POV-Ray : Newsgroups : povray.general : "Insidedness" and Hollow-problems? Server Time
5 Aug 2024 00:20:45 EDT (-0400)
  "Insidedness" and Hollow-problems? (Message 1 to 3 of 3)  
From: Tim Nikias
Subject: "Insidedness" and Hollow-problems?
Date: 19 Jan 2003 17:11:46
Message: <3e2b22a2@news.povray.org>
So, here's what I've just discovered while fumbling with some
of my mesh-modifying-macros to model some new flowers for
my Worldbowl image...

When I take two sides of a petal (top and bottom), which line
up at the rim and thus enclose a volume, I get strange and
unexpected results, and I'd like to know the reason...

When I use smooth or plain triangles for both sides and put them
inside one mesh-statement, the interior isn't calculated properly,
and media doesn't "behave" (even tiny amounts of emission-media
add up to white).
When I use both sets as meshes themselves and put them in a
union, it works, the inside gets filled with media.

There are some artifacts in either version, which I know happens when
POV-Ray traces a triangle which isn't hit properly (when the tracing ray
runs on the triangle, for example), and this can be overcome in some
manner I guess. But that isn't the issue.

I'm wondering: why do two different 2d-shapes add up properly, but one
nice and correctly set mesh doesn't? I'd like to know the reason for this.
Just for future usage and perhaps to avoid in with other macros...

--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde


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From: Warp
Subject: Re: "Insidedness" and Hollow-problems?
Date: 19 Jan 2003 17:41:08
Message: <3e2b2983@news.povray.org>
A complete and minimal scene which demonstrates the problem would be of
great aid when trying to answer your questions.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -


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From: Tim Nikias
Subject: Re: "Insidedness" and Hollow-problems?
Date: 19 Jan 2003 17:59:03
Message: <3e2b2db7$1@news.povray.org>
Heh... :-) You're right about that one. I'll try to come up with one,
but I've found something else which might be the cause, which is
kinda confusing...

I've declared the mesh/union of triangles/two meshes and then placed
this one in a loop to create the flower. But instead of using
object{ ... } I've used union{ ... }, and though it placed the objects, it
seems to have been the cause of the unexpected behaviour. I'll try to fumble
with it some more, then post a minimal scene...

I don't know why I expect people to have an idea what might be
happening without having a scene to fumble themselves... Perhaps my
brain just doesn't accept that others can't intuitively understand and
rebuild what my problem is... ;-)

--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde

>   A complete and minimal scene which demonstrates the problem would be of
> great aid when trying to answer your questions.
>
> --
> #macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
> N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
> N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -


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