Descriptions and Examples for the POV-Ray Raytracer by Friedrich A. Lohmüller
Design of the Interior of transparent Shapes in POV-Ray
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- POV-Ray Tutorial

  Content Overview
  material, interior, media

  - Syntax material
      texture + interior
  - Window Glass
      + max_trace_level
  - Fog, Mist or Haze
  - Syntax Media
  - Media+Density Maps
  Atmospheric Media
    with/without density map
  - Beames in the Fog
  Object Media
  Emitting Media
  - Light Sword
  - Candle Flames
  Scattering Media
  - Light through Window
  - Steam, Smoke, Clouds
  Absorbing Media
  - Dust Devils
  Special Problems with Media
  - Scaling of Media
  - Overlapping Media

Candle Flames
by Emitting Media

Using "media emission" keyword
for the simulation of a burning candle's flame.

Candle flames by media emission.

With media emission we can simulate burning candle flames. The container object we use (here: an egg shape) should be clear and made hollow (allows media and for effects inside!). The shape can be scaled together with the media to a candle flame shape.
Note: The color of the "emitted" Light is specified after the "emission" keyword. But "media" not really "emit" light - it only means that it's visible without any extern illumination!
If we want the media shining with casting shadows etc., we have to put an additional light_source in the center!

// -----------------------------------------
#local Flame__Shape =
merge{    // egg
   box{<-1,-D,-1>,< 1,1  ,1>}
   scale <1,2.5,1>}
   box{<-1,-1 ,-1>,< 1,0+0.01,1>}
} // end of merge
// -----------------------------------------
#local C__Flame =
  pigment{ color rgbf<1,1,1,1>}// clear!
  finish { ambient 0 diffuse 0 }
  interior {
    media {
      emission color rgb<1.0,0.75,0.1>*1.75
      intervals 9
      samples 1, 20
      confidence 0.9999
      variance 1/100
      density{ spherical
               turbulence 0.15
               color_map {
               [0.0 color rgb <0.0,0.0,0.0>]
               [0.6 color rgb <0.8,0.3,0.0>]
               [0.9 color rgb <1.0,0.8,0.3>]
               [1.0 color rgb <1.0,1.0,0.1>]
                         } // end color_map
            scale <1,2.5,1>
          } // end of density
    }//end of media

media with simple spherical density_map and visible containter object - not scaled!
media with simple spherical density_map, scaled to flame shape.
The Inner Glowing media:
A density map with "crackle" cutted by second a spherical density map with soft borders.
    emission color rgb<1.0, 0.75, 0.1>*2.75
    intervals 3
    samples 32
    method 3
    aa_threshold 0.1 aa_level 5
    density{ crackle  turbulence 0.3
             scale 0.75 translate<0,24,0>
             color_map {
                    [0 rgb 0]
                    [0.00 rgb 0]
                    [0.07 rgb 1]
                    [0.10 rgb 1]
                    [0.12 rgb 0]
                    [1.00 rgb 0]
              } // end color_map
           } // end density
     density{ spherical
              color_map {
                    [0 rgb 0]
                    [0.7 rgb 1]
                    [1 rgb 1]
                } // end color_map
            } // end density
 }// end media
Added an inner glowing area with a second media with a crackle cut with soft borders by another spherical density map.
If we want the candle to shine, we should add a lightsource to the flame shape,
(note: "emission media" does not really shine!)
to get soft shadow borders we take an area_light which intensity is controlled by a number up from 0.
#if(Shining__On > 0) //---------------------
   color rgb <0.8, 0.5, 0.2>*Shining__On
   area_light       // kind of light source
   <0,0,0><0,0.25,0>//lights spread area
   1, 10      // total number of lights x,y
   adaptive 3 // 0,1,2,3...
   jitter // adds random softening of light
} //---------------- end of area_light -----
#end // of "#if(Shining__On>0)"
Added a soft area_light to let the candles really shine!
Scene description for POV-Ray:
"candle_flame_4.txt" or "candle_flame_4.pov"

For more realism it's a good idea to make the light source more wide and also to add a second "area_light" rotated by 90 degrees.
Another proposition by Thierry Banel:
With "fade_distance" and "fade_power" we can simulate the fading of the candle light at relatively short distance.  
This object is available as a ready-made object for POV-Ray
here: Burning Candle
More realistic: "area_light" + "Fade_Distance" + "Fade_Power"!
Include file and samples for POV-Ray see "Candle_2" at
Ready-made Objects

© Friedrich A. Lohmüller, 2012