Hi,
I experinece an error in rendering of poly object. Blak pixel lines appear
on polys. Position of lines is dependent on camera position.
I found this bug described
here on news, but bug report does not give any solution of problem. Since it
is a long time ( bug report is from 1999), I want to ask if someone has any
idea
how to solve it or overcome it.

I know that I can use isosurface object as well, but it is about 5 to 10
times slower and much more memory expensive, so when I use many polys I
experience out_of_memory error. (My scenes have about thousands, or tens of
thousnads of polys)

-Is there a patch?
-Could this be cured by changing some parameters in polysolve.c file or
elsewhere?
-Does anybody know why it happens? (i.e. does the black line mean, that
roots were not found by rootfinder?)

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In article <web.3f5a3573cdbfef5d55a148e60@news.povray.org> , "superbus" 
<superbus at seznam dot cz> wrote:

> I experinece an error in rendering of poly object. Blak pixel lines appear
> on polys. Position of lines is dependent on camera position.

Are you sure you don't just have a too low max_trace_level assuming you are
rendering transparent poly objects (of course)?  And did you use "sturm"?

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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If you are using 'sturm' and still getting the problem, it's probably
a precision problem (not necessarily bug) in the poly object.

  If you can represent your objects as meshes (and specially if you need
to copy the same object several times), I recommend trying that.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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Thorsten Froehlich wrote:

> Are you sure you don't just have a too low max_trace_level assuming you are
> rendering transparent poly objects (of course)?  And did you use "sturm"?

I doubt that is the case. See -
http://news.povray.org/povray.bugreports/7728/?tmax=100

I can't recall if a fix was ever submitted for v3.5.1 but there might have
been one.

-- 
Ken Tyler

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In article <3F5### [at] pacbellnet> , Ken <tyl### [at] pacbellnet>  
wrote:

>> Are you sure you don't just have a too low max_trace_level assuming you are
>> rendering transparent poly objects (of course)?  And did you use "sturm"?
>
> I doubt that is the case. See -
> http://news.povray.org/povray.bugreports/7728/?tmax=100
>
> I can't recall if a fix was ever submitted for v3.5.1 but there might have
> been one.

Yes, but as no scene was shown, I assume the "easy" causes.  After all, it
wouldn't be the first time a user misinterpreted a bug report without
knowing the whole background ;-)

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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>> I doubt that is the case. See -
>> http://news.povray.org/povray.bugreports/7728/?tmax=100
>>
yes this looks very similar to my problem, I think.

>Yes, but as no scene was shown, I assume the "easy" causes.

Here goes simple example. Uncoment to get "poly" or "isosurface" version.
In case of poly objects, farer objects get disturbed with black lines.

// start of source file
#include "colors.inc"
camera {
   location  <0, 1, -3>
   look_at   <0, 1, 0>
}
light_source { <-15, 30, -25> color red 1 green 1 blue 1 }
light_source { < 15, 30, -25> color red 1 green 1 blue 1 }

#declare rot = transform{ translate <-1,0,0> /*rotate x*30 rotate y*30
rotate -z*30*/ scale 2}

//************************************************************
//*Polynomial as poly
//************************************************************
#macro polypoly(tr)
poly {
9,
<0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
-0.0555556,0.0833333,0.0277778,-0.0277778,0,0.0833333,-0.0833333,-0.0833333,-0.0277778,0,0,-0.0833333,0.0833333,0.0833333,0.0277778,0,0,0,0.0277778,-0.194444,0.138889,0.268519,0,0,0,0,0,0,0,0,0,0,0,
0.0833333,-0.0833333,-0.0833333,-0.0277778,0,0,-0.25,0.25,0.25,0.0833333,0,0,0,0.25,-0.25,-0.25,-0.0833333,0,0,0,0,0.416667,-0.416667,-0.416667,-0.138889,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
-0.0833333,0.0833333,0.0833333,0.0277778,0,0,0,0.25,-0.25,-0.25,-0.0833333,0,0,0,0,-0.25,0.25,0.25,0.0833333,0,0,0,0,0,-0.416667,0.416667,0.416667,0.138889,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0.0277778,-0.0277778,-0.0277778,-0.00925926,0,0,0,0,-0.0833333,0.0833333,0.0833333,0.0277778,0,0,0,0,0,0.0833333,-0.0833333,-0.0833333,-0.0277778,0,0,0,0,0,0,-0.527778,0.861111,0.861111,-0.712963
>
sturm
bounded_by{box{<0,0,0><1,1,1>}}
clipped_by{bounded_by}

  pigment { checker Blue, White
         scale 0.2
          }
  finish {
        ambient 0.2
        diffuse 0.8
        phong 0.7
    }
    transform{
        translate tr
        transform rot
    }
}
#end

//************************************************************
//*Polynomial as isosurface
//************************************************************
#macro polyiso(tr)
isosurface {
function {
(-0.0555556*x*x*x*y*y*y*z*z*z)+(0.0833333*x*x*x*y*y*y*z*z)+(0.0277778*x*x*x*y*y*y*z)+(-0.0277778*x*x*x*y*y*y)+(0.0833333*x*x*x*y*y*z*z*z)+(-0.0833333*x*x*x*y*y*z*z)+(-0.0833333*x*x*x*y*y*z)+(-0.0277778*x*x*x*y*y)+(-0.0833333*x*x*x*y*z*z*z)+(0.0833333*x*x*x*y*z*z)+(0.0833333*x*x*x*y*z)+(0.0277778*x*x*x*y)+(0.0277778*x*x*x*z*z*z)+(-0.194444*x*x*x*z*z)+(0.138889*x*x*x*z)+(0.268519*x*x*x)+
(0.0833333*x*x*y*y*y*z*z*z)+(-0.0833333*x*x*y*y*y*z*z)+(-0.0833333*x*x*y*y*y*z)+(-0.0277778*x*x*y*y*y)+(-0.25*x*x*y*y*z*z*z)+(0.25*x*x*y*y*z*z)+(0.25*x*x*y*y*z)+(0.0833333*x*x*y*y)+(0.25*x*x*y*z*z*z)+(-0.25*x*x*y*z*z)+(-0.25*x*x*y*z)+(-0.0833333*x*x*y)+(0.416667*x*x*z*z*z)+(-0.416667*x*x*z*z)+(-0.416667*x*x*z)+(-0.138889*x*x)+
(-0.0833333*x*y*y*y*z*z*z)+(0.0833333*x*y*y*y*z*z)+(0.0833333*x*y*y*y*z)+(0.0277778*x*y*y*y)+(0.25*x*y*y*z*z*z)+(-0.25*x*y*y*z*z)+(-0.25*x*y*y*z)+(-0.0833333*x*y*y)+(-0.25*x*y*z*z*z)+(0.25*x*y*z*z)+(0.25*x*y*z)+(0.0833333*x*y)+(-0.416667*x*z*z*z)+(0.416667*x*z*z)+(0.416667*x*z)+(0.138889*x)+
(0.0277778*y*y*y*z*z*z)+(-0.0277778*y*y*y*z*z)+(-0.0277778*y*y*y*z)+(-0.00925926*y*y*y)+(-0.0833333*y*y*z*z*z)+(0.0833333*y*y*z*z)+(0.0833333*y*y*z)+(0.0277778*y*y)+(0.0833333*y*z*z*z)+(-0.0833333*y*z*z)+(-0.0833333*y*z)+(-0.0277778*y)+(-0.527778*z*z*z)+(0.861111*z*z)+(0.861111*z)+(-0.712963)
}
    max_gradient 4
    open
    bounded_by { box { <0,0,0>, <1,1,1> } }
    clipped_by { bounded_by }

      pigment { checker Blue, White
         scale 0.2
          }
  finish {
        ambient 0.2
        diffuse 0.8
        phong 0.7
    }
    transform{
        translate tr
        transform rot
    }
}
#end

//************************************************************
//********************* HERE CHOOSE **************************
//************************************************************

  polyiso(<-0.2,0,0>)
  polyiso(<1,0,5>)
  polyiso(<4,0,10>)

//  polypoly(<-0.2,0,0>)
//  polypoly(<1,0,5>)
//  polypoly(<4,0,10>)

//************************************************************
//************************************************************
plane {y, -2
 pigment {
  checker Yellow, Green
  scale 2
 }
 finish {
  ambient 0.2
  diffuse 0.8
 }
 hollow
 clipped_by{box{<20,20,20><-20,-20,-20>}}
}
// end of source

For explanation waht it represents:
The polynomials are generated. It represents zero level of tricubic
interpolation of
values in 8 vertexes of unity cube. It shall be something like cubic patch
commonly used in surfaces but here it is in one more dimension.

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