Piriform and Halo problem (creating a Flame).

Piriform and Halo problem (creating a Flame).

Post by Gautam N. L » Sat, 19 Jul 1997 04:00:00



Hi,
I am creating a flame for a scene using the Piriform object (part of POV-Ray
package), and I seem to be having problems.

When I rendered the scene, I get this weird garbage
near the middle of the image.  I did many renders, with many different options
(different turbulence, samples, color_map, image size), and I still see this weird
problem.  I haven't seen it on other flames (such as those of Peter Engels).

What's happening?  The source used is shown below.  An example image
(illustrating the problem) is posted at:

http://www.interlog.com/~gautam/flame.jpg

The actual .TGA file is at:
http://www.interlog.com/~gautam/flame.tga

Please take a look, 'cause it's a small image (320x240).  Also, It's not the problem
with the .JPG file nor is it that I continued a previous trace, it actually happened
in the output .TGA file (over and over). I rendered with the +a option at
320x240.

BTW, I tried to render with a gray background (any level), and I couldn't see the
flame at all.  I could see it with other or no colours.

// ---------------------------------------------------------------------------------------------
// FLAME.POV By Gautam N. Lad.
// ---------------------------------------------------------------------------------------------
camera {
    location <0, -1, -2.75>
   direction <0, 0, 1.20711>
         sky <0, 1, 0>
          up <0, 1, 0>
       right <4/3, 0, 0>
     look_at <0, -1, 0>

Quote:}

light_source {  < 4,  2, -5>   color rgb< 1  1  1> }
light_source {  <-4, -2, -5>   color rgb<.5 .5 .5> }
light_source {  < 4, -2, -5>   color rgb<.5 .5 .5> }
light_source {  <-4,  2, -5>   color rgb<.5 .5 .5> }

#declare Piriform =
 quartic
  {< 4,   0,   0,   -4,  0,   0,   0,   0,   0,  0,
     0,   0,   0,    0,  0,   0,   0,   0,   0,  0,
     0,   0,   0,    0,  0,   1,   0,   0,   0,  0,
     0,   0,   1,    0,  0>
  }

#declare Flame =
  halo {
    linear
    planar_mapping
    emitting
    color_map {
    [0.10 color rgbt<1.104 0.969 0.671 0.8810>]
    [0.20 color rgbt<1.104 0.969 0.671 0.8820>]
    [0.30 color rgbf<1.204 0.963 0.677 0.9830>]
    [0.40 color rgbf<1.304 0.963 0.677 0.9840>]
    [0.50 color rgbf<1.404 0.963 0.677 0.2500>]
    [0.60 color rgbt<1.304 0.865 0.670 0.9600>]
    [0.70 color rgbf<1.404 0.866 0.673 0.9870>]
    [0.80 color rgbt<1.404 0.886 0.673 0.9880>]
    [1.00 color rgbf<1.404 0.888 0.886 -.1014>]
             }
  turbulence .8
  samples 12

Quote:}

object {
  Piriform
  pigment { rgbt 2 }
  halo { Flame }
  rotate z*-90
  scale <.575,2,1>
  no_shadow
  hollow

Quote:}

// ---------------------------------------------------------------------------------------------

Bye!

****************************************************
* Gautam N. Lad                                    *
*--------------------------------------------------*
*                                                  *

* Website   : http://www.interlog.com/~gautam      *
*                                                  *
* OS/2, DOS/Windows, Graphics Gallery, Software,   *
* Links, Rayzor Editor/2, POV-Ray, TexturEyes,     *
* POV-PAK and lots lots lots more!!!!!!!           *
****************************************************

 
 
 

Piriform and Halo problem (creating a Flame).

Post by Shawn Fu » Sun, 20 Jul 1997 04:00:00




>>BTW, I tried to render with a gray background (any level), and I couldn't see
>> the flame at all.  I could see it with other or no colours.
>>object {
>>  Piriform
>>  pigment { rgbt 2 }    <--- change to a 1
>>  halo { Flame }
>>  rotate z*-90
>>  scale <.575,2,1>
>>  no_shadow
>>  hollow
>>}
>Well, I fiddled with it for a while, and figured out what the problem is. It
>isn't actually the halo that is the problem, but the Piriform itself. What you
>need to do is use the sturm keyword with it, which uses a more accurate model.
>I marked it out in the above code.

>As for the background thing, I'm not sure why it's doing that.. I'll look into
>it, and get back to you. =)

>Hope that helps!
>Shawn

Alright, it turns out that the trouble with the background was because of your
RGBT setting. It should be a 1 instead of a 2.  I'm not sure what a setting of
2 means, but it was messing it up. I changed it, and it even showed up on
total white, albeit barely.

Hope that helps!
Shawn

---------------------------------------

  http://www.the-spa.com/shawn.fumo/
---------------------------------------

 
 
 

Piriform and Halo problem (creating a Flame).

Post by Michael Smit » Sun, 20 Jul 1997 04:00:00



> Hi,
> I am creating a flame for a scene using the Piriform object (part of POV-Ray
> package), and I seem to be having problems.

> When I rendered the scene, I get this weird garbage
> near the middle of the image.  I did many renders, with many different options
> (different turbulence, samples, color_map, image size), and I still see this weird
> problem.  I haven't seen it on other flames (such as those of Peter Engels).

This is very strange. Without having tried this, the first thing I would
try would
be to add the sturm keyword to your piriform. This could be the problem,
and sturm
makes it calculate high degree polynomials much more accurately.
Idea no.2. Try moving your camera to <0.00001,-1,-2.75>. I think pov-ray
sometimes
has problems with scenes where the camera is right on an axis (this is
unlikely to
be the problem, but try changing it anyway).

Hope this helps you.

Michael Smith

 
 
 

Piriform and Halo problem (creating a Flame).

Post by ENGELS » Sun, 20 Jul 1997 04:00:00


Use the Keywort "sturm" after piriform, then you get the right result.
If you have further problems, then try to rotate the object a little bit
like rotate <0.01,0.01,0.01>
this will help.

Peter

 
 
 

Piriform and Halo problem (creating a Flame).

Post by Drew Perttul » Sun, 20 Jul 1997 04:00:00



> When I rendered the scene, I get this weird garbage
> near the middle of the image.  I did many renders, with many different options
..(cut)..
>  An example image
> (illustrating the problem) is posted at:

> http://www.interlog.com/~gautam/flame.jpg

Add 'sturm' like so:

Quote:> // FLAME.POV By Gautam N. Lad.
> //
..(source cut)..
> #declare Piriform =
>  quartic
>   {< 4,   0,   0,   -4,  0,   0,   0,   0,   0,  0,
>      0,   0,   0,    0,  0,   0,   0,   0,   0,  0,
>      0,   0,   0,    0,  0,   1,   0,   0,   0,  0,
>      0,   0,   1,    0,  0>
       sturm
>   }

And the more accurate root-solver will be used. Has nothing
to do with the flame effect, AFAIK.

--Drew

 
 
 

1. Halo and Piriform problem solved.

Hi,
THANK YOU to all who helped me with this problem!

Bye!

****************************************************
* Gautam N. Lad                                    *
*--------------------------------------------------*
*                                                  *

* Website   : http://www.interlog.com/~gautam      *
*                                                  *
* OS/2, DOS/Windows, Graphics Gallery, Software,   *
* Links, Rayzor Editor/2, POV-Ray, TexturEyes,     *
* POV-PAK and lots lots lots more!!!!!!!           *
****************************************************

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