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.)

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