POV-Ray : Newsgroups : povray.windows : How do I make a torch shine? : Re: How do I make a torch shine? Server Time
18 Jan 2022 18:56:52 EST (-0500)
  Re: How do I make a torch shine?  
From: Alain
Date: 6 Oct 2013 15:09:16
Message: <5251b55c$1@news.povray.org>

> Christian Froeschlin <chr### [at] chrfrde> wrote:
>> Note this newsgroup is for Windows-specific questions
>> (e.g. GUI, installation, command line parameters), you
>> might find more help in povray.newusers
>>> The only problem is: How can I make a torch shine or how should I define the
>>> light source?
>> some pointers:
>> to make an object glow by itself in 3.6: Increase ambient in texture
>> to make an object glow by itself in 3.7 RC: Increase emission in texture
>> In both cases this will make the object appear bright. However,
>> it will not only illuminate its surroundings unless "radiosity" is
>> activated.  An alternative is to define a "light_source" at the position
>> where the torch should emit light. If the light source is within the
>> object you need to add "no_shadow" to the object so the light
>> can actually get out.
> Hm, I can't make this work. I can define the 'ambient' value but I struggle with
> the radiosity setting. How do I write this so it could work?

For a start point using radiosity, just add radiosity{} in your 
global_settings section.
This will turn radiosity on using default parameters. Those parameters 
are a descent starting point.

If the torch flame have some transparency, just adding a regular 
light_source inside ot will work, giving uneven and coloured illumination.

To get beter realism, you should use light fading. Add this:
fade_distance 1 fade_power 2

Adjust the light's intencity to get the illumination you want. There is 
no upper limit to a light's intencity.

To further improve realism, you can concider using an area_light.
The following, added to your light_source definition is a good start:
area_light 1*x 1*z 9 9 adaptive 0 circular orient
Using adaptive is importent to greatly improve the rendering time. It 
allow the use of a LOT of samples without slowing you down to much.

This make the light act like a spherical light with a diameter of 1 unit.

Example using both propositions:

	<0,1.5,0> // the light's location
	rgb 100 // it's colour and intensity, adjusted for the fading
	fade_distance 1 fade_power 2
// physicaly acurate fading demand fade_power 2
	area_light 1*z 1*x 17 17 adaptive 0 circular orient


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