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Christoph Hormann wrote:
> It's no problem at all to do right-handed geometry in POV,
One may represent the three axes as they appear in povray with one's right
hand, but your coworkers and family members would complain about you
flipping them the bird.
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On Tue, 04 Dec 2001 07:06:15 -0500, Timothy R. Cook wrote:
> I still don't quite get why math (and hence POV) 3D coords use
> left-hand rule; apart from most people being right-handed, CAD
Math uses the right-hand rule too. POV uses the left-hand rule by
default because that's how it was created. Call it a historical
accident. To change it now would just be wrong.
--
#macro R(L P)sphere{L __}cylinder{L P __}#end#macro P(_1)union{R(z+_ z)R(-z _-z)
R(_-z*3_+z)torus{1__ clipped_by{plane{_ 0}}}translate z+_1}#end#macro S(_)9-(_1-
_)*(_1-_)#end#macro Z(_1 _ __)union{P(_)P(-_)R(y-z-1_)translate.1*_1-y*8pigment{
rgb<S(7)S(5)S(3)>}}#if(_1)Z(_1-__,_,__)#end#end Z(10x*-2,.2)camera{rotate x*90}
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"Greg M. Johnson" wrote:
> One may represent the three axes as they appear in povray with
> one's right hand, but your coworkers and family members would
> complain about you flipping them the bird.
...actually I never understood why people even needed to
represent the axes with their hand except for demonstrating
to people who didn't know about them; I have no trouble
picturing the axes in my head.
--
Tim Cook
http://empyrean.scifi-fantasy.com
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------
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"Timothy R. Cook" <tim### [at] scifi-fantasycom> wrote :
>
> ...actually I never understood why people even needed to
> represent the axes with their hand
It's a learning tool... there was a time when you needed to learn it
too, whether you remember it or not.
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On Tue, 04 Dec 2001 08:37:14 -0500, Timothy R. Cook wrote:
> "Greg M. Johnson" wrote:
>> One may represent the three axes as they appear in povray with
>> one's right hand, but your coworkers and family members would
>> complain about you flipping them the bird.
>
> ...actually I never understood why people even needed to
> represent the axes with their hand except for demonstrating
> to people who didn't know about them; I have no trouble
> picturing the axes in my head.
The "right hand rule" is most useful for visualizing which way a
cross product (or, by extension, a rotation) goes. If you can do that
in your head, great, but many otherwise talented people can't.
--
plane{-z,-3normal{crackle scale.2#local a=5;#while(a)warp{repeat x flip x}rotate
z*60#local a=a-1;#end translate-9*x}pigment{rgb 1}}light_source{-9red 1rotate 60
*z}light_source{-9rgb y rotate-z*60}light_source{9-z*18rgb z}text{ttf"arial.ttf"
"RP".01,0translate-<.6,.4,.02>pigment{bozo}}light_source{-z*3rgb-.2}//Ron Parker
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"Timothy R. Cook" <tim### [at] scifi-fantasycom> wrote in message
news:3C0CD18A.968961E9@scifi-fantasy.com...
>I have no trouble
> picturing the axes in my head.
>
Sounds painful, have you been arguing with Bill?
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> And last: Pov is not left-handed. It is half-ambidextrous* :
> default to left hand, but can work without problem with right hand.
This isn't quite true. Lots of the primitives have the y-axis hardcoded as
the "vertical" axis.
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Tom Melly wrote:
> >I have no trouble picturing the axes in my head.
> Sounds painful, have you been arguing with Bill?
...
Er, that would be plural axis, not plural axe. ;)
--
Tim Cook
http://empyrean.scifi-fantasy.com
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------
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Bill DeWitt wrote:
> It's a learning tool... there was a time when you needed
> to learn it too, whether you remember it or not.
The way I learned the axes was by drawing stuff on graph
paper (cheesy game maps mostly), I understood that as XY.
Z was then obviously the elevation.
--
Tim Cook
http://empyrean.scifi-fantasy.com
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------
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Ron Parker wrote:
> Math uses the right-hand rule too. POV uses the left-hand rule by
> default because that's how it was created. Call it a historical
> accident. To change it now would just be wrong.
Hmmm... I don't think on it as an accident. Tim has really given the
answer with the question: CAD programs were done for designers, people
that thinks on floorplans with implicit x-y axis. But which was the
public POV-Ray was created for? IMHO, this is the key...
--
Jaime Vives Piqueres
La Persistencia de la Ignorancia
http://www.ignorancia.org/
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