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Not that it matters all that much..
Why do I get a surface here:
isosurface {
function {sqr(x)+sqr(z)-sqr(y)}
contained_by { box { -4,<4,0,4> } }
pigment {rgb y}
}
but not here:
isosurface {
function {sqr(x)+sqr(z)-sqr(y)}
contained_by { box { <4,0,4>,-4 } }
pigment {rgb y}
}
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I've asked myself that question many times. It's always been like that.
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It is just an old convention for describing a box (box{max,min}).
And it seems to have been with us forever. But lets give this
description a try: box { <4,0,4>,-4 }= a box that has
no size in this universe (max. is less then min) but might have
some volume in a non-POVian universe.
Sigmund Kyrre Aas wrote:
>
> Not that it matters all that much..
>
> Why do I get a surface here:
>
> isosurface {
> function {sqr(x)+sqr(z)-sqr(y)}
> contained_by { box { -4,<4,0,4> } }
> pigment {rgb y}
> }
>
> but not here:
>
> isosurface {
> function {sqr(x)+sqr(z)-sqr(y)}
> contained_by { box { <4,0,4>,-4 } }
> pigment {rgb y}
> }
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It may be one of those quirky sort of things, like which math is done
first. I.e. x+y*z or z*y+x or x+(y*z) or... Didn't mean to make math out to
be folly by saying that, sorry :-)
Anyway, I've seen it someplace that it's a good idea to do a box thusly:
-4,4 instead of 4,-4 so that the lower values are put first. Either that or
I'm dreaming it up. Why such a thing would cause a break in it I haven't a clue.
Bob
"Sigmund Kyrre Aas" <as### [at] stud ntnu no> wrote in message
news:3906B42E.4034540E@stud.ntnu.no...
| Not that it matters all that much..
|
| Why do I get a surface here:
|
| isosurface {
| function {sqr(x)+sqr(z)-sqr(y)}
| contained_by { box { -4,<4,0,4> } }
| pigment {rgb y}
| }
|
| but not here:
|
| isosurface {
| function {sqr(x)+sqr(z)-sqr(y)}
| contained_by { box { <4,0,4>,-4 } }
| pigment {rgb y}
| }
|
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"Mr. Art" wrote:
>
> It is just an old convention for describing a box (box{max,min}).
> And it seems to have been with us forever. But lets give this
> description a try: box { <4,0,4>,-4 }= a box that has
> no size in this universe (max. is less then min) but might have
> some volume in a non-POVian universe.
You probably meant box{ -4,<4,0,4> }. Similar to spheres with negative radius I
guess. Strange then that both regular boxes and clipped_by boxes work fine.
sig.
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Why don't just swap the offending coordinates at parse time as needed?
I think that the box primitive does that.
--
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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