[Bf-funboard] A needed node.

Knapp magick.crow at gmail.com
Tue Jul 2 08:39:14 CEST 2013

Sorry I have not been so clear.  I am home sick and have a fuzzy brain.

On Tue, Jul 2, 2013 at 7:13 AM, David Jeske <davidj at gmail.com> wrote:
> continuing on the topic of "random color" vs "pick random"....
> To get good "artistic" randomly selected colors, I think there needs to be
> a palette table in there somewhere to stay away from muddy randomness. If
> more limited-variance is desired, random values can be plugged into a
> hue/saturation adjuster.

I did my first city by just plugging the random.id into hue and then
desaturating it. Same effect in the end but not the point of my

> Here is an example, both using exactly the same RGBCurves and random
> gamma...
> This first version uses "mathematically random color channels", with a
> "random gamma factor"
> http://www.pasteall.org/pic/54697
> http://www.pasteall.org/pic/54700
> This version uses a "random 5-color pallette selection", with a "random
> gamma factor"...
> http://www.pasteall.org/pic/54698
> http://www.pasteall.org/pic/54699
> The difference is subtle but important.. The "truly random" version has
> muddy mauve and annoying colors which are hard to get rid of. The palette
> colors are easy to control, even with a random gamma factor applied to
> provide more variance. All IMHO of course.

In my example this IS what I want, muddy. I want a node that puts out
a one random number that changes with every instance of the node and
each use of the node, it should also have a seed input. I can see uses
for a lot of other types of nodes, perhaps like noise in OSL. I want
just a standard random function with a seed input and a random number
output. I do now see that there are a lot of possible ways to
implement this.

A real city is rather muddy. On the other hand it has a lot of repeats
of brick and cement. Picking random textures using a random node as
input might be the best way to do a photo real city with particles.

> After these experiments I'm thinking about two things:
> 1) would it be nice to have a "random value" node which is easier to use
> than the modulo node? (I'm thinking yes...since these magical floating
> point divides don't have good mathematical distribution)

Yes, a simple random node is what I want.

> 2) would it be nice to have a slightly different mode for ColorRamp to make
> large palettes easier?   (I'm thinking yes, but could go either way... My
> palette of 5 was easy. Editing a palette of ~30 while keeping it evenly
> spaced would be annoying, but an easy addon could help.)

A palette node is also a great idea but not the one I wanted.

Page 50 to 55 of the osl-languagespec.pdf has a lot of types of output
of the noise pattern generation function that would be great to have
as built in nodes!

Other uses of a random number would be selecting palette choices,
picking textures from a list, making a random point cloud, vectors for
explosions or other random things, to do small adjustments to just
about anything you don't want constant, like green color of a tree's
leaves. The color of gravel pieces.

Douglas E Knapp

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