[pstricks] projections onto different planes in one picture (second comment)

[Zbigniew Nitecki]

After sending the previous reply to Herbert, I noted some more phenomena which might help someone explain what is going on here.

First, while changing the range of the red curve (ycutfcn) from -1 0 to e.g. -2 0 had no effect,
adding a new curve, identical to this but with range 0 1 (and in my case linestyle=dashed) created a curve on the other side which does go all the way up to the top, as it should.

Second, though, changing the viewpoint was highly informative.  Changing from 
viewpoint=18 65 30 rtp2xyz  to viewpoint=18 80 30 rtp2xyz made it clear that the red curve
is being projected, not onto the red plane, but onto the blue one.
And changing the second coordinate to a value above 80 (eg 105) made the blue plane and all the curves disappear: I got only the red plane.

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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