Am 05.11.2017 um 23:27 schrieb clipka:
> Am 05.11.2017 um 22:26 schrieb cbpypov:
>> I am rendering an introduction scene for my photonic crystal animation in which
>> spot lights shine on a planar surface. As seen in the attachment, there are
>> these concentric rings. They are even worse because of jpeg chromatic noise.
>>
>> How can I avoid these rings? Normally (e.g. in Photoshop), I'd just add some
>> Gaussian noise to blur the interfaces of the color values (which is there due to
>> the small color gradient). But somehow I could not find out how to add such a
>> "pixel" noise to the texture (and maybe it would be computationally
>> expensive!?).
> 
> Actualy, Photoshop's gaussian blur filter wouldn't help you here: This
> is colour banding from colour quantization.
> 
> What you really need is dithering.
> 
> In POV-Ray v3.6 and earlier, this would have required output to a file
> format with more bits per colour channel (e.g. 16-bit PNG) and
> post-processing in some external piece of software.
> 
> As of v3.7, POV-Ray provides inbuilt dithering via the `+th`
> command-line switch. By default this enables Floyd-Steinberg dithering,
> but alternatives are also available. Most notably, `+thB4` activates 4x4
> Bayer dithering, which may (*) be a better choice for animations.
> 
> (* or may not; I suggest trying both. Probably no need to bother with
> the other alternatives though.)

As a side note, the `+th` switch also enables dithering for the preview
window, but the algorithm used there may differ from the one used in
file output.

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