kurtz le pirate <kur### [at] gmailcom> wrote:


> If i set ambient to zero, it's ok, but renders are differents
> So, what is correct settings for finish {} now ?


See:

http://news.povray.org/povray.newusers/thread/%3Cweb.5098a702d2be5305aaeb765e0@news.povray.org%3E/?mtop=384948&moff=10

for a discussion of this topic, and recommendations by clipka.

Also, see the POV-Ray help topic, and the following entry for emission.


3.6.1.3.1 Ambient

The light you see in dark shadowed areas comes from diffuse reflection off of
other objects. This light cannot be modeled directly using ray-tracing, however,
the radiosity feature can do a realistic approximation at the cost of higher
render times. For most scenes, especially in-door scenes, this is will greatly
improve the end result.

The classic way to simulate Ambient Lighting in shadowed areas is to assume that
light is scattered everywhere in the room equally. The effect can simply be
calculated by adding a small amount of light to each texture, whether or not a
light is actually shining on that texture. This renders very fast, but has the
disadvantage that shadowed areas look flat.

Note: Without radiosity ambient light does not account for the color of
surrounding objects. For instance, when entering a room where the walls, floor
and ceiling are red, your white clothing will look pink from the reflected
light. POV-Ray's ambient shortcut does not account for this.

The ambient keyword controls the amount of ambient light used for each object.
In some situations the ambient light might also be tinted. In that case a color
value can be specified as in the example below:

finish { ambient rgb <0.3,0.1,0.1> } //a pink ambient

If all color components are equal, a single float value may be used. In other
words a single float value of 0.3 is treated as <0.3,0.3,0.3>. The default value
is 0.1, which gives very little ambient light. As with light sources, physically
meaningful values are typically greater than 0, but negative values work too.
Lastly the value can also be arbitrarily high to simulate a very bright light.

You may also specify the overall ambient light level used when calculating the
ambient lighting of an object using the global ambient_light setting.

The total light defined as: Ambient = Finish_Ambient *
Global_Ambient_Light_Source. See also: Ambient Light for more details.

Ambient light affects both shadowed and non-shadowed areas, so if you turn up
the ambient value, you may want to turn down the diffuse and reflection values.

There has been a Change as of version 3.7 in that the ambient mechanism is now
automatically turned off when radiosity is enabled, provided that #version is
set to 3.7 or higher. This will allow use of the same material definitions in
both radiosity and non-radiosity scenes. As a consequence, the practice of
co-opting ambient to model glowing materials will no longer work in radiosity
scenes and is therefore strongly discouraged altogether; instead, the new
emission keyword has been added specifically for this purpose.

Note: Specular reflected indirect illumination like a flashlight shining in a
mirror cannot modeled by either ambient light or radiosity. Use photons instead.

There has been an important Change in version 3.8 regarding the default ambient
setting. When #version is set as either the first statement of the scene file or
via command-line option and the version is 3.8 or greater the default setting is
now ambient 0 as opposed to the ambient 0.1 value used in previous versions.

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