POV-Ray : Newsgroups : povray.advanced-users : Apparent circular pattern of scratches : Re: Apparent circular pattern of scratches Server Time
25 Feb 2024 01:19:34 EST (-0500)
  Re: Apparent circular pattern of scratches  
From: Bald Eagle
Date: 23 Jan 2019 20:05:01
Message: <web.5c490e395e3f4450765e06870@news.povray.org>
"omniverse" <omn### [at] charternet> wrote:

> I like that crackle pattern idea, I was able to get the effect easily that way
> going with your SDL.
> Just probably needs a randomization of the averaged normal parameters.

I would have never thought that using crackle would give rise to this effect.
I was experimenting with wood and ripples...

> Lighting/specular highlighting changes it drastically too.

Yes, likely so.

This is getting close - something finer, less grainy, and with that "all other
scratches are invisible except the very few that reflect light" would be the
goal.   I'll hopefullly get a chance to try it out on something in a scene and
see how it works.

Also - pretty good for a plane --- now how do we achieve this on the surface of
a a 3D primitive?  Does the crackle / granite already take care of that?

We need a Scratched Sphere on a Checkered Plane scene... :)

Too many things to do lately, but this gave me the nudge to dig through the
source and look at how the crackle pattern is actually implemented, and I found
these comment gems that ought to make their way into the docs:

*   Large scale, without turbulence, makes a pretty good stone wall.
*   Small scale, without turbulence, makes a pretty good crackle ceramic glaze.
*   Highly turbulent (with moderate displacement) makes a good marble, solving
*   the problem of apparent parallel layers in Perlin's method.
*   2 octaves of full-displacement turbulence make a great "drizzled paint"
*   pattern, like a 1950's counter top.
*   Rule of thumb:  put a single colour transition near 0 in your colour map.

Very nice - I'm hoping this effect will get further honed into an include /
macro with a few options, so we can have a new easy-to-use tool for making more
realistic looking hard surfaces.

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