcn}(y){y*y}{}{}%
> \psProjection[object=courbe,
> linecolor=blue,
> linewidth=2pt,
> plan=xplane,
> range=0 2,
> resolution=720,
> function=xcutfcn,
> action=draw**,
> ]
> \defFunction[algebraic]{ycutfcn}(x){4*x*x}{}{}%
> \psProjection[object=courbe,
> linecolor=red,
> linewidth=2pt,
> plan=yplane,
> range=-1 0,
> resolution=720,
> function=ycutfcn,
> action=draw**,
> ]
> \end{pspicture}
>
> \end{document}
>
>
> Herbert
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