POV-Ray : Newsgroups : povray.general : quadratic spline problem for 3.1e Server Time
11 Aug 2024 19:34:16 EDT (-0400)
  quadratic spline problem for 3.1e (Message 1 to 4 of 4)  
From: Johan Eriksson
Subject: quadratic spline problem for 3.1e
Date: 8 Jun 1999 12:03:12
Message: <375D3EC5.E5FD9BC3@oc.chalmers.se>
Have anyone else had any problems with quadratic spline?

The following code gives me what is going to be a chalice but when I
render the image everything gets 'striped'. The image seems to be
partially rendered.

Some of the problems disapear when I turn off the orthographic feature
of the camera.

I am using povray 3.1e compiled on a SGI O2 running IRIX 6.3

Any help would be appreciated.


Regards 

/Johan


#include "colors.inc"
#include "textures.inc"
#include "shapes.inc"

camera {
        location <0, 6.5, -30>
        look_at <0, 6.5, 0>
        orthographic
}

light_source {
        <20, 10, -100>
        color White
}

#declare chal =
lathe {
        quadratic_spline
        8,
        <14, 11>, <8.5, 8.5>,
        <6.5, 4.5>, <6, 0>, <5, -0.5>,
        <3.5, 0>, <2, 0>, <1, 0>
}

object {
        chal
        pigment { color White }
}


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From: Ken
Subject: Re: quadratic spline problem for 3.1e
Date: 8 Jun 1999 12:31:06
Message: <375D4227.E49D8EDA@pacbell.net>
Johan Eriksson wrote:

> Any help would be appreciated.
> 
> Regards

Add the sturm modifier and your problem will go away.

#declare chal =
lathe {
        quadratic_spline
        8,
        <14, 11>, <8.5, 8.5>,
        <6.5, 4.5>, <6, 0>, <5, -0.5>,
        <3.5, 0>, <2, 0>, <1, 0>sturm
}


-- 
Ken Tyler

mailto://tylereng@pacbell.net


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From: Johan Eriksson
Subject: Re: quadratic spline problem for 3.1e
Date: 8 Jun 1999 13:52:11
Message: <375D5851.A1AD4648@oc.chalmers.se>
Ken wrote:
> 
> Johan Eriksson wrote:
> 
> > Any help would be appreciated.
> >
> > Regards
> 
> Add the sturm modifier and your problem will go away.
> 
> #declare chal =
> lathe {
>         quadratic_spline
>         8,
>         <14, 11>, <8.5, 8.5>,
>         <6.5, 4.5>, <6, 0>, <5, -0.5>,
>         <3.5, 0>, <2, 0>, <1, 0>sturm
> }
> 
> --
> Ken Tyler
> 
> mailto://tylereng@pacbell.net


Excellent!! Thank you very much.

Do you have any idea why sturm makes thing better (I have not read the
user guide that careful).

/Johan


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From: Ken
Subject: Re: quadratic spline problem for 3.1e
Date: 8 Jun 1999 20:34:16
Message: <375DB32F.B742D2F7@pacbell.net>
Johan Eriksson wrote:

> Excellent!! Thank you very much.
> 
> Do you have any idea why sturm makes thing better (I have not read the
> user guide that careful).
> 
> /Johan

 The docs mention that for speed considerations some objects that use high
order math equations to solve them they use less than accurate methods to
find the solution. The sturmian root solver forces Pov to use a more accurate
method to find the solution and there are times you will see an improvement
in the objects appearance as a result.

-- 
Ken Tyler

mailto://tylereng@pacbell.net


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