Hello all,
I need you help with a scene of mine.
Basically i'm trying to modell a "flared" disc of gaz...

The disc is the surface inside a cylinder and between 2 paraboloids...
I fill it with emitting media...

i wanted to tell the code i want more emmiting media to the center of the
disc...i did it with a cylindrical density pattern.

my problem is that bright part of my media is not centered in the disc...it
seems that it has nothing to do with the cylindrical pattern...
i spent many hours trying to understand what i did wrong...i figure it may
be a silly error of mine, but it can also be something i simply did not
understand so i'm requesting your help! :D

i'm looking forward for your advices
jimmy


here's a paste of my scene file:

#include "colors.inc"
#include "functions.inc"
#include "shapes.inc"

//rayons min et max du disque....
#declare r_in = 10;
#declare r_out = 500;


//hauteur min et max du disque
#declare h_min =10;
#declare h_max =80;


//cylinder encompassing the disc
#declare Cube = cylinder{<0,-h_max,0>,<0,h_max,0>,r_out open }  ;




//top and bottom surfaces
#declare top = object{Paraboloid_Y
scale r_out
scale ((h_max-h_min)/r_out)*y
translate h_min*y
}
;

#declare bottom=object{top
rotate 180*x
};





//construction of the flared disc
#declare disque=union{
object{top}
object{bottom}
clipped_by{Cube}
};


#declare Disque=union{
object{Cube}
object{disque}
};




//color map
#declare gradient_disque= color_map{
[0.0 rgb<0.002,0.0,0.0>]

[0.05 rgb<0.03,0.0,0.0>]
[0.1 rgb<0.035,0.0,0.0>]
[0.2 rgb<0.04,0.0,0.0>]
[0.3 rgb<0.05,0.0,0.0>]
[0.4 rgb<0.1,0.0,0.0>]
[0.6 rgb<0.2,0.00,0.00>]
[0.7 rgb<0.3,0.00,0.0>]
[0.8 rgb<0.4,0.0,0.0>]
[0.9 rgb<0.5,0.08,0.0>]
[1.0 rgb<1.0,0.2,0.05>]

}



//object{bottom texture{pigment{color Green}} finish{diffuse 0.6}  }
//object{top texture{pigment{color Green}} finish{diffuse 0.6}  }



//declaration gaz inside the disc
#declare gaz=
interior{
media{
method 3
intervals 1
samples 5
emission 0.01

density{cylindrical scale 500
color_map{gradient_disque}
}

density{wrinkles scale 50
color_map{
[0.0rgb<0.1,0.1,0.1>]
[0.5rgb<0.5,0.5,0.5>]
[1.0rgb<1,1,1>]
}
}

}};


object{Disque
texture {pigment {rgbt 0.5}}
interior{gaz}
hollow}


// perspective (default) camera
camera {location  <000.0, 500.0, -1000.0> look_at   <0.0, 0.0,  0.0>}


//sphere{0,200 pigment{White}}
light_source { <8000,2000,0> rgb 1  }

Post a reply to this message

"jimmy" <nomail@nomail> wrote in message 
news:web.44f8bf5f823370943cba71480@news.povray.org...
> Hello all,
> I need you help with a scene of mine.
> Basically i'm trying to modell a "flared" disc of gaz...
>
> The disc is the surface inside a cylinder and between 2 paraboloids...
> I fill it with emitting media...
>
> i wanted to tell the code i want more emmiting media to the center of the
> disc...i did it with a cylindrical density pattern.
>
> my problem is that bright part of my media is not centered in the 
> disc...it
> seems that it has nothing to do with the cylindrical pattern...
> i spent many hours trying to understand what i did wrong...i figure it may
> be a silly error of mine, but it can also be something i simply did not
> understand so i'm requesting your help! :D
>
> i'm looking forward for your advices
> jimmy
>
>

Not sure what your problem is, but the density is working as should be 
expected.  Try looking from directly above or the side and it is centred 
fine.  I think what you see as off-centred is a result of the angle of view.

-tgq

Post a reply to this message

"Trevor G Quayle" <Tin### [at] hotmailcom> wrote:
> "jimmy" <nomail@nomail> wrote in message
> news:web.44f8bf5f823370943cba71480@news.povray.org...
> > Hello all,
> > I need you help with a scene of mine.
> > Basically i'm trying to modell a "flared" disc of gaz...
> >
> > The disc is the surface inside a cylinder and between 2 paraboloids...
> > I fill it with emitting media...
> >
> > i wanted to tell the code i want more emmiting media to the center of the
> > disc...i did it with a cylindrical density pattern.
> >
> > my problem is that bright part of my media is not centered in the
> > disc...it
> > seems that it has nothing to do with the cylindrical pattern...
> > i spent many hours trying to understand what i did wrong...i figure it may
> > be a silly error of mine, but it can also be something i simply did not
> > understand so i'm requesting your help! :D
> >
> > i'm looking forward for your advices
> > jimmy
> >
> >
>
> Not sure what your problem is, but the density is working as should be
> expected.  Try looking from directly above or the side and it is centred
> fine.  I think what you see as off-centred is a result of the angle of view.
>
> -tgq


Thanks for your answer Trevor.
Yes i saw that face on and edge on the behavior looked fine.
Also  iknew there would be line of sight effect but i estimated they would
not be that big...

i'm confused especially knowing that with a perfect cylinder (Cube in the
code), the media is nicely centered...playing with h_min value i can
transform my flared disc into a cylinder (or very very close
), YET it shows a complete different behaviour from the cylinder...


jimmy

Post a reply to this message

> Thanks for your answer Trevor.
> Yes i saw that face on and edge on the behavior looked fine.
> Also  iknew there would be line of sight effect but i estimated they would
> not be that big...
>
> i'm confused especially knowing that with a perfect cylinder (Cube in the
> code), the media is nicely centered...playing with h_min value i can
> transform my flared disc into a cylinder (or very very close
> ), YET it shows a complete different behaviour from the cylinder...
>
>
> jimmy
>
>

I'm also not quite sure how you are constructing your object, especially 
with the 'open' in the cylinder and the 'clipped_by'.  What should the 
object you are trying to construct look like?

-tgq

Post a reply to this message

to sum up, a cylinder where the top and the bottom faces has been
incurved...in the shape of a parabol

i did this by putting together 2 paraboloids and a cylinder...


"Trevor G Quayle" <Tin### [at] hotmailcom> wrote:
> > Thanks for your answer Trevor.
> > Yes i saw that face on and edge on the behavior looked fine.
> > Also  iknew there would be line of sight effect but i estimated they would
> > not be that big...
> >
> > i'm confused especially knowing that with a perfect cylinder (Cube in the
> > code), the media is nicely centered...playing with h_min value i can
> > transform my flared disc into a cylinder (or very very close
> > ), YET it shows a complete different behaviour from the cylinder...
> >
> >
> > jimmy
> >
> >
>
> I'm also not quite sure how you are constructing your object, especially
> with the 'open' in the cylinder and the 'clipped_by'.  What should the
> object you are trying to construct look like?
>
> -tgq

Post a reply to this message

This seems like some sort of bug to me after running
your code. If you add some other object to the scene
it starts behaving normally. Adding...
sphere {<0,-10000,0>,1 pigment{White}}
and increasing the emission to 0.05 looks OK.

It has something to do with the way you made the
object as well, since...

#declare Disk2 = difference {
   object{Cube}
   object{top}
   object{bottom}
};
object{ Disk2 //Disque
etc

Also looks ok, as the only object in the scene.
Somehow when a ray is cast at Disque it isn't
finding any other objects so it looks different,
probably exits early out of some calculation.

Post a reply to this message

Does replacing

--------code---------
#declare disque=union{
object{top}
object{bottom}
clipped_by{Cube}
};


#declare Disque=union{
object{Cube}
object{disque}
};
------end code-------

with


--------code---------
#declare Disque=difference{
object{Cube}
object{top}
object{bottom}
};
------end code-------

produce what you want?

Abe

"jimmy" <nomail@nomail> wrote:
> Hello all,
> I need you help with a scene of mine.
> Basically i'm trying to modell a "flared" disc of gaz...
>
> The disc is the surface inside a cylinder and between 2 paraboloids...
> I fill it with emitting media...
>
> i wanted to tell the code i want more emmiting media to the center of the
> disc...i did it with a cylindrical density pattern.
>
> my problem is that bright part of my media is not centered in the disc...it
> seems that it has nothing to do with the cylindrical pattern...
> i spent many hours trying to understand what i did wrong...i figure it may
> be a silly error of mine, but it can also be something i simply did not
> understand so i'm requesting your help! :D
>
> i'm looking forward for your advices
> jimmy
>
>
> here's a paste of my scene file:
>
> #include "colors.inc"
> #include "functions.inc"
> #include "shapes.inc"
>
> //rayons min et max du disque....
> #declare r_in = 10;
> #declare r_out = 500;
>
>
> //hauteur min et max du disque
> #declare h_min =10;
> #declare h_max =80;
>
>
> //cylinder encompassing the disc
> #declare Cube = cylinder{<0,-h_max,0>,<0,h_max,0>,r_out open }  ;
>
>
>
>
> //top and bottom surfaces
> #declare top = object{Paraboloid_Y
> scale r_out
> scale ((h_max-h_min)/r_out)*y
> translate h_min*y
> }
> ;
>
> #declare bottom=object{top
> rotate 180*x
> };
>
>
>
>
>
> //construction of the flared disc
> #declare disque=union{
> object{top}
> object{bottom}
> clipped_by{Cube}
> };
>
>
> #declare Disque=union{
> object{Cube}
> object{disque}
> };
>
>
>
>
> //color map
> #declare gradient_disque= color_map{
> [0.0 rgb<0.002,0.0,0.0>]
>
> [0.05 rgb<0.03,0.0,0.0>]
> [0.1 rgb<0.035,0.0,0.0>]
> [0.2 rgb<0.04,0.0,0.0>]
> [0.3 rgb<0.05,0.0,0.0>]
> [0.4 rgb<0.1,0.0,0.0>]
> [0.6 rgb<0.2,0.00,0.00>]
> [0.7 rgb<0.3,0.00,0.0>]
> [0.8 rgb<0.4,0.0,0.0>]
> [0.9 rgb<0.5,0.08,0.0>]
> [1.0 rgb<1.0,0.2,0.05>]
>
> }
>
>
>
> //object{bottom texture{pigment{color Green}} finish{diffuse 0.6}  }
> //object{top texture{pigment{color Green}} finish{diffuse 0.6}  }
>
>
>
> //declaration gaz inside the disc
> #declare gaz=
> interior{
> media{
> method 3
> intervals 1
> samples 5
> emission 0.01
>
> density{cylindrical scale 500
> color_map{gradient_disque}
> }
>
> density{wrinkles scale 50
> color_map{
> [0.0rgb<0.1,0.1,0.1>]
> [0.5rgb<0.5,0.5,0.5>]
> [1.0rgb<1,1,1>]
> }
> }
>
> }};
>
>
> object{Disque
> texture {pigment {rgbt 0.5}}
> interior{gaz}
> hollow}
>
>
> // perspective (default) camera
> camera {location  <000.0, 500.0, -1000.0> look_at   <0.0, 0.0,  0.0>}
>
>
> //sphere{0,200 pigment{White}}
> light_source { <8000,2000,0> rgb 1  }

Post a reply to this message