Le 19-02-09 à 12:15, ingo a écrit :
> Quite often I run ito the problem that polygons won't render because not
> all the points are on the same plane. Today I figured out how to fix
> that, scene below, but is there a more efficient way?
> 
> 
> ---%<------%<------%<---
> #version 3.7;
> global_settings{ assumed_gamma 1.0 }
> #default{ finish{ ambient 0.1 diffuse 0.9 }}
> #include "math.inc"
> #include "transforms.inc"
> 
> camera {
>    perspective angle 5
>    location  <0 , 10 ,-10>
>    look_at   <0,0,0>
> }
> light_source{< 500,3000,-500> rgb 1}
> light_source{<-3000,3000,-3000> rgb .5}
> 
> #declare Point=array[6]{
>    <0.429381,-0.055167, 0.379816>,
>    <0.516580,-0.092380, 0.240426>,
>    <0.291647,-0.556033,-0.000017>,
>    <0.185583,-0.627011, 0.044906>,
>    <0.097999,-0.570008, 0.205955>,
>    <0.172851,-0.214639, 0.501546>,
> };
> #declare Normal = <0.614179,-0.577098,0.538277>;
> 
> // distance from the first point to the plane
> #declare Distance = vdot(Normal,Point[0]);
> #declare T = transform{translate Normal*Distance};
> #for(I,0,dimension_size(Point,1)-1,1)
>    // push the points to the aligned plane
>    #declare Point[I] = VProject_Plane(Point[I], Normal);
>    // translate them to their 'original' positions
>    #declare Point[I] = vtransform(Point[I], T);
> #end
> 
> polygon{
>    7,
>    Point[0]
>    Point[1]
>    Point[2]
>    Point[3]
>    Point[4]
>    Point[5]
>    Point[0]
>    pigment{rgb 1}
> }
> sphere{0,0.01 pigment{rgb x}}
> 

If you create your polygon on the X-Y plane, you won't have any problem. 
Then, it's just a mater of rotating it as needed :

#declare Point=array[6]{
   <0.429381,-0.055167>,
   <0.516580,-0.092380>,
   <0.291647,-0.556033>,
   <0.185583,-0.627011>,
   <0.097999,-0.570008>,
   <0.172851,-0.214639>,
};

polygon{
   7,
   Point[0]
   Point[1]
   Point[2]
   Point[3]
   Point[4]
   Point[5]
   Point[0]
   pigment{rgb 1}
   rotate Some_Rotation
}

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